Annual Report 2000 - JuSER

|Di{|~U~ Ć[ ~@{n~ h/\ |k~~\~

Annual Report 2000

Institut für Kernphysik and COSY Research

EDITORIAL BOARD:

Prof. Dr. G . BaurProf. Dr. D . FilgesProf. Dr. K. KilianProf. Dr. R. MaierDr. P . von RossenProf. Dr. K. SistemichProf . Dr. J . SpethProf. Dr. H . StröherandProf. Dr. H . Freiesleben, TU Dresden

Cover picture

Depicted is the EDDA detector residing inside one of the straight telescopic section ofthe COSY ring . This installation surrounds a thinned down section of an aluminiumbeam pipe with scintillators that give information on the scattered particles . Radiatingon each end are photo multipliers that are connected via light guides to thesescintillators . This installation was the first internal experiment and allowed highprecision excitation functions of proton-proton elastic scattering in the kinetic energyrange 0 .5-2.5 GeV. Spin-averaged and spin-dependent differential cross sections aremeasured continuously during acceleration and deceleration of the COSY beam . Thisuniversal detector played a pivotal role in the development of polarized proton beamsinside COSY. A plot showing the achieved polarization level versus momentum isshown on page 145 .

Preface

The present annual report summarizes the research at the Cooler Synchrotron (COSY) at theForschungszentrum Jülich (FZJ) and in particular it covers the activities of the Institut fiirKernphysik (IKP) at COSY and various external research facilities for the year 2000.

When browsing through the pages you will realize that COSY has been doing exceptionallywell . The accelerator delivered proton beams - unpolarized or polarized, electron orstochastically cooled, slowly or fast extracted - for internal and external experiments withremarkable reliability. The total operation time of COSY during the year again was close to7500 hours . Important milestones like the acceleration of polarized protons up to themaximum energy (see also picture on the front page) and the acceleration of a deuteron beamup to 3 GeV/c have been achieved . Thus it is now possible to perform experiments withdeuteron projectiles, eventually also polarized . Ultrafast extraction has been developed so thatproton bursts of 2x109 particles could be delivered to the JESSICA-experiment within a few100 ns. Another breakthrough was attained for the polarized source, which allowed runningfor 70 days for experiments without service of its inner parts . The superconducting test cavityfor the ESS linac has been set up and first tests were performed .

The experiments at the internal and external target positions of COSY have made use of theproton beam for more than 6100 hours . You will find many interesting and exciting results ofthese measurements in the pages to follow. ANKE has obtained differential cross sections andcross section ratios for K+-production at subthreshold energies . COSY-11 and TOF havecontinued their investigations of strangeness production in proton-proton collisions. EDDAhad a long and sucessful run measuring spin correlation coefficients in double polarizationexperiments, making use of their polarized atomic beam source. GEM at BIG KARL haslooked for isospin symmetry breaking in pion production reactions . MOMO has carried on itsdata taking for K+K" production in proton-deuteron reactions . For the first time an experimentat COSY has come to an end: the COSY-13 measurements have been completed with asuccessful run on hypernuclei production in proton-nucleus interactions, using gold anduranium targets . In the meantime the setup has been dismantled to allow mounting of a newexperiment. ESS related activities have become more important: for example a newexperiment at an external target position has been set up (JESSICA) in order to study andoptimize a test version of what will be the ESS target station .

Members of the institute are participating in external experimental collaborations, too : inATRAP at the AD (CERN, Switzerland) [anti-hydrogen], in EUROBALL (Legnaro, Italy)[nuclear spectroscopy], at PSI (Villigen, Switzerland) [pionic atoms], with TAPS at MAMI(Mainz, Germany) [photonuclear reactions], in WASA at CELSIUS (Uppsala, Sweden)[hadronic interactions], in ZEUS at DESY (Hamburg, Germany) [elementary particle physics]and at GSI (Darmstadt, Germany) [atomic physics] . Results of these activities are also foundbelow.

The theory group of the institute has been very active in a broad range of research fields . Itsfocus, however, is on hadronic physics in the realm of non-perturbative QuantumChromodynamics, with emphasis on results from COSY and other accelerators . This is donein the framework of phenomenological models and effective theories . These activities arefurther strengthened by a strong visitor program and numerous world-wide collaborations .The diversity of the research of the theory group is demonstrated in the corresponding chapterbelow.

COSY has the status of a "Large Scale Facility" by the European Commission within theframework "Support for Access to Research Infrastructure". Together with its partnerlaboratories, KVI Groningen and TSL Uppsala, it forms the joint organization LIFE ("LightIon Facility Europe"), which coordinates the studies with hadronic probes .

Like other institutions we have experienced and suffered from a �brain drain", mainly due tothe fact that skillfull personnel is retiring . On the other hand, we have been lucky so far sincewe were able to recruit new young scientists to supplement our staff.

In closing I would like to thank all my colleagues from within the institute and theForschungszentrum as well as the many outside users - from universities and otherinstitutions in Germany, Europe and worldwide - for their support and dedication in helpingto make COSY a worldclass facility for hadronic physics. Without the support from variouspartners, in particular from the users organization CANU and from many different fundingagencies, the successful operation of such a research facility would not have been possible .I'm also much obliged to our advisory committees for their guidelines and recommendations .Finally I thank the board of directors of the Forschungszentrum Rilich for their commitmentfor COSY and the research at our institute.

Jülich, February 2001

Hans Ströher

kA

INSTITUTE FOR NUCLEAR PHYSICS

Forschungszentrum Jülich GmbH

D-52425 Jülich, Germany

Managing director :

Prof. Dr. H . Ströher

Experimental Nuclear Physics I, director :

Prof. Dr. K. Kilian

Accelerator division, head of the :

Prof. Dr. R. Maier

Experimental Nuclear Physics II, director :

Prof. Dr. H . Ströher

Theoretical Physics, director :

Prof. Dr. J . Speth

Binary process registration in the forward scintillation hodoscope at ANKE. . . . 21

Momentum dependent efficiency of the forward Cerenkov countersat ANKE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Simulations of the inclined Cerenkov detectors for p-d separation in forwarddirection at ANKE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Methods to determine drift characteristics of the ANKE drift chambers . . . . . . . . . . . 24

Meson Production on the Neutron at ANKE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Combined Spectator and Vertex Detection at ANKE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Determination of particles momenta from TOF measurements for ANKE. . . . . . . . 27

Reconstruction of Ejectile Momenta in ANKE Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Planned measurement of the branching ratio a+ -+ 7r+q/K+K° with ANKE . . . . . . 29

Nonresonant Tr+q production in the reaction

pp->dX at p ~~b = 2.5 - 3 .8 GeV/c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

30

Production of a+ mesons in the reaction pp --> daö . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

The Polarized Internal Gas Target for ANKE - Status and FutureDevelopments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Status of the pellet-target preparation for ANKE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Test of the HAMAMATSU R5505 fine-mesh phototube in magnetic fields. . . . . 35

Deuteron Breakup pd-->pnp and Short-Range NN-Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Near-threshold co and 0 production in pp and pd collisions and polarizedintrinsic strangeness of the nucleon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Studying the co properties in pA collisions via the co -> 7r°y decay. .. . . . . . . . . . . . . . . . 38

Medium effects in the production and /7°y decay of c)-mesons in pA collisionsin the GeV region. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

ao(980) - fo(980) mixing and isospin violation in the reactions pN --> aod,pd -> ao 3He/3H and dd --> ao 4He. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41

Study of hypertriton production in the reaction pd -> 3H A K+. . . . . . . . . . . . . . . . . . . . . . . . . . 43

Studies on the Reaction pp -> ppK+K - close to Threshold at the COSY-11Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Energy dependence of the A/E° cross section ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

High statistics measurement of the pp -> pp 77 reaction at COSY-11 . . . . . . . . . . . . . . . . 46

Near Treshold Production of il' Mesons in the Proton-Proton Scattering . . . . . . . . . . 47

Phenomenological analysis of near-threshold production of g° , q, and q'mesons in proton-proton collisions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Near Threshold Production of co Mesons in the pp -> ppco Reaction. . . . . . . . . . . . . . 49

Results on rJ-Production in the Reaction pd->3He 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

A threshold Cerenkov counter for the COSY-11 facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Monitoring of the beam geometry during the measurement cycle atCOSY-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Differential Cross Sections Measurement for the p + p -> d + 7c+ Reaction at850 MeV/c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Kinematical Aspects ofMeson Production in p+d Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Charged and Neutral Pion Production in p+d Reactions in the 0 -ResonanceRegion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Investigations of Charge and Isospin Symmetry Breaking at COSY. . . . . . . . . . . . . . . . . 56

Exclusive q Production on Light Nuclei. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Measurement of Analyzing Powers and Spin Correlation Coefficients for Elasticpp Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

Results on Two-Kaon Production at MOMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

1 .2

Experiments at External Facilities

ATRAP, after half a year of operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Preparation of the Second Phase for the ATRAP-Experiment atthe AD/CERN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Monte Carlo studies for the y detector at ATRAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Measurement of the photon response ofPbW04 and CeF3 below 1 GeV. . . . . . . . . . 70

Pionic hydrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

Precision measurement of the mass of the charged pion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

2.

NUCLEAR SPECTROSCOPY

The TMR network project "Development of y -ray tracking detectors" . . . . . . . . . . . . 75

DSA lifetime measurements in'44Gd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

Investigation of the K'=8- Isomer in 132Ce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Side feeding pattern calculation near N = 82 nuclei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

On-line Digital Pulse Shape Analysis for Gamma-ray Tracking. . . . . . . . . . . . . . . . . . . . . . . . 80

Digital Algorithm for Three-Dimensional Position Sensitivity with HighResolution Ge Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

11.

Theoretical Nuclear Physics

3 .

MEDIUM AND HIGH ENERGY PHYSICS

The pion charge radius from charged pion electroproduction. . . . . . . . . . . . . . . . . . � , . . �� . 87

Neutral pion electroproduction off deuterium above threshold. . . . . . . . . . . . . . . . . .�� , . � 88

Complete one-loop analysis of the nucleon's spin polarizabilities . . . . . . . . . . . . . . . . . . . . . 89

Baryon form factors in chiral perturbation theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Low energy analysis of the nucleon electromagnetic form factors . . . . . . . . . . . . . . . . . . . . . 91

Ordinary and radiative muon capture on the proton and the induced pseudoscalarform factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Eliminating the high momentum components from realistic NN potentials . . . . . . . 94

Charge-dependent nucleon-nucleon potential from chiral effectivefield theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Three and four nucleon systems from chiral effective field theory . . . . . . . . . . . . . . . . . . . . 96

Nucleon-Nucleon Scattering in a Three-Dimensional Approach. . . . . . . . . . . . . . . . . . . . . . . . 97

Spin Configuration in the Deuteron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Pseudovector NNg Coupling in Time-Ordered Perturbation Theory. . . . . . . . . . . . . . . .99

Scaling property of the half-off-shell T matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Chiral dynamics in the presence of bound states : kaon-nucleon interactionsrevisited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Pion and kaon vector form factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

The Kg scalar form factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

J/T -* O;c7r(KK) decays, chiral dynamics and OZI violation. . . . . . . . . . . . . . . . . . . . . . . . . . 105

The strange quark mass from QCD scalar sum rules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Chiral SU(3) low energy constants from iur and aK scattering . . . . . . . . . . . . . . . . . . . . . . 107

Correlating s- and t-channel form factors by dispersion relations . . . . . . . . . . . . . . . . . . . . 108

On the Possibility of Observation of ao -fo Mixing in the pn->da o Reaction. . 109

On the origin of the short-range repulsion in the KN system . . . . . . . . . . . . . . . . . . . . . . . . . . 110

The S-wave A;r phase shift at the mass of the 2.7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

The reactions pn -4 dco and pn -> do near threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

The reaction pp --> NIK close to threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113

q -meson production in the reaction pp -> ppq . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

Pion-nucleon scattering to fourth order in chiral perturbation theory. . . . . . . . . . . . . . . 115

Pion-nucleon scattering in an effective chiral field theory with explicit spin-3/2 fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Towards an understanding of isospin violation in pion-nucleon scattering. . . . . .117

Two Pion Production on the Proton in Hadronic Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

Incoherent photoproduction of q -mesons off deuterium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Coherent dissociation ofpions into hard dijets on nuclei. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Diffractive structure function at very small 6 and unitarity corrections in thecolor dipole approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Anatomy of the differential gluon structure function of the proton from theexperimental data on F ,P (x,

QZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123

CP-odd anomalous interactions of Higgs boson in its production at photoncolliders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Generalized Mesons in Dense QCD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125

V -> YY in Dense QCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126

Instantons As Unitary Spin Maker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Casimir Interaction among Objects Immersed in a Fermionic Environment. . . .128

4 .

NUCLEAR STRUCTURE AND REACTION MECHANISM

Microscopic description of total spectra in 40Ca(a,a') at Ea = 240 MeV. . . . . . . . . 131

Coulumb Dissociation as a Tool for Nuclear Structure and Astrophysics. . . . . . . .132

Photon-Photon and Photon-Hadron Physics in Very Peripheral RelativisticHeavy Ion Collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133

Bound-Free Pair Production in Relativistic Heavy Ion Collisions . . . . . . . . . . . . . . . . . . . . 134

Pionium interacting with matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Cross-correlations in the stock market: DAX versus Dow Jones . . . . . . . . . . . . . . . . . . . . . 136

On the Electric Field of Homogeneosly Charged Ellipsoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

III.

Accelerator Devision

5 .

COOLER SYNCHROTRON COSY

Operating Report ofCOSY in 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143

7 .

SPECTROMETER BIG KARL

Polarimeters for the internal and external COSY beam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

D"-Beams from the Cyclotron JULIO for COSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Experience with a VitroPerm cavity in COSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Magnets, Alignment and New Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149

6 .

ION SOURCES AND BEAM TRANSPORT

Ion Sources at COSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Application Programs and Accelerator Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Magnetic Spectograph BIG KARL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

8.

RADIATION PROTECTION

Radiation Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..161

IV. EUROPEAN SPALLATION NEUTRON SOURCE (ESS)

9 .

TARGET PHYSICS

Spallation relevant investigations at COSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Helium production in thin targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168

Damage induced by GeV protons in window materials of spallation neutronsources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..169

Composite Particle Emission in 2.5 GeV Proton induced Reactions on Au.. . ..170

First neutrons from JESSICA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171

Development of the PISA experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Preliminary Test of the Phoswich Detectors for the PISA Experiment. . . . . . . . . . . . 173

10. ACCELERATOR COMPONENTS

System Optimisation of a Superconducting Linac for the European SpallationSource ESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177

System Design for a Superconducting Version of the ESS Linac . . . . . . . . . . . . . . . . . . . . . 180

ESS Test Cavity: First RF Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . � , .���� 182

Aspects of Tuning and Feeding a 5-Gap Spoke Resonator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

Mechanical Resonances and Microphonicss in a 5cell 500MHz SC Cavity. . . ..186

Active Compensation of Lorentz-Force Detuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . .������� , 188

Low-ß Superconducting RF Accelerating Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

High Current Beam Dynamics in an ESS SC Linac. . . . . . . . . . . . . . . . . . . . . . . .�������� , 192

Beam loss Studies for High Power Proton Drivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

V.

Technical Developments

11 .

ELECTRONICS, SEMICONDUCTOR DETECTORS

Electronics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Semiconductor Detectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

VI.

Scientific Council COSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207

VII.

Program Advisory Committee (for COSY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

VIII. Collaborations .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209

IX. Personnel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219

X. Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227

XI.

Index ofAuthors.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

I . Experimental Hadron Physics

1 . MEDIUM ENERGY PHYSICS

1 .1 Experiments at COSY

1 .2 Experiments at External Facilities

2. NUCLEAR SPECTROSCOPY

1 .1

Experiments at COSY

In december 1998 COSY extracted its first po-laxized proton beam with a beam momentum of798.0 MeV/c for the external TOF experiment .The measurement of the reaction pp --> pp'y wasdoneusing a liquid hydrogen target. The detector setupconsisted of the Rossendorf start-detector, the threelayer ring- and the three layer quirl-spectrometer .To calculate the cross-section and the analyzing-power of the reactions to be analysed the polarizationof the the beam has to be determined very precisely.This was done using two different methods:

1 . For monitoring the beam polarization online theexternal polarimeter BoPol with its own ana-lyzing reaction pC -+ pC and the correspond-ing well-known analyzing-power Ay = 0.55 wereused.

2. The polarization was calculated ofine by us-ing the asymmetry of the counting rates in thereaction pp -+ pp (analyzingpower Ay = 0.35)measured in ring-barrel coincidences .

Both methods yielded the same value of roughly 40%for the beam polarization.The first results presented here are based on the fol-lowing coincidences :

" quirl-quirl,

" quirl-ring,

" quirl-fass and

" ring-ring.

Status of the analysis of the pp -4 pp'Y reaction channel

The results of a missing-mass analysis used to re-construct a third particle in the final state areshown in figure 1. One can see that the dominat-ing reaction is pp -> pp7r

O as expected in this range0.5° < O < 26.1°.The background in both plots is seen at missing-masses up to mM = -0.018 GeV/c2. For the differ-ent spin directions of the incident beam the increaseof the background with the missing-mass shows dif-ferent slopes . Therefor two different normalizationfactors have to be used for substracting the back-ground counting rates determined from empty-targetruns.The increase ofthe background during the beamtimeis shown in figure 2. The time comsuming analysisof the normalized counting rates is still in progress .This has to be done for different cp - ranges seperately

*Inst. f. Experimental Physics I, Ruhr-Universität Bochum

A.Wilms* for the COSYTOF Collaboration

e=

Figure 1: Missing-mass contribution of the third par-ticle for the two different spin directions of the inci-dent beam. The contribution for spin up (left), forspin down (right).

34

~ 5

21

4u

42

44

A5

sa :29

M `,? . . . 34 . .M

01

4

42

44

43~ .r .RRN

bm.Pajg j

Figure 2: Analysis of the background events.

Theincrease of the background counting rates in the fulltarget runs is shown for both spin directions (spinup: left, spin down: right) .

to calculate the cp-dependent asymmetry of the in-vestigated reactions and futhermore their analyzing-powers .The dependence of the counting rates on the solidangles can be eliminated by using the so called"super-asymmetry"

NLt . NR,y'

NRT_-NL.4 =P

NLfi 7NR1 +

NRT7NL1

which relates the spin dependent counting rates atthe left-hand and right-hand side of the detector tothe polarization P and the analyzing-power Ay of thereaction.

Supported by BMBF and FZ Jülich

Ay ,

Polarization Effects in Proton-Proton Bremsstrahlung

E. Kuhlmann* for the COSY-TOF Collaboration

Early in 1999 the first polarized proton beam ex-tracted from the COSY-ring was delivered towardsthe COSY-TOF spectrometer for a study of the ppy-reaction at Abeam=798 MeV/c. The spectrometersetup consisted of Rossendorf start-detector and 3-layer endcap (quirl and ring) as well as 1-layer barrelas stop-detector . Charged particles were detectedin the angular range 19= 2°-70° originating mainlyfrom pp-elastic scattering . The standard 4mm LH2-target was used, as were several veto detectors in or-der to define a small beam spot . The average beamcurrent was 5* 105 s-1 , the beam-polarization around45%. The analysis is still in progress ; here resultsdeduced for the ppy-reaction from barrel-barrel co-incidences only will be presented. For this subsamplethe expected photon energy ranges from zero to 150MeV or roughly 75% of the maximum possible . Foreach ppy-event identified by means of the methodof missing-mass analysis a set of three 4-vectors waswritten on disk which then could be used for fur-ther analysis . Unwanted background events are elim-inated by subtraction of a suitably normalized set ofempty-target runs taken at repeated intervals duringthe experiment, those from secondary elastics are es-timated to not contribute more than 10%.Splitting up the bremsstrahlung events according

to the polarization of the beam (t or ~) and the4~-direction of the photon (left/right and top/bot-tom denoted as 1/r and t/b) background-correctedmissing-mass spectra are obtained as shown in Fig. 1.Due to the 4b-symmetry of the setup, events from"spin up" (T) and the photon going to the left canbe put together with those from "spin down" (~)and the photon going to the right. The same con-sideration holds for the pairs l~+rf as well as tf+b~and t~+bf. Defining spin-dependent yields NT (N~)= lT+r~ (1~+rf), respectively, and likewise for thetop/bottom-pair, one can deduce two asymmetriesA=(NT-N1)/(NT+Ny) which amount to A=0.2 forthe left-right and 0 .0 for the top-bottom pair . Inview of the moderate polarization of the beam whichwas available in this very first run sizeable polariza-tion effects seem to be present in the ppy-reaction .As a byproduct a sensitive dependence of the rate

in accumulated quasielastic pX-yield for differentempty-target conditions was found (Fig.2) with Xdenoting any material present in or on the foils ase.g ., H2, N2, 02 or C . Three distinct regions are ob-served which are from left to right: cell filled with

*Inst. für Kern- und Teilchenphysik, Technische UniversitätDresden; supported by BMBF and FZ Jülich .

gaseous H2 and foils still covered with condensates,foils cleaned through local heating and cell evacu-ated, foils cleaned and cell filled with gaseous 112 .Especially the latter increase in yield is an encourag-ing result for future experiments relying on spectatortagging where gaseous targets are mandatory in or-der not to absorb the low-energy particles .

".3äCöU

wN

0vb

T

so706050403020100

807060504030201o0

,-, 200

r- 180

160

140

E

-0.01 0

tT+bi

120

100

80

60

40

20

00 2.5

-0.01 0missing masse /(GeV/c2)2

Fig. 1: Missing mass spectra as deduced for variousprotonspin and reconstructed photon flight directions .

eee

pX_quasielastic

e

e

*

dirty falls, with gas

*

clean lolls, no gas

*

Clean fails, with gas

1 .1-1 .1-1 1 . 1 .1 .

.I .

I . . . .5 7.5 10 12.5 15 17 .5 20 22.5 25

Spill-Number (* 100)Fig. 2: Spill-integrated quasi-elastic yield as obtained fordifferent empty-target conditions .

so7060 1l+rT5040302010

0.01 "-0.01 0 0.01

807060 U+bT50403020100 av, f . b,7,=,

0.01 -0 .01 0 0.01

The COSY-TOF Collaboration, Experiment E7 (Spokesperson W. Eyrich)

As already discussed in former annual reports the COSY-TOF spectrometer is well suited to study hyperonproduction in elementary nucleon nucleon scatteringprocesses in a clean way by reconstructing the delayedhyperon decay. The highly granulated detector systemcovers almost the full phase space of these reactions fromthreshold up to the COSY limit .Differential distributions as well as total cross sections andthe A-polarization can be measured .In the meantime the pp -> K+Ap reaction was investigatedat several beam momenta between 2.5 GeV/c and 3.2GeV/c. From the Dalitz plots of these data there isespecially clear evidence on the p A-final state interactionand also indication for the influence of N*-resonancescoupling to the KA-system [1] . As shown in Figure 1 the A-polarization data at 2.75 GeV/c and 2.85 GeV/c show atrend to negative values with increasing transversal A-momentum .

a'' 1r--

Monte-Carlo+ Data 2.75 GeV/c

I

I0.1 0.2 0.3 0.4 0.5

PT(A)[GeV/c]

F+ Data 2.85 GeV/cnorm.

I

'0~. .. .. ... .. .. .+ .. . .. ... .+.. .. .. .. .+. .. . .. .. .. ..... ... .. .. .

.. .. . . ... .. . ... .. ..

... .. .. .. . .... ... .. ..... .. . .. .. ..: .. .. .. ... .. .. .. .. ... .. .`

F

1

~10 0.1 0.2 0.3 0.4 0.5

PT(A)[GeV/c]

Figure 1 : A-polarization as a function of transverse A-momentum for beam momenta of2.75 (top) and 2.85 GeV/c(bottom)

Using the energy loss information of the various detectorsystems, the non magnetic TOF-detector also allows toseparate the reaction pp -> K+E°p from the A-production.This is demonstrated in Figure 2, where by use of theenergy loss information of the inner detector system thedominating A-missing mass peak is strongly reduced to asmall background (shaded area) allowing to separate the Z°-events in a sufficient way to extract the E° / A cross sectionratio .Besides the production ofthe neutral A and E° hyperons theTOF detector also allows to investigate the E+ production inthe channels pp -> K°E+p and pp -+ K+E+n . Figure 3 showsan event of the channel pp -+ K°E+p, which is identified by

Hyperon Production at COSY-TOF*

the delayed E+ and K° decays. For the beam momentum at2.85 GeV/c about 200 events of this type could beextracted, allowing for the first time to evaluate the totalcross section of this reaction channel in the COSY range .The K°E+p / K+Ap cross section ratio was extracted to apreliminary value ofabout 0.3 ± 0.05 .

0 r I

i

1

0.4 0.6 0.8

Figure 2 : E° missing mass distribution at Abeam= 2.85 GeV/cand background of A-events (shaded area)

With the upgraded TOF detector completed by ring andbarrel sections in 2000 a precision study of the hyperonproduction was performed at beam momenta of 2.95 GeV/cand 3.2 GeV/c . From this about fifty thousand fullyreconstructed A-events and a few thousand E-events areexpected. Moreover, the hyperon production in neutronproton scattering was successfully tested using a deuteriumtarget. In the future the measurements will include apolarized beam and in a further step also a polarized target.

References

*supported by BMBF and FZ Jiilich

(1] R. Bilger et al ., Phys . Lett . B 420 (1998) 217 .

1.2 1.4

m[GeV/cz]

Figure 3 : Hit pattern in fisheye projection of a K°E+p-eventshowing a characteristic E+ kink and a K° decay sequence

The associated strangeness production in thechannel pp -4 pK+A has been measured at a rangeof excess energies between 55 MeV and 284 MeVat the external time-of-flight spectrometer COSY-TOF. The delayed weak decay of the hyperon is avery distinct signature which allows for an efficientonline trigger and a nearly background free eventsample after offline analysis of the data . The eventsare reconstructed kinematically complete includingthe delayed weak decay of the hyperon A -3 per-, akinematical fit ensures physically consistent data .Due to the large phase space acceptance correctionsremain small and differential observables can be ex-tracted directly. Results presented here are takenfrom a recently completed data analysis [1] whichextends previously published data by the COSY-TOF collaboration [2].

.O

c0NNOV

20

18

16

14

12

10

a6

4

2

Recent Results on Lambda-Production at COSY-TOF 1

D. Hesselbarth for the COSY-TOF Collaboration

W

..

.y,o l 'ia l

F . . .

I . . . ' I . . .I . . .I . . .I . . .

I .I20 40 60 80 100 120 140 160

excess energy [MeV]

Fig.1 : Total cross section v of pp --+ pK+A from thiswork (0) compared to measurements from COSY-11(0 [3]; A [4]), TOF [2] (/) and [5] (*); the function isa simple phase space parametrisation o oc e2Figure 1 shows the total cross section of the reac-tion pp -4 pK+A for various excess energies . Oneof the two new data points (open squares) at e =115 MeV fits smoothly to the published data andfollows roughly a simple phase space parametrisa-tion . The second point at e = 85 MeV escapes thissmooth behaviour . Its value almost coincides witha measurement at COSY-11 at nearly the same ex-cess energy [4] . This behaviour might be a hint ofa cusp effect since the two points lie very close tothe Eo threshold at e = 77 MeV.In Figure 2 the angular distribution of the normal ofthe plane, which is defined by the CMS momenta ofthe three ejectile particles in pp -> pK+A, is exam-ined . Drawn is the cosine of the angle rs* betweenthis normal and the beam direction . It shows astrong enhancement at cos(rs*) = 0, i.e . the CMSejectile plane contains preferrably the beam-targetdirection. This behaviour gets more pronounced asthe available energy increases . The strong devia-tion of this observable from (flat) phase space as

'supported by BMBF and FZ Jülich

well as from other channels measured at TOF (seepp -3 pprl, S . Marwinski in this report) and its clearscaling with excess energy might have implicationson the mechanism of associated strangeness pro-duction.Nc.d

Nr'c3.ö

C.ccc

0 .5

0

0.5

0

0.5

E = 85 MeV

£ = 115 MeV

E=171MeV

0-1

-0.5

0

0.5

1cos(x*)

Fig.2 : Three particle ejectile plane distribution for dif-ferent excess energies e: as e increases (top -I' bottom),the anisotropy becomes more pronounced .

References[1] D. Hesselbarth, PhD Thesis, submitted to the

University of Bonn (2000)[2] R. Bilger et al ., Phys . Lett . B 420 (1998) 217[3] J. Balewski et al ., Phys . Lett . B 420 (1998) 211[4] S . Sewerin, PhD Thesis, Univ. of Bonn (1998)[5] W. J. Fickinger et al., Phys . Rev. 125 (1962) 2082

71-meson production at COSY-TOF*

S . Marwinski for the COSY-TOF Collaboration

In February 1999 the 77-meson productionin proton-proton collisions was measured at theCOSY-TOF-spectrometer. The data were takenwith the large TOF version consisting of Quirl,Ring, Barrel and Rossendorf start-counter at ex-cess energies of 15 MeV and 40 MeV [1].The calibration of the detector was done with copla-nar two hit events, pp -+ PPetast and pp -+ da+ .The time resolution of the detector is better than300 ps . For the lower energy the missing-mass-analysis shows a small 77-peak with a resolution ofo, = 0.6%. Only the data of 18500 71-events withneutral decays at 15 MeV are shown .After correction of the acceptance the angular dis-tributions of all ejectiles of the reaction with respectto the beam direction are flat at 15 MeV excess en-ergy. This suggests pure s-wave scattering .In the center-of-mass system the ejectils of a threebody reaction are in a plane, the ejectilplane . Thedistribution of the angles between the beam vectorand the normal vector of that ejectilplane is shownin Fig. l. Also this results in a flat distribution. Thedata are taken from a missing mass cut: m,, ±0.1% .

ii.. . .._ .... . . t.. . . _... ... . .t... . .... ....

... . ..... ...i_._ . ..... . .... ... . ....

1

I

:

... ...... .. . . ..._... . . ..~. . ...._... . ..i. . . ... ..... . .

1.... . ._. ....3 ... ...... ....' ..... . ._.. ..L.. . .... . . ... .~ ... . .... .

I

1

i

I

i

I

i

i

Fig.l : Normal vector distribution of the ejec-tilplane . The normal vector is calculated by the vectorproduct of the two proton momenta in the center-of-mass system . The proton with the higher energy istaken first. The data are normalized to the total crosssection : at = (2.11 d_ 0.32)pb [2].Fig.2a shows the Dalitzplot for the reaction pp -4pprl at 15 MeV excess energy with kinematically fit-ted data . The dalitzplot shows a strong final stateinteraction between the protons which is seen inFig.2b, the projection of the dalitzplot (solid line)on the pp-axis. The dashed line describes in com-parison the phase space distribution . On the otherhand a final state interaction between a proton andthe 77 is not seen in Fig. 2a .

.� 2 .28w

d~2 .27

2 .26

2 .25

2 .24

2 .23

2 .22

2 .21

2.2

2 .19

2.183.5 3.'51 3.52 3.53 3.54 3.55 3.56 3 .5, 3 .58 3.L59 3.6

W(PP) GeVi/e

Fig.2a: Dalitzplot Fitted data with cut in X2 < 0.5 .

Fig.2b: Projection on Proton Proton SquaredInvariant Mass. Measured results (solid line) in com-parison with the phase space distribution (dashed line) .The distribution of the measured data including theFSI follows the calculation of [3].* supported by BMBF and FZ Jülich

References

[1] S . Marwinski : 77 Meson Production at COSY-TOF, Annual Report 1999, IKP, FZ Jülich

[2] H.Calen, U. Schuberth et al ., Phys . Lett . B 366(1996) 39

[3] H. Calen et al ., Phys . Lett . B 458 (1999) 190

~ II I I 1 1 I I

TI1 I

.I 1 I 1 I I II I I I I

I I I I 1 I II 1 I I 1 1I I I I 1

1 1I 1 I 1 1

1 1

-------------------------I II II II 1

0.80.8

I I 1 I I 1 1I I I I I 1 II 1 1 I I 1 II I 1 I . 1 II I I I ^.~

~I~1 1 l ".1 __ I-

I 1I 1I I1 I1 I

i 1 II II I I ~' i i " .I 1 I rl 1 I II 1 I I I 1, . 1

1 I1 I

I 1 I~' " ~~ I LI I I0.6 I 1 li I I I

I 1 M I I~--_- I II~ I I

I 1 ~ 1 1 I II 1 ; I I I I I

I; I 1; I 1

I I I I I I I

I 1 I I I I I

L

1

L I 1I 1 r_- I___- I I I

I I 1 I 1 1 1I 1 I I 1 I II I I 1 1 I 11 1 ~ I I 1 I 1

. 1 I

1 11 I1 I1 I

1 I I I I 1 I I

1 I I I I i I1 I ~ I I I

!I

I I . I 1 I I 1I I ; 1 I I I 1

I

! I I

1 I 1I II 1I I

0 3.5 3 .81 3.52 3.83 3.54 3.55 3 .56 3.57 3 .58 3 .59 3 .6

WOW G-V/c'

Status of the development of a new data base for COSY-TOFusing the object oriented data analysis framework ROOT

C. L. Plettner*, K:Th. Brinkmann*, H. Freiesleben*, L. Karsch*, M. Schulte-Wissermann*for the COSY-TOF-Collaboration

ROOT [Ram], the successor of the FORTRAN baseddata analysis package PAW is an object-oriented ap-proach to the analysis of experimental data in particlephysics. It provides all functionality to handle and anal-yse large amounts of experimental data in an efficientway within one framework. The class design of ROOTalso encourages the jointeffort of software developmentin alarger team.

The conventional way of storing experimental dataof COSY-TOF uses a linear structure whose length isdefined by the total number of detector channels . How-ever, considering the modular structure of the COSY-TOP detector together with the fact that for aphysicalevent the number of active channels in comparison tothe total channel number is rather small, the advan-tages of the implementation of an object oriented database are obvious: For each subdetector system an inde-pendent software module - shared library - containingthe corresponding detector class can be designed. Inthese libraries, C++ classes as data containers are de-fined for QDC and TDC values together with the chan-nel number . In this way, the data base, which is called.a Tree within ROOT, reflects the modular character ofthe complete detector : for one event only active chan-nels sorted by the subdetector contribute to the database .

Figure 1: General concept of the data flow

In Fig. 1 the general concept of the data flow issketched. Starting from existing XD data files - XDbeing the precessor of the current analysis software atTOF -the raw TDC and QDC values are copied by theprogram xd2root into new ROOT files containing theTree TRAW. In a second step the raw data are walk cor-rected and the TDC binning factors are applied. Also,for the endcap detectors Quirl and Ring the pixel re-construction is performed andthe result is stored in the

ROOT Tree structure called TLST . Thefurther calibra-tion is performed by subroutines using the TLST data .The subroutines themselves are collected in shared li-braries.

For organization of the calibration data a separateclass, TofCal, was designed. This class provides func-tions to store and retrieve geometrical informations likedetector positions, beam time oriented informations likewalk corrections, and run number oriented informationslike TDC offsets within a single file.

Using the function Apply0ff set the calibration datais applied to TLST data . In a new file containing theTree TCAL each event is stored in a structure containingthe velocities and the emission angles o£ each single hitin the detector . Thephysical interpretion of data startsfrom here .

Fig. 2 serves as an example for the status of the dataanalysis for the pd @797MeV/cbeam time in Decembre1998. Here, the particle velocity ß = v/c is plottedversus the emission angle 91ab for two-particle events inthe barrel detector [Boe00] . 80% of the.available datawas used for this plot . Two sharp bands of protons

pd @ 797 MeV/c

Figure 2: Plot of (3 vs . 91ab for the pdelasti, Q 797MeV/cbeamtime.

and deuterons from elastic pd scattering can clearly beseparated from the broader band which is due to thedeuteron break-up.

References[Rad98] F. Rademakers, Ren6 Brun, Linux Journal, Is-

sue 51, July 1998[Boe00] COSY-TOP collaboration, A. Böhm et al .,

NIM A433(2000), 238* Institut für Kern- und Teilchenphysik, Technische Univer-sität DresdenSupported by BMBF and FZ Jülich

investigation of the mechanical beltac=ior of theicron BC408 plastic scintillator material due to heat

treatment were continued and finished . A slab of

100(i x i(X) x 1() mrn' which was heated totemperature which is needed for bending, was foundto shrink ,G, .2 - 2,

a* in length and width, while, theess iacrc:.ased by 4,8tt . These changes have to

nt for the layout of the scintillatorstrips, for the bending fixture, and for the lightguides .

Im long strips were bent in first testswithout damaging the scintiliator surface . Cosmic raytest are prepared to compare the photon yield of thescint llator before and after being bent . Special timediagrams for the heating of the oven have been

-clt pod for to take into account the heat capacityof' the bending fixture . Investigations to find out theoptimal scinfllator thickness for the outer layer ofthe three layers have been pertonned with cosmicrays . 4m long and 1(Xhnm wide scintillator strip-,with a thickness of Smm, t(}mm . l5tint) . '(hour and

respectively were e artairted. The: cross)ns of the, l timm, 2()tnrn and 2-tent wide strips

are larger than the cross section of the _' inc'phototnultiplier tube A'P2(f2()}, set it has tomatched by a ramp at the light hunt? . Williincreasing thickness of the scintillatot the lightproduction by charged particles increases, but theinisnaa(ch it) the PRAT leads ice a loss of light . With

I'ttum thick scintill-11tu 'Mr) a optutnrttt wastxrnd .

calorimeter

)Itcnts or oh,- ,cnrral scinttIlator Calorimeter, :(l and a ", cltthlecl in '(it)t)" +4 hexagonalintllalors are stacked inside a supporft

ne fs . F'IL . I), Thc, caloritnet r is operated itt the°f01 , vacutatr tatrk, the light is fed out throughhglnguides it) the cadflangc (s, Figs . ',3) . .Aralibrattott ~ -,, ,icn, consisting of' blue light enutlim ,thcxfes ha, 1 ccn ctcVel0l:VA and succcssfulIN fcsted atthe Univcisitr ctt 'l iibIngcn . A,

first bean) tirnc wasto calibrate tltc caloritneter ni (xlules ti+-ith the

reaction pp clastic and III) .....> d 7z,and pp

tinic of flight sprctrorneter

~et up with adisuanec of the endplate; to thc target of one Inetcr .thc bcani inornerttum wits 1454 Nlc\Vc,l c,am times with it nionicinum of I4faised to C\ ;irtttiir the reactionanalvratitsil (it thc ciata is still III Ino2ress .

stiaar tu~ h. :~m~sttysit:,'7~ntr!,it A"t

. Erhar t~, D . Filges', h'1 . Fleischcr2, U. Jd

e `, H. H

ek', G. Hansen2,ein', K. Kilian *, I. Kreßt, C . Meixnert, S. Me=l', l%d . Paul', W. Renftle",

E. Rcxierburg ` , l1 . Stechernesser`for the COSY-TC)F= Collaboratic,a

D. Filges, R. Geyer, K. Kilian, V . Kozlov,1 . Mohos, R. Nellen, K. Nünighoff, S . Orfanitski, P . Wintz

Up to now 300 single straw tubes were produced and toolsfor mass production of straws were developed. Thecharacteristic wire tension of all straws showed only slightvariation within +2.54g and -1 .68g at 40g.

An overpressure inside the straw around 1 bar was neededfor sufficient tube straightness. Stability of a straw packagewas reached by gluing single straws together in double-layers of2x16 elements .Single tubes showed characteristic torsion depending on thechosen overpressure (torsion angle of 7 deg at overpressureof 1 bar). This effect requires gluing points only in thestraw mid-section so that both ends of the tubes are free torotate under the action oftorsion momentum .For electric ground contact of the straw cathode foilscylindrical springs made of Cu/Be were developed . Thesprings allow for lengthening and torsion of the straw tubesunder pressure.A prototype detector (Fig.1) consisting of 128 strawsarranged in 4 double-layers has been build to study strawcharacteristics such as efficiency and spatial resolution withcosmic ray tracks . Later this setup will be used for high-resolution measurements of the light-weight straw trackerfor TOF .

All parts ofthe final electronic readout have been fixed andwill be developed by the �IKP Elektronik-Werkstatt" andthe ,Zentrallabor fuer Elektronik (ZEL)". Small (6 x 40mm2) boards combine high voltage supply and signal linecontaining HV supply resistor, blocking capacitor and thepreamplifier layout. The boards are directly connected toeach straw. Fig.2 shows first preamplified straw signalsproduced by a 55Fe radioactive source .

Thin grounded coaxial cables connect the preamplifiedsignals with ASD8-B chips [1] for further signalamplification, shaping and discrimination . Digitisation ofthe signal times is done by Fl-chips [2] . A new dataacquisition system for the readout will be developed byZEL .

Status Report of the Straw Tracker for TOF

Fig. 1 . Prototype detector consisting of 4 double layers ofstraws .

TÜVWM 2.4(1{:SlS

145 AMS

References:

L'.ü°

2.5.0m;

. m

24 Duc2000

17 :57:91

Fig_2. Straw tube signals of a 55Fe radioactive source .

[1 ] M.Newcomer et al ., University ofPennsylvania, Pa,USA.

[2] G.Braun et al ., Universitaet Freiburg, Germany.

u~c?uld ~ ~-lachi

assisted 32crrr lc~rtg heat pig swstlra.5 I?een develo esd when.= ~e target

used as transpt~rt medium. recently- ,tang heat pipe was d3e~re crl?ed fc~r future

Time c~f I°`light ~ trt?mt~terit w°vr ~ safely with a c~~eight crf

than 6i)ß fcar the heat pipes-targetA ?rn Ictnl; ccappc'r hc.~at et>nductc-~r caf

peter we ld

a~~e a weight tafuId tt ce r are than

I () hot.trs toand the temperature difi'erc ncect~ld encl and the target

I?resentlr~~ used ccu~~litc?t prc~z~ide the necc.' "ar

temperat~rre~. The cc?mhinatic~n chi a Icing heatI~i c, acrd a tttin t~zrgclt cell prcwides e~tellentuc~rking cr~nditic~nc with minimum densit~~vttriatic~n in the target at ~t temperaturediI`fti~rence c?~~tr rule mc~tc.~rs c?I' less thantf~'igure l } . L.üluid hyiirc Ken L,Hr iti the

gettztatc.~rial and thc' heat transport medium. Tlrc~teixtperature at thc' second stagy c?t thi' cc}Id

tn> cill tt c~n in 'I` t cc>mesccx~Iin :̀; maclrirrc: rr%?tst~~sterrr . l'1`t11Z1 higtirc~

;tic'ies c~f thc:'- hetrt I? I?c'

~ec's a.ls+~ tlrat the.~n~pcrature at the t>ut r suriacc .~ t~t tlre ta

l T> i~ stahl~' at I~ .'~}f~K . 'Thc' i.'i ~~l tltlu`nfc}r thc' ?m long hi.=at l,ipe is ahc~ut

I7f.~trrs .

I'1'c~cc~c~IÜrg

thc:

s~~stettl

uith

Iiclti}gc~ir cc~tllil rc::di.i~:c~ that tirrre . Tltis

'~,teiri wati al~ c~ tis~'d u=ithc~ut pr~?hlc'n1s wlt(~`,IIa rtn f 'V~

f~~ r cic~titec~ ut~r it nec.~ds s+,mt'~Ic~~~e~lc~i}rrrc~trtw duc' t~} thc~ stnall I?rt~ssui~t rar~r[rcl

tllt'1'l'1 't)1"t'IC`tr1[~t'rättirc'

i' 1t1gL'

tf~r

Iiriui~r . TIr~" etAf~ctiti°c, thexrrnal 4c}ntlucti~tityr

ttt Ir~,~cir~~gc~tr heot hi l c, s~~ te1a1 is ~{~~~'~`lc'rtr .i~, u~Irich in cc}irr~?~triwc~rt u-ith thcttrt~rctt~tl ~'c~iltlti~a ~~it1~ c~t ~.t 'tYt I~,ng rc~hlx>r

c:Y~Iintlci~

t~ �=1~

Vy'tcnr .l~~i

is

i~,~

tii~lesI>cttk~r . "fE~e Iriglt thcriTral rc~rrdticti~~it.~' c~f' tlte

heat pig stabilizes the target tem rawithin ~O.ß

in the wcar in,g rarr e c.f liquidhydre~~en, The theme conductivity withmethane

thermal c+anductivity

(~e~Icon is that the heat

ttc'r'currrpareci tt~ metallic

conduetctrs .

1 f'tr~~tt~gra~ti~nditi~~n~ ~?t' ?ir't ic~ng h~,r3rt~ ~n h~~a pil~"-t.rr

c~ell

~~c~rtrhinatic n,

~.I.t:1~S,-t~s

}~.

T~

=I

.

l;eierenre:s :1'j S . 1bit<~I-S<~trlact ~t aI<, f`

w L ~tit>~rrleni~ i ¬r( . .' {1~~' t-rt°c}gtnir `fi,tr~c't ~~~t~ r~" T1~I-> .~'~trr~ .

1 ~1. . t~ r~hri "E~tat (}i.I~ ~~ietl~.'~ :in~ .i t~:c;Irrr~~4

dc~ne. This is uscf l fczr;~irin~ ~ Lhe et~mpon ntin~; laser a

'>t~;rrz,

the usertem compane.rtts

monitor . The safetyinstalled. This mane

"

sefu for makingsvstez

~rksoperati¬~rt. :Ewithert

cc~m~t~ter crr

w

t ti~ ec~mesystem tc~ th~

smallvacuum systern ttt stm la.e t i' T(}l-~arra

ernent. IC c~n zsts c~f a t :t~a l?um~, tw~hanical

p~ ps,

twc~

t~ae~surements ic~r ttte hi

vacu rt7 t~d t~tvurn. two

valve. The s

tem was testedmc~d:~es . The test results shc~tiv L srt

what it shoind, hri a gtxxlstahle transitir~r~ frc>m the

~d~.' tind vicevei`~a . Also the issalaticttt c~ t e %am line area.cceed cl withrtutw

~t~lems. ~i~urers a r~n in~~ screen with ~e ~cht~matic

dia~ratxt +~f ~e Tt )1? vaet~um s~~stt~m andindications ctf the Matw ~ a e~ments andvaeuum valu~'s .

l~+eter~r~ces :

c~n l n~~ st~r~n 1`c>r tltc~ ~t~l~t~cn t ica~ram c>t the ' '{ ll° vactrutrl svst~.:rr~,

~~c~~ t~ntt()

t ~

Sc~ttware~ ' ~ftitf~rtl ~c ;ltwarit} 17r~~~r~frzl ci~ssi~rt » 1~~<I(.~ .

The ANKE experimental program on K+-meson pro-duction in pA collisions has been continued during atwo-week beam time in February 2000 . For the mea-surements adedicated detection system at the side ofthe spectrometer dipole D2 (see Fig. 1) optimized forthe identifcation of kaons in an up to 10 6 times moreintense background has been used . Data taken withcarbon, copper and gold targets at beam energiesT = 1 .0,1 .2,1.5,1.8, 2.0, 2.2 and 2.3 GeV arenow be-ing analyzed [1, 2] . Double-differential cross sectionsd2a/dQdp for K+-production under forward angles19 _< 12° in the momentum range pK+ ;~,- 170 . . .510MeV/c could be determined even at beam energiesfar below the free NN-threshold (T = 1.58 GeV) .As a first unexpected result, the target-mass depen-dence of the cross sections scales roughly like A2/ 3 ,

both at T = 1.0 and 2.3 GeV.D2

tm

TOF"slart

MWPC1,2

MWDC 1.3

\hodooslator

scops

M. Bfischer for the ANKE collaboration

Negative ejectles

Telescopes with (TOF-stop, AE,.. .)

Positive ejectiles

Figure 1: Floor plan of ANKE.

Status report ANKE*

During a second beam time in Sept. 2000, ANKEhas been equipped with target-near semiconductorcounters for spectator-proton detection [3] . Usingdeuterium as target material in a clusterjet target,this technique allows one to define reactions of theCOSY-beam protons on neutron targets. The datafrom the first test beam time show that events fromelastic proton-neutron scattering (pn --+ pn) as wellas from 7ro-production (pn -+ pn7rO) can be identi-fied . In both cases, the fast ejectile, p or d, emittedin coincidence with the spectator proton is detectedin the ANKE forward detectors [4, 5] (see Fig. 1,located close to the beam pipe between D2 and D3).Data from previous beam times on the reactionspp --} d7r+/pn?r+) have been analyzed [6, 7] with thegoal to determine the spin-singlet/triplet ratio atTbeam = 500 MeV. It turned out that the singletcontribution is at most a few percent at this beamenergy.The experimental program with ANKE in 2001 willfocus on the following topics : "Investigation of thenature of ao(980)-mesons in the reaction pp -+ dao+[8, 9, 10] . Themeasurements foresee to determine the

production cross section for this meson in pp colli-sions and to observe_the two decay channels of theao-meson, a0 ~ K+K°/-7r+77, in order to shed lighton the structure of the resonance. The experimen-tal program has been intensively discussed duringa workshop held at ITEP/Moscow on July 13/14,2000 [11] . *Measurement of the deuteron breakupinvolving large momentum transfers in the reactionpd -+ ppn [12] . In a first beam time in Febr . 2001, itis planned to measure the spin-averaged cross sec-tions at various beam energies in the range T =500 . . .2000 MeV. *Measurement of w- [3] and 7r°77-production [13] in pn interactions .Two new targets are currently in preparation forANKE: a polarized target [14], to be operated witha storage-cell, and a frozen-pellet target [15] . Theformer will allow to use polarized hydrogen and deu-terium as target material . During first tests of theatomic beam source, target densities comparable tobest values published for other sources could beachieved . The pellet target has been transfered fromITEP/Moscow to IKP and, as result of several testruns in 2000, first production of droplets from liquidhydrogen has been accomplished.Further technical developments for ANKE are:.installation of a detection system for negativelycharged particles, in particular K--mesons [16], seeFig. 1; .extension of the target-near detection systemin order to allow for vertex reconstruction ofejectilesemitted from an extended storage-cell target [17] and"design studies and tests of a photon detector madefrom PbW04 to be installed around the target regionof ANKE.References :[1] M. Bfischer, H. Junghans et al ., contr. to this

131415161718

report .Chr.. Schneider et al ., contr. to this report .I. Lehmann et al., contr. to this report .V. Komarov et al., contr. to this report .M. Bfischer, S. Dymov, A. Kacharava et al .,contr. to this report.

[6] M. Bfischer, S. Dymov et al ., contr. to this re-port .

[7

A. Khoukaz et al ., contr. to this report .

`[8

V. Kleber et al., contr. to this report .9

V.Yu. Grishina et al ., contr. to this report .1

H. Müller et al., contr. to this report .111 Proc . Workshop on as physics with ANKE,

Berichte des FZ-Jülich 3801, ISSN 0944-29522000), M. Büscher and V. Kleber (editors) .

[12] T. Komarov and Yu. Uzikov, contr. to this re-port .A. Khoukaz et a1., COSY proposal #94, (2000) .R. Emmerich et al ., contr. to this report .V. Balanutsa et al., contr. to this report .H.R . Koch et al ., IKP annual report 1999, p.28.R. Schleichert et al ., contr. to this report.V. Hejny et al., contr. to this report .

*Work partially supported by BMBF, DFG, INTASand RFFI.

First Results on the Subthreshold K+ Meson Production at ANKE*

M. Biischer, H. Jungfans, V . Kopteva, M. Nekipelovb , K. Sfstemich, H. Ströher

The magnetic spectrometer ANKE (Fig.l) has beeninstalled in the COSY-ring in May 1998 . One pri-mary goal was to investigate K+-meson productionin proton-nucleus interactions close to and far belowthe free nucleon-nucleon threshold at 1.58 GeV.

Figure 1: Top view of the ANKE spectrometer .Measurements of inclusive kaon momentum spectrain the forward direction for C, Cu, Au targets havebeen performed in a proton energy range 1 .0=2.3GeV. Ejectiles, leaving the strip target with angles-12° < O < +12° and momenta in the range110+525 MeV/c are bent by the dipole D2 to thedetection system comprising 23 start counters (TOFstart), multiwire proportional chambers (MWPC 1and 2) and 15 range telescopes along the focal sur-face of D2(Fig .2) . K+-mesons were selected from a

Stop

AE

Cerenkov

Degraderl

Degrader IIVeto

p+ n,

Figure 2: The sketch of the telescope in K+ detectionsystem .

huge background of mostly pions and protons by us-ing time-of-flight and energy-loss criteria in start andstop counters, a reconstruction of the trajectories ofejectiles, by exploiting the range differences of theparticles hitting individual telescopes and by detect-ing delayed muons or pions from the decaying kaonsstopped in front of the veto counters .The detailed description of ANKE-spectrometer andof the K+-identification can be found in refs . [l, 2] .The complete analysis of all the data is still inprogress . Here we present first results of the cross-section ratios for different targets and the values ofthe absolute cross sections obtained at the lowestproton energy of 1.0 GeV.The double differential cross sections for K+ produc-

tion in pC collisions with momentum PK were ob-tained from the number of kaons NC identified ineach telescope (i) relative to the number of pions de-tected by the stop counters NC of the correspondingtelescope. The ratio of counts was corrected by thedetection efficiencies e and normalized to the corre-sponding proton beam fluxes Mc andMK and to thecross sections of it+-meson production in pC inter-actions in forward direction at 1.0 GeV known fromthe literature [3, 4, 5] . Thus, the cross section is givenby:

where EKl(i) is the intrinsic efficiency of the telescope(i) (corresponding to a certain momentum range),which takes into account the geometry and the de-tection probability of the decay muons and pions de-layed by at least 2 .5 ns in the veto counter with re-spect to the signals from the stopped kaons. edt(i)is the efficiency with which the kaons reaching thedetectors are observed .>,0.4ä'E3 0.3

Wc, 0.2ö4 0.1

E" 0

d2 o'C _ d2U,, (NC)tel(f) MC 1

dQdp_

dQdp (NC)sv(i) MC ex x x xetel(i) ' edet(i)

eMWPC(i)

edecaye=edet(i) ' EMWPC(i) ' deecay

y 0.8

= 0.60

20.4A

5 10 15

5 10 15Telescope number

Telescope numberFigure 3: Telescope efficiency eKl(i) and kwon detec-tion efficiency ed t(i) as a function of the telescopenumber .

The eKl(i) were measured at 2.3 GeV (where the K+yield is rather high) as ratio between kaons detectedby the proper start-stop combination and kaons de-tected by the telescope in coincidence with the samestart counters (Fig.3) . The start-stop measurementswere done with low energy-loss thresholds in thestart, stop, DE - counters and wide TOF-gates toprovide the kaon detection efficiency eet(i) to be notless than 0.98. At 1 .0 GeV the kaon data analysiswas done with the higher thresholds and narrowerTOF-gates in order to reduce the several orders ofmagnitude larger background which is present in thiscase . The kwon detection efficiency was reduced toedt(i) = 0.4-0.8 as was checked with measurementsat 2.3 GeV, whereanalyses were performed with wideand narrow gates(Fig.3)The pion detection efficiencies edet(i) on the averagewere equal to 0.98. MWPC efficiencies CK

MMWPC were equal to 0.970.99 . The decay rates

between the target and the stop counters were de-termined as ed0ay = (0.30 _ 0.36) for kaons andedecay = (0.85 =- 0.88) for pions. Relative monitor-ing of the proton beam interacting with the targetfor different energies and nuclei (A) (MÄ and MÄ)was done with an accuracy of 2.0% using 4-fold co-incidences of telescopes 2, 3, 4 and 5 (selection ofejectiles by-passing the spectrometer dipole D2) .The double differential cross sections of K+ produc-tion in pC interactions at the energy of 1.0 GeV arepresented in Fig.4 . It shows that ANKE allows tomeasure the complete kaon spectra in forward direc-tion for deep-subthreshold processes with cross sec-tions as low as 10-34cm 2 during several days of workat COSY. The analysis of data at other energies (1.2GeV, 1.5 GeV, 2.0 GeV and 2.3 GeV) is in progress .Model calculations have been started. Final conclu-sions about the mechanism of the subthreshold kaonproduction are expected to be possible after the anal-ysis is finished . But first conclusions can be drawnalready from the measured cross section ratios for C,Cu, Au targets .

y0.3

0.4

02

100 200 300 400 Soo

pK, (MeV/c)

Figure 4: The K+-production cross section forp(1.OGeV)C -+ K+X as a function of kaon momen-tum.Measurements with different targets were performedwith the same geometry of ANKE spectrometer andits detection system and the same settings ofthe pro-ton beam . Therefore ratios of the kaon productioncross sections for various nuclei as a function of kaonK+momentum a (pK+) are equal to the correspond-

01cing ratios of kaon count rates in the individual tele-scopes normalized to pion production cross sectionratio at a momentum of 507±17 MeV/c detected intelescope 15 :

Cac)lil_CNCMA CNäl(is)Mc Ca'c/hs)

Pion-production cross sections ratios in pA collisionswith a momenta of 500 MeV/c in forward directionwere measured by several groups [3, 4, 5] in theproton energy range 0.73=4.2 GeV and are knownwith an accuracy better than 10% [6] . Fig. 5 showsthe deduced K+ production cross section ratios atTp = 2.3 GeV, i.e . above the N-N threshold.The momentum integrated cross-section ratios are:

R = 3.23 ± 0.35 for Cu/C

R = 6.29 ± 0.70 for Au/C .

17

0 6

X 5

4

3

2

Preliminaryc~/c2 .3 GeV

~~i+t+++

+ ... ..~.. .. ..:}:+

0.Z 794 6

5432

o200 400 200 400

PK, (MeV/c)

pK, (MeV/c)Figure 6: Ratios of the K+ production cross sectionsfor Cu/C and Au/C as a function of the kaon mo-mentum for Tp = 1.0 GeV. The dotted line indicatesan is A2/3 dependence of the cross section.

PreliminarycU/c1 .0 GeV

References:

012

X 10

8

6

4

14X12

1086

R = 3 .9 ± 0.4 for Cu/C

R= 6.6 ± 0.8 for Au/C .

PreliminaryAuIC2.3GeV

2200 400

200 400px, (MeV/c)

PK, (MeV/c)Figure 5: Ratios of the K+ production cross sectionsfor Cu/C and Au/C as a function of the kaon momentum for Tp = 2.3 GeV. The dotted line indicatesan A2/3 dependence of the cross section.

a St.Petersburg Nuclear Physics Instituteb PhD student from (a)

PreliminaryAu/c

1 .0 GeV

These ratios are in a good agreement with an A2/ 3dependence of the total cross section, which is ex-pected if the kaons are produced via one-step mecha-nism . One observes a strong momentum dependence,possibly resulting from a rescattering of the producedkaons in the nuclear environment .Fig. 6 shows the ratios at Tp = 1.0 GeV. The mo-mentum integrated cross-section ratios are:

Unexpectedly, these ratios are also close to an A2 / 3dependence of the total cross section, but the mo-mentum dependence is quite different from what wasobserved for the ratios at Tp = 2 .3 GeV.

[1]

S. Baxsov et al ., submitted to NIM A.[2]

H. Junghans et al., IKP Ann.Rep.99, p.16.[3]

D.R.F. Cochran

et

al.,

Phys.Rev .

D6,3085(1972) .

[4] J. Papp et al., Phys.Rev.Lett . 34, 60l(1975).[5] V. V. Abaev et al ., J.Phys . G14, 903(1988) .(6] S. Barsov et al ., Acta Physica Polonica B 31,

2159(2000) .

Supported by . BMBF, DFG and Russian Ministry ofSciences .

Kaon production in the reaction p+C-4K++X hasbeen measured with the ANKE spectrometer atbeam energies of 2.3, 1.8, 1 .5, 1.2 and 1.0 GeV. Thecalibration of the data is still in progress, neverthe-less the detected and analysed Kaon rates can becompared with ROC-model [1] calculations if the ac-ceptance and efficiency of the detection process atANKE is taken into account. Thus the ROC-modelwas used as an event generator for GEANT simula-tions of the ANKE side-detector system .In Fig. 1 the detection efficiencies for kaons from suchsimulations are shown. They are plotted as a func-tion of the telescope number, normalised to the totalnumber of generated kaons. Curve b shows the num-ber of kaons generated in the acceptance range ofeach considered telescope . The difference to curve arepresents losses due to scattering and due to thegaps between the telescopes . Curve c takes into ac-count the loss due to cuts on time offlight andenergyloss in the scintillation counters . Curve d takes thelifetime of the kaons on their way through the detec-tor into acount . Curve e shows the kaons counted inthe veto counter with a decay time larger than 2.6ns . In comparison to the experimentally determinedkaon detection efficiency (L) [2] there are some sig-nificant discrepancies for telescopes 6 to 8 which maydepend on the slightly different cut parameters anddegrader thicknesses, while the dip at telescope 7 isvisible in both treatments .

0.08

w 0.04

0.02

Comparison of first results on K+ production at ANKE with model calculations

02 4 6 8 10 12 14

Telescope numberFigure 1: Simulation of the K+ detection efficiencywith the ANKE side detector as a function of thetelescope number. The curves are explained in thetext . The experimental data points (A) are from [2]and were normalized to curve a.

Very primilary results of the data analysis for beamenergies of 1 .0 GeV and 1.2 GeV are shown in Fig. 2.The raw numbers of extracted kaons for the spec-ified data collecting time are plotted as a functionof the mean particle momentum measured in everytelescope . A preliminary normalisation to compara-

Ch. Schneider« , H. Müller', M. Büscher

ble experiment conditions results in a factor of N 30[2] between the cross sections at the two energies .

Hs600

400

200

Figure 2: Number of identified kaons in each tele-scope from the experimental runs at 1.2 and 1.0 GeV[3] .

The cross sections obtained from the ROC-Geantsimulations are plotted in Fig. 3. They take into ac-count all losses described in Fig. 1. The ratio of themeasured production rate at 1.0 GeV and 1.2 GeV atthe covered forward angle around 0' is comparableto the prediction of our simulations.

10 " ~

ö- "6C 10vb .7*10

-s10

175 250 325 400 475Momentum )Mevlc)

References :

f f

2.0 GeV

1.0 GeV

1.0 GeV

`~

1.2 GeV

C Target

4 6 R 10 12 14Telescope number

Figure 3: Simulated detection cross sections, whenthe ROC-model is used as a generator for GEANTsimulation of the ANKE spectrometer.

[l] H. Müller, Z. Phys . A 355, 223 (1996) .[2]

M. Büscher et al ., publication in preparation forNIM A; M. Büscher, H. Junghans et al ., contri-bution to this annual report .

[3]

S . Barsov et al ., Nucl . Phys . A 675, 230 (2000) .

Forschungszentrum Rossendorf, Institut für Kern-und Hadronenphysik, Dresden, Germany.

Measurement of ds or/(dpp - dfp - dn,r+) at 0° at ANKE and estimation of the spin-singlet/tripletfinal-state ratio in the reaction pp -> pn?r+ at pbeam - 1.08 GeV/c

The study of meson production in pp collisions givesan opportunity to gain a better understanding ofmeson-nucleon dynamics and, in particular, the ef-fect of the nucleon-nucleon interaction in the nucleonoverlap region [1] . Here we consider the question ofthe relative intensity of the two S-wave spin statesof the final pn-system in the pp -+ pn7r+ reaction atPbeam ~-- 1.08 GeV/c.To estimate the spin-singlet/triplet ratio, we used asubsample of events, obtained with a CH2 target .In the lab. system the 7r+-meson and proton wereemitted close to 0°, software cuts restricting bothangles to 0 < 2° . According to [2], at low pn relativemomenta, the variation of the cross section is deter-mined by final-state interaction (FSI) between thetwo nucleons, which can be in either S =1 or S = 0states .The momentum distribution of protons produced inpp -+ pn7r+ reactions in a CH2 target is shown inFig. 1. The analysis of the data from a carbon targetshowed that the background is ;:zi 2.5% and can beneglected.

2 ietla

isoöS140e2 120

!Go

e0

69

40

20

M.Biischer, S.Dymova, V.Komarova, V.Koptevb, V. Kurbatova, M.Nekipelovb,H.Str6her, C.Wilkin°, Yu.Uzikova, S.Yashenkoa

g0

42Q

340

360

aso

400

490

440

460Proton momentum,MWlc

tiX2 =

(Ni

_Nmeas)2/ Nmeas8

t

2

Figure 1 : Momentum distribution of protons fromthe pp -+ per+X reaction . The error bars indicatethe momentum bins (horizontal) and the statisticaluncertainties (vertical) . The different histograms aredescribed in the text .

In order to extract the singlet/triplet ratio 6 fromthe data shown in Fig.1, a x2 form,

was minimized as a function of one parameter ~ .Nmeas is the measured number of events in the i-thbin of the histogram and Nth the predicted number .

The minimum was found for 6 = 0.001 f 0.010with x2 /ndf = 15.4/20. The fit shows that the sin-glet/triplet ratio 6 < 0.03 at a confidence level of99%. Note that our estimate of the ratio is based onthe shape of the proton-momentum spectrum, whichavoids possible uncertainties from the cross-sectionnormalization .The dashed histogram in Fig. 1 shows the result ofthe fit with 6 = 0.001 ; the dotted histogram showsthat obtained using the statistical value of 6 = 1/3.

a n

8iö 34o 360 380 400 420 440 460Proton momentum, 6teVlc

Figure 2: Differential cross section of protons fromthe reaction pp -} pn7r+ at 0° in the lab system .

We also extracted from the measured data the dif-ferential cross section dla/(dpn , dQp - dQ,r+) at 0°shown in Fig. 2. The curve gives the prediction fortriplet np final states using the known cross sectionof the pp --> dir+ reaction [3]. This approach alsoproves that ~ is at most a few percent at this mo-mentum.

References :

[1] H. Machner, J. Haidenbauer, J.Phys.G . 25(1999) R231.

[2] M.L . Goldberger and K.M. Watson, CollisionTheory, (Wiley, New York, 1969), p. 549.

[3] A. Boudard, G. Fäldt, C . Wilkin, Phys.Lett.B389 (1996) 440.

a JINR, Dubna, Russiab PNPI, Gatchina, Russiaa UCL, London, WC1E 6BT, UK* Work supported by WTZ grant KAS-001-099

Luminosity determination at ANKE via the reaction pp -4 dir+

A. Khoukaz", N. Lang"

After the installation of the cluster target at theANKE facility [1], first data on the single pion pro-duction in the proton-proton scattering have beentaken at a beam momentum of 1.083 GeV/c using ahydrogen cluster beam as target . One aim of thesetest measurements was to investigate the possibilityof using the reaction pp -} d7r+ as reference reactionfor data normalisation purposes .To extract events of the single meson productionchannels pp -+ d7r+/pn7r+, events have been selectedwith the signature of one detected 7r+ meson in theside detector of theANKE facility. The particle iden-tification was performed using the time-of-flight in-formation, obtained with the start and stop scintilla-tion hodoscopes, and the corresponding energy-lossinformation in the scintillator hodoscopes . The mo-menta ofthe pions, observed in a set of two multiwireproportional chambers, were determined by tracingthe tracks of the ejectiles back through the knownmagnetic field to the interaction point. By this, afour-momentum vector determination of the detectedpions was possible and the missing mass of thesystem of unobserved particles could be calculatedas demonstrated in Fig.1 (upper spectrum). As ex-pected, on top of an almost flat background distribu-tion, arising from the reaction channel pp -+ pn7r+, asignal from the pp --> d7r+ reaction is clearly visibleat the mass of the deuteron .The observed structure of the missing-mass distribu-tion reflects the segmentation of the stop scintilla-tion hodoscope. Requiring a coincident detection ofa deuteron hit in the scintillation hodoscope of theforward detector, an almost clean selection of d?r+events with a missing-mass resolution of 4.6 MeV/c2(FWHM) was possible (Fig .1, lower spectrum) . Theobserved shift of the deuteron missing-mass peak byAm = 3.6 MeV/c2 corresponds to an inaccuracy ofless than 0.2%.To determine the luminosity, the differential crosssections of the corresponding reaction channel mustbe known and the number of extracted events has tobe corrected for the acceptance of the detection sys-tem, which was determined by using Monte-Carlosimulations. For experimental reasons, during thistest beam time both the target beam density as wellas the COSY beam intensity have been far from op-timal, resulting in a relatively low luminosity. Nev-ertheless, during the discussed test run nearly 47000d ,7r+ events have been accumulated in less than 7hours of beam time, corresponding to a luminosityof L = 5.8 . 1028 cm-2 s-1 f8% [2] . In following beamtimes with improved conditions, luminosities beyondL = 103° cm-2s-1 have been reached [3] . Both thequality of the spectra as well as the good statistics incombination with a rich data base for the pp -+ d7r+reaction demonstrate the applicability of this methodfor the luminosity determination at ANKE.

ä 9000

8000

7000

6000

5000

4000

3000

2000

1000

1840 1860 1880 1900 1920 1940 1960 1980missing mass [MeV/c21

with coincidence

FVVHM-4,6MeV/d

1840 1860 1880 1900 1920 1940 1960 1980deuteron mass

missing mass [MeV/c2 1

Figure 1: Missing mass distribution of the reactionpp -+ 7r+X at abeam momentum ofp = 1.083 GeV/cfor events with and without a coincident detection ofa deuteron hit in the forward detector .

References:

[1] H.H. Adam et al ., IKP/COSY Annual Report1999, FZ-Jülich, p. 20 .

[2] N. Lang, diploma thesis, Westfälische Wilhelms-Universität, Münster, Germany, (2000) .

[3] R. Schleichert, private communication (2000) .

" Institut für Kernphysik, Westfälische Wilhelms-Universität, Mfinster, Germany

Binary process registration in the forward scintillation hodoscope at ANKE

The forward two-plane scintillation hodoscope at theANKE setup was described earlier in Ref.[1] . Here wepresent the calibration procedure and the particle-identification capability of the device at a beam en-ergy of T = 0.5 GeV. For the amplitude calibra-tion we define a form and parameters DE = fi(A),where AE is the energy deposited by a particle in thei-th counter and A the amplitude of the responsesignal . Four sets of most probable (mp) values ofamplitude distributions from binary processes havebeen considered for each counter: forward and back-ward (in c.m.) produced deuterons from the reac-tion pp --} d,7r+ at T = 0.5 GeV and protons frompp -> pp at T = 0.5 GeV and 2.0 GeV.Initially, the following transformation has been ap-plied to each measured amplitude Qi to equalize thesignals from the upper (U) and lower (L) photomul-tiplier (PM) of each counter (i)

Ai = co (Qi + pc - pi) (Mi +pc - pi) -1 .

Here co is the constant to which the most probableamplitudes Mi caused by minimum ionizing parti-cles were equalized, pc is the constant pedestal sub-tracted during the data readout and pi is the actualpedestal for each channel, measured beforehand . Af-ter that the mean amplitude A was calculated foreach counter: A = 0.5 (AU + AL). This summingcancels the main part of the PM signal amplitudedependence on the vertical coordinate of the parti-cle hit in the scintillator . To minimize the remainingnonlinearity we used the following correction : Ao =A/(1 +0.22y2) . Here y is vertical coordinate normal-ized to the range [-1, +1], which was defined by theCFD time signal difference : y = 0.5 a (TL -TU) . Theconstant a corresponded to the effectve propagationspeed of light which is equal to 15 cm/ns.For each of the binary processes mentioned above, aMC simulation has been performed in order to de-fine the mp value of deposited energy in each counter,taking into account the kinematics of the processesand the geometrical counter acceptance . We foundthat at large (- 700 QDC channels) amplitudes, asmall nonlinearity occures (evidently caused by anonlinearity of the entire channel PM-FanOut) . Thisnonlinearity arises up to about 10 % of the energy de-posited by slow deuterons . So we chose the parabolicfit function for the AE = f(A) function and de-termined the corresponding coefficients for each ofthe 17 counters . The mean value of x 2 per degree offreedom, characterizing the fitting quality, is equalto - 1 .2 .In Fig.1 an example of the event distribution fora counter in the first (No.3) and the second plane(No.4) is presented . The three correlated intensivepeaks correspond to binary processes at T = 0.5GeV: elastic protons (lower peak) andthe deuterons .At the lower edge of the plot even a low intensity pion

V. Komarova, G. Macharashvilia ,b

peak is seen . The spectra contain also a continuumcaused by protons from pion-production processes.

Figure 1 : Plane 1/Plane 2 Correlated AEIt is evident that averaging of the calibrated signalsfrom the 1st and the 2nd planes of the hodoscopewill improve the deposited energy resolution . Strictlyspeaking, the averaging procedure is not correct be-cause slow particles (deuterons) loose energy in thefirst plane of the hodoscope which increases the en-ergy loss in the second plane. Nevertheless, we canaverage these two values for particle identification .In Table 1 the cumulative amplitude characteristicsfor the forward hodoscope are collected . They showthe accuracy of the most probable deposited energy(AEmp) determination and the widths of the AEdistributions.

Table 1: Energy resolution of the forward hodoscope

It is seen that simultaneous use of the data from theboth planes decreases the sampling fluctuations by afactor of about v'2-, as should be expected .The described calibration procedure allows to anal-yse the deposited energy in the hodoscope indepen-dent of the individual counter number or the verticalposition of the particle hit point. The achieved fairlyhigh accuracy of the energy loss determination maybe effectively used for particle identification in theANKE forward detector.References:

[1] V.Komarov et al . IKP Annual Report 1998 .Jülich 1999 . p.69

'JINR, Dubna, RussiabHEPI TSU, Tbilisi, Georgia

Particle Plane DEmp, MeV/cm FWHM, %

dsioW 1 st 9.04 f 0.47 120.8 GeV/c 2 nd 9.67 ± 0.67 16

Both 9.60 f 0.45 11dfast 1 st 5.97 f 0.49 19

1.14 GeV/c 2 nd 6.37 f 0.55 20Both 6.10 f 0.38 15

p 1 st 2.77 ± 0.29 241 .07 GeV/c 2 nd 2.82 ± 0.30 25

Both 2.80 f 0.20 17

Momentum dependent efficiency of the forward Cerenkov counters at ANKE

M.Biischer, S.Dymov, A.Kacharava",b , V.Komarova, G.Macharashvilia,b, M.Nioradzeb , R.Schleichert

Theforward Cerenkov hodoscope at the ANKE setupserves for the identification of fast forward ejectiles.In experiments on meson production in pp interac-tions [1, 2], deuterons have to be separated from pro-tons, both with momentaabove the Cerenkov thresh-old in the radiator material (plexiglass) . A new typeof Cerenkov counters, based on total internal reflec-tion, is used for that purpose. Such counters havebeen proposed for use at ANKE in 1994 [3] andare described in detail in Refs . [4, 5] . They wereused recently for proton suppression and to identifydeuterons in the momentum range 1.7-2 .3 GeV/cfrom the reaction pd -+ pspdw at 2 GeV beam en-ergy.Here we describe the procedure of measuring the ef-ficiency of proton identification in a wide momen-tum range including the range mentioned above andalso in the range 0.85-2.15 GeV/c, where the protonshave the same velocity (and, thus, efficiency) as thedeuterons of interest . During the calibration mea-surements all counters (8 upper and 8 lower) werepositioned under the same inclination angle of 10° .The detection efficiency is defined as follows :

1 +00sk (Qth, P) -`-

Nf

sk (Q, p) dQ ,Qih

where sk (Q, p) is the Cerenkov amplitude spectrumof protons with momentum p in counter number k;Qth is the amplitude discrimination threshold, andNk represents the number of protons hitting the k-thcounter . The number Nk and the spectrum sk (Q, p)were determined for events satisfying the followingcriteria : i) straight-line track reconstruction can beachieved in the forward proportional chambers ; ii)the track corresponds to a particle with momentum pcoming from the target (selected by a 'vertical' selec-tion y/yi criterium and passing through the exit win-dow of the vacuum chamber) ; iii) the track hits cor-rect forward scintillation counters in the both planesand the particles have proper energy losses ; the trackhits the k-th Cerenkov counter excluding an edgearea of 0.5 cm width and 1.5 cm distance to the me-dian plane of the setup. The signal spectra for eachcounter were equalized to use the same threshold forall spectra.In Fig.1 the measured momentum dependence of theproton-detection efficiency is plotted. To cover thefull momentum range with overlapping sub-intervals,data obtained at three values of the beam energyhave been used . Some nonregularity of the mo-mentum dependence can be explained by the pres-ence of a relatively small contamination of back-ground events with improper momentum reconstruc-tion . The efficiency shown is determined at a low cutlevel Qth = 8 QDC-channels (the mean amplitudefor 2GeV/c protons is at about channel 200) .

Amplitude Cut Level 8 ch . QDC

IJINR, Dubna, RussiabHEPI TSU, Tbilisi, Georgia

0.5 1 1.5 2 2.5' 3Accepted Proton Momentum

GeV/c

Figure 1 : Proton detection Efficiency at Qth = 8 ch

At this cut level the achieved efficiency at 2 GeV/cbeam momentum is about 95% and about 35% at1 GeV/c. The signal amplitudes at low momenta(close to the radiation threshold at 0.85 GeV/c), arerelatively small. Therefore, using of a proper sig-nal discrimination allows to get a significant (10-20times) proton rejection in the momentum range ofinterest with a small loss (- 10%) of deuterons inthe same range.References:

[1] COSY Proposal #55, "Study of w and q5-meson production in the reaction pd -+ dVpBP atANKE", (1998) .

[2]

COSYProposal #75, "Study of ao-mesons in thereaction pp --> dao -+ K+I{°", (1997) .

[3] N . Amaglobeli et al ., "New type of Cherenkovcounter of total internal reflection", PreprintHEPI TSU 08-94, Tbilisi (1994) .

[4] A. Kacharava et al ., "Beam test of Cerenkovcounter prototype for ZDF setup", NIM A376,356 (1996) .

[5]

R. Esser et al ., Annual Report 1999 of the IKP,p.29 .

Simulations of the inclined Cerenkov detectors for p-d separation in forward direction at ANKE

The forward detection system of ANKE is equippedwith Cerenkov detectors for the separation betweendeuterons and protons in reactions like pp -3 dX,where X can be an (unobserved) meson, e.g. w oraä [1]. To understand their behaviour and to opti-mize the setup, a simulation program in C++ wasdeveloped, based on a program used for simulationof the Cerenkov counters in the K--detection systemof ANKE [2].In the simulation, particles (p or d) are tracked fromthe target through the magnetic field of D2, thus giv-ing realistic incident positions, momenta and angulardistributions on the detector . The initial momenta ofthe particles at the target are obtained from a phase-space simulation of the reaction at different beamenergies . Position, size and inclination angle of thedetector can be chosen by the user as a free param-eter . If any particle hits the detector with ß >-I,the resulting Cerenkov photons are placed randomlyon a cone around the particle path with an open-ing angle cos 00 = än . The number of photons perunit

ath length depends on the particle's velocityvia -~m̀

= 370 - sin 2t9c as the mean value of aPoisson-distribution . Every photon is tracked insidethe material until it either reaches the photo multi-plier (PM) or is lost . Photons reaching the PM aredetected (and counted) with an efficiency of 20%. Toobtain a more realistic detector response, several pa-rameters were implemented:e Photon loss : Due to surface impurities, photonsmay not be reflected at a detector surface even ifthe incident angle is larger than the total reflectionangle. This probability has to be treated as a freeparameter and is non-zero [3]. It was chosen to be15% for each reflection, such that the resulting spec-tra have approx . the same peak height/FWHM-ratioas the experimental ones . The average number ofreflections per photon is 10 . . .15 (without photonloss). Photon loss in the material itself sums up to:.,2% only, because the attenuation length for luciteis N2m. This mechanism was also implemented." Variation of angle: Due to surface impurities, theangle of a photon trajectory relative to the surfacemay change locally. This is simulated by a randomchange : We[-1° ;1°], using a Gaussian around 0°,cut at f1°. This value was estimated from experi-mental data [3] . This mechanism shifts the spectrato smaller amplitudes and reduces the FWHM, butcauses smaller effects than the photon loss probabil-ity." Minimal path length : To avoid edge effects, onlyparticles with path lengths >5cm are accepted . Inthe analysis of the experimental data [4] a differentcriterion was applied: only hits on the front side witha distance of 1.5 cm and 0.4 cm from the vertical andhorizontal edges, respectively, were accepted . In prin-

C. Leim

ciple, both methods are equivalent and the latter willalternatively be implemented.The resulting spectra are shown in fig.1 (solid line)and are similar to the experimental distribution(dashed line) . The measured data, however, show atail of low-rate signals starting from channel zero,which cannot be found in the simulation . The reasonfor that may be a wrong value for the photon lossprobability or a too optimistic value for the PM effi-ciency.Thespectra differ from those of an ideal Cerenkov de-tector, which is simulated with all parameters men-tioned above set to zero . It that case (dot-dashed linein fig. 1), the peak is shifted towards larger ampli-tudes. The tail at the low-amplitude side of the peakis caused by events with path lengths <5cm.Future plans involve examination of polarization ef-fects (which might yield an explanation of the empir-ical photon loss parameter) and small-angle scatter-ing in the detectors in front of the C-counters (whichmight cause the low-signal tail) . The response fordeuterons (which should be close to zero) and otherbeam enenergies and parameters (in particular theinclination angles) will also be investigated .

50

40

Ü .0~

20

10

Y!

110

L

~, .sil . rt1m17WF:a a _

I

L

10

20

40

60

80

100

120

140 '160Detected photons (simulation) / QDC ch . (experiment)

Figure 1: Simulated and measured detector response :protons at abeam energy of 2000 MeV for an inclineddetector (angle : 10°) . The solid histogram shows arealistic simulation with all effects switched on (seetext), whereas the dot-dashed histogram is obtainedwith all parameters set to zero . The experimentalresults are shown in the dashed histogram.References :

V.Kleber et al ., contribution to this reportH.R.Koch et al ., IKP annual report 1999, p .28M.Hennebach: Untersuchungen zum Einsatzvon Cerenkovzählern mit Totalreflektion für dieTeilchenidentifikation an ANKE, Diploma the-sis Univ . Köln, Dec. 1999

[4] G.Macharashvili et al ., contribution to this re-port

Methods to determine drift characteristics of the ANKE drift chambers

V . Komarov', A. Kulikov', V. Kurbatov', H.Ohm, A. Petrus', S . Yaschenko', B . Zalikhanov'

An important task for the analysis of drift-chamberinformation is the determination of their drift char-acteristics (drift-distance to drift-time relation R(t)).The construction and the results of radioactive-source tests of the drift chambers for the ANKEbackward detector were described in [1] . In order tostudy the influence of the magnetic stray field of theANKE magnet D1 on the drift characteristics, a sim-ulation has been made using the Garfield program.It turned out that the influence of the magnetic strayfield is negligible under the conditions 'at ANKE. InFig.1a the calculated drift characteristics is shown.The obtained drift velocity (50 pm/ns) is in goodagreement with the experimental results[1] . Thesedrift characteristics can be used for simulations oftime spectra of the ANKE drift chambers .Let us briefly describe several methods which maybe used to determine of drift characteristics of thechambers used at ANKE. All these methods use onlythe time information and the numbers of the wireswhich fired .- "Autocalibration" method.This method is based on the analysis of time spectra[2]. Assuming a uniform particle flux within the driftcell, the time spectrum represents the drift velocityas a function of drift time . The integral of the timespectrum (with normalization coefficient F) is thecoordinate dependence on the drift time (d is thelength of the drift cell) :

d

t dN

T - dNR(t) = F f dTdT

(_

)F=~ dT dT ,To

To- "Iterative" method.This method allows to determine R(t) from parti-cle trajectories . Starting with some initial Ri (t), thetrack parameters are reconstructed which allows toobtain the dependence of the coordinates from thedrift times. Subsequent averaging of this dependenceleads to a new approximation of R2 (t) and so on .The convergence of this method strongly depends onthe initial approximation of R(t) .- "Analytical" method.The problem of the determination of R(t) by trajec-tories can be solved in another way using an analyt-ical representation of X2

min in the space of the trackparameters . This method is fully equivalent to the"iterative" one, but requires less computation timeand does not depend on any initial approximations .For a statistical sum of K trajectories (in straight-line approximation) X2

min has the following form [3]1 K N N

2Xmin = K

xlkClixikk=1 l-1 i=1

)xik = wik+SikR(tik) i Cli

(ZN(z2

(ziz2)z ,

xik, zi are the x and z-coordinates of the i-th driftchamber, sik is the "left-right ambiguity" coefficient

(sik=:i:1), wik is the wire position and N representsthe number of the chambers .If R(t) has the linear form R(t) = V(t - To) and thedrift velocity V and time delay To are the same forall wires, the minimization of Xmin leads to a systemof two linear equations. In the case of individual driftcharacteristics for each wire, one obtains a system of2 - N- M linear equations (M is the number of wiresin each drift chamber) .All three methods were tested with simulated data .Pions with randomly generated momenta and an-gles were traced through the magnetic field of theANKE dipole D1 using the GEANT program andmeasured 3d field maps. Multiple scattering and in-teractions in matter were taken into account. The co-ordinates in the drift chambers with measuring errors(100 pm) were used as the "true" ones . Drift cham-ber time values were simulated using the drift char-acteristic shown in Fig.1 . These times and the wirenumbers were used for redetermination of the drift-chamber characteristics and calculation of the coor-dinates. In Fig.1b and c the results of comparisonbetween the calculated coordinates and "true" onesfor the "autocalibration" and "analytical" methodsare shown. The accuracy of the coordinate determi-nation is -330 pm for the "autocalibration" methodand -130 ym for the "analytical" one. Subtractingthe squared measuring error (100 jim) one can cal-culate the accuracy of the methods .

Fww"a

Figure 1 :References:

Characteristics of chambers and methods.

[1]

V.Abazov et al ., IKP Annual Report 1998, p-18-

[2] F.Sauli, LERN 77-09, Geneva, p.78.

[3] Yu.Yatsunenko, Comp.Phys.Comm. 118 (1999) .

'JINR, Dubna, Russia

S. Barsov', S. Dymovb, I. Lehmann, S. Merzliakov', A. Mussgiller, D. Protic and R. Schleichert

Using the deuterium-cluster-jet target at ANKE, onecan tag reactions on the neutron by identifying theso-called "spectator proton" in a near-target silicontelescope . Themeasurement of the kinematical prop-erties of this proton allows to determine the excessenergy in the pn-system . The use of the forward de-tection system enables studies on pd -+ pspdM iden-tifying the undetected meson "M" by the missing-mass method.The near-target telescope has been used at ANKEduring 2000 to detect and identify low energetic par-ticles at angles close to 90°[1] . The telescope com-prises a 60 /.tm thick surface barrier detector with450mm2 active area as a first layer and two stripdetectors of 300pm and 5mm active thickness . Thisallows to identify protons and deuterons at kineticenergies between 3MeV and 40 MeV. Apart from theneutron tagging, this setup provides a good tool forthe luminosity monitoring at ANKE[1, 2] .

D 2 -target

MWPC'8

°(i 8 C-hodoscope det.

Figure 1: Detector setup at ANKE to measure the reac-tions: pd -3 p,pdM for M=7r°, 77, co

In fig . 1 the vacuum chamber of the main ANKEmagnet D2 and the relevant detectors are sketched .The forward-detection system with three' multi-proportional-wire chambers (MWPC) and a ho-doscope consisting of two layers of scintillators hasbeen extended by Cerenkov detectors to distinguishprotons and deuterons[3] .

1600 -

1400

1200 pd->peppn1000

800 .

600

400

200-

0' 600

800

1000 1200 1400 1600 1800

missing mass pd->p,,pX [MeV/c21Figure 2: By the identification of a spectator proton thepeak from pn-elastic scattering can be clearly identifiedin the missing-mass spectrum .

mean : (94046) MeV/c'

twhm: (86+IS) MeV/c2

At several beam energies the well known kinematicsof pp elastic and pp-I "d7r+ could be used during thefirst test-beam time for w-production in September2000 to obtain :

'Two chambers have been used in Sept . 2000 . The 3rdchamber has been installed in Dec. 2000 .

Meson Production on the Neutron at ANKE

" alignment and efficiency calibration of the in-clined Cerenkov counters,

" energy calibration of the forward hodoscope," a verification of the tracking and momentum

reconstruction (see fig . 2),Additionally a preliminary result for pd --> pspdir°at 1 .1 GeV/c could be obtained . In fig. 3 (left) themissing-mass peak from the 7r°-production is shown,sitting on a clearly distinguishable background dueto misidentification of protons as deuterons . The cur-rent analysis will yield together with existing data agood cross check of the reliability of the analysis andsimulation tools at ANKE.

pbeem =1 .1 GeV/c

pneem = 2.772 GeV/c

so r

040Gd 30

20

10

0

0 .0

50

1100

150

200

250

1

650

700~ -750 "

800 ~

850

missing mass pd->p,pdX [MeV/c 2] .Figure 3: Missing mass spectra from .7r°-production at1.1 GeV/c and w-production at 2.772 GeV/cIn the case of w-production the deuteron identifica-tion is a much more delicate task and, furthermore,the meson peak is much closer to the kinematicallimit. The right spectrum in fig. 3 contains the to-tal number of events taken in Sept . 2000 . Unfortu-nately, a COSY and target breakdown did not al-low us to take more statistics. Thus the expectedw-peak with a width of approx. 20 MeV (FWHM)can not be clearly separated from background . As afirst statement the data evaluation shows, that thetotal cross section for w-production in pd -+ pspdw atQ = 40 MeV has to be estimated lower than 10 pb.2One week of beam time has been allocated for Au-gust 2001 to gain a first result on cross section andobtain an estimate for the total statistics needed tocomplete the measurements on w-cross section. Ad-ditional beam times for 7r°- and 77-production areplanned and have been approved by the PAC.References:

Studies on a Detection System for Spectator Pro-tons at ANKE, Diploma thesis by LLEHMANN, FZJInterner Bericht - FZJ-IKP-IB-E2-1/2000

[2] Luminosity Determination at ANKE with the Spec-tator Detector, IKP/COSY Annual Report 1999,FZ-Juelich (Ail-3744), page 21 .Momentum dependent efficiency of . . . Cerenkovcounters at ANKE, contribution to this report

'PNPI, Gatchina, Russia; bJINR, Dubna, Russia .21n the original proposal simulations have been done with

a cross section overestimated by a factor of five at least.

S. Barsov, T. Krings, I. Lehmann, D. Protic, S. Merzliakov, A . Mussgiller and R. Schleichert

For the ANKE experiment a vertex detector basedon double-sided silicon strip detectors [2} is underconstruction [1]. The original motivation in 1999 was,to built a vertex detector around the extended targetregion of the storage cell of the polarized AtomicBeam Source ABS [3] .

ABS

Combined Spectator and Vertex Detection at ANKE

Figure 1 : The ANKE Vertex detector around the 40cmlong storage cell of the Atomic Beam Source

The use of a 40 cm long strorage cell provides about100 times more luminosity compared with the mereatomic beam. But it can only be used together with avertex detector which determines the vertex of eachindividual reaction and which must distinguish be-tween interactions of the COSY beam with the po-larized gas and the wall of the cell .The additional identification and tracking of low en-ergy protons will allow to use polarized deuterons asa polarized neutron target [4] and therfore e. g. tostudy reactions of the type pn --; pn or pn -+ dX.The basic design considerations for the silicon vertexdetector are

" MIP tracking within the ANKE spectrome-ter magnet D2 with Op/p < 1%. 3 planes of300pm thick detectors.

" DE deuteron identification in forward direc-tion (pn -+ dX) s. fig . 3 (one plane of 5500 /cmthick detectors) .

" AE/E proton identification (3-40 MeV) . Tele-scope structure of 65/300/5500ym thick detec-tors in the barrel region .

" Time of flight particle identification with a res-olution of < 1 ns FWHM. This implies the de-velopment of dedicated preamplifiers.

Fig. 2 shows the forward tracking system within theANKE magnet D2. Three planes of 300pm thickdouble-sided silicon strip detectors will determine thetrack and therefore the momentum of the particles .An additional plane of 5600 pm thick double-sided

. .. .

M.~ ;1:

'&.,nia'11r~

~~"

Figure 2: Three 300pm plus one 5500 pm thick planesof silicon detectors within the magnetic field of D2 .

Figure 3: With the good intrinsic energy resolution ofthe 5500 pm thick silicon detectors, it will be possible todistinguish between protons and deuterons by AE onlyup to 2.5 GeV/c.silicon detectors [2] will be used for deuteron identi-fication via DE.The main goals for the year 2001 are

" Check new electronics for time of flight mea-surements with a resolution < 1 ns FWHM.

" Mechanical construction of the vertex detector .

" Assembly of a cooling system for the in-vacuumchip electronics.

References:The ANKE Vertex homepage,http://ikp442.ikp.kfa-juelich .de .

[2] Semiconductor Detectors, contribution to this re-port .The Polarized Internal Gas Target for ANKE, con-tribution to this report .

[4] Meson Production on the Neutron at ANKE, con-tribution to this report .

0 .15

0 .1

0.05

0

2.0 GeV/e

1

0 .15

0 .1

0.05

all.J `~

-I

oL,_J

P

2.5 cevie

1.5 2 2.5 3 3 .5 4

1 .5 2 2.5 3 3 .5AE.MeV

AE,MeV

" Check the final layout of the read-out chips.

" A first set of the 65/300/5500pm thick double-sided silicon strip detectors has to be assembledand tested in the proton beam of the Colognetandem accelerator.

The aim of this work is to test the particle-momentum distribution in the side telescopes [1] ofthe ANKE spectrometer .The momenta were calculated from the time-of-flight(TOF) information between the TOF-start and stopdetectors[1] . Data were taken at proton beam ener-gies 2.3 GeV. The value of the magnetic field in thespectrometer dipole D2 was 1.57 T.Figure 1 shows the TOF spectrum between the startcounter 15 and the stop. counter 13 . Most of the par-ticles are pions (peak around channel 250) and pro-tons (peak around channel 400) stemming from thetarget . Figure 1 shows the TOP spectrum withoutany cuts on scintillator or MWPC information.N

300

200

100

100

200

300

400

500

channels, 44 pstch

Figure 1: TOP spectrum between start counter 15and stop counter 13 .All particles going through a certain start-stop com-bination have the same momentum [2]. This momen-tum can be calculated from the time difference be-tween pion and proton peaks for each allowed start-stop combination [2] .Figure 2 represents the calculated momentum for allallowed start-counters and telescope 13 . The samedistributions were accordingly calculatedfor all othertelescopes .

Determination of particles momenta from TOF measurements for ANKE*

10

15

20

Start counter

Figure 2: Distribution of particle momentum intelescope 13 .The errors are due to the inaccuracy of the proton-and pion-peak positions (f2 channels) . This is equalto +7 MeV/c for telescope 13 . Since the telescopesare located along the focal surface of D2 the particlemomenta in a certain telescope must be the samefor all start counters . Some small divergence can be

P. Fedoretsa, M. Bfischer, V. Koptevb, V. Chernysheva

explaned by the :3 % nonlinearity of bin width ofTDC from mean value.Figure 3 represents the comparison of the resultsof TOP method with ray-tracing calculations usingGEANT [3].

700

5 500

300

100 0

b

0

5

10

15

TelescopeN

Figure 3: Comparison of the results of the TOPmethod with ray-tracing calculations . The verticallines axe the momentum ranges deduced from theGEANT simulations. The open symbols show the re-sults obtained from the TOP spectra with (squares)and without (circles) corrections for energy losses .The energy losses of particles in air and in the startcounters decrease the momentum of particles in thefirst telescopes . Pion energy losses are small. Theyare less than 1 MeV for all telescopes . However, slowprotons have quite big energy losses . After correctingfor these energy losses the results ofthe TOFmethodcoincide with the GEANT predictions.Summarizing, the TOPmethod of momentum recon-struction confirms the GEANT predictions of parti-cles momentum distribution in the telescopes .References :

M. Bfischer et al ., contribution to this AnnualReport, p.

[2] M. Bfischer et al ., Annual Report 1998, IKP,Forschungszentrum Jülich, p. 12 .

M. Bfischer et al . "Identification of K+-mesonsfrom subthreshold pA collisions with ANKE atCOSY-Jülich",NIM (in preparation) .

"Institute of Theoretical and Experimental Physics,Moscow.6St.Petersburg Nuclear Physics Institute .*Supported by grants RFFI99-02-18179a,DFG-443RUS-113,WTZ-RUS-99/684

1 800 I-T~Id

700

ad 600

500

400

300

0.164

0.163

0.162

0.161

0 .16

0.159

0.158

0.157

0.156

0.155

0.154

0.153

0.152

0.151

0.15

0.149

Reconstruction of Ejectile Momenta in ANKE Experiments

For the analysis of data from ANKE experiments, theinformation from the start and stop detectors (thelatter being positioned in the side-detection systemclose to the focal surface of the spectrometer dipole(1]) and from the hitted wires in two multi-wire pro-portional chambers (MWPC's) is utilized to deter-mine ejectile momenta.The momentum calibration of the spectrometer isperformed with "monoenergetic" pions from the two-body reaction pp -+ d7r+ . Such calibrations havebeen made for telescopes 6 to 15 and for low valuesof the magnetic field in D2, B = 0.6493 . . . 0.8946 T.The COSY-beam momenta were varied between0 .8262 and 1.1357 GeV/c. The 7r+ momenta fromthe two-body reaction are then between 0.12078 and0.35200 GeV/c, respectively. The momentum reso-lution is characteristic for the ANKE spectrometer,however, the accuracy of the obtained values dependson the method used for momentum reconstruction.Fig. 1 shows the results of a simulation using theANKE-GEANT (2] package. For stop detector #8,the dependence of the average ejectile momenta onthe start detector number has been determined . Thesame tendency, which is observed for other detectorsas well, is caused by the placement of the stop detec-tors a few cm in front of the focal plane of D2.

4 567691011121314START DETECTOR

Figure 1 : Dependence of the average ejectile mo-menta on the start-detector number, calculated forstop detector #8 and a proton-beam momentum of0.8606 GeV/c- The momentum of 0.15224 GeV/ccorresponds to the 7r+ momentum from the two-bodyreaction 0.8606 GeV/c pp -4 d7r+ .

In Fig. 2 momentum distributions in the start detec-tors are shown for the 0.8606 GeV/c p+p reactionfor stop detector #8. The calculated width of suchdistributions is -9% and it is almost independent onthe start-stop detector combination .Typical simulated distributions of hitted wires fromthe 0.8606 GeV/c p+p reaction are shown in Fig. 3.

I. Zychora

28

60

50

40

30

0.13

0.14

0.15

0.16

o.17

00.1a-"0.14 0:15

0.16 -0 .;TSTART 9

Swr 10

Figure 2 : Simulated momentum distributions (inGeV/c) for pions from 0.8606 GeV/c p+p reactionsobserved for stop detector #8 and different start de-tectors

Such distributions can be used to find inaccuracies inpositions of the ANKE detectors, the magnetic fieldshape, COSY beam momentum etc., by comparingthe simulated with measured distributions . For ex-ample, a beam momentum error of 1 %o causes a7r+-momentum difference between 7.0 and 2.3 %o ata beam momentum of 0.8262 GeV/c (value used tocalibrate stop detector #6) and 1 .1357 GeV/c (stopdetector #15), respectively.

70

60

50

~0

010

Figure 3: Simulated distributions of hitted wiresin the 1st (upper) and 2nd (lower) MWPC in the0 .8606 GeV/c p+p reaction for start detector #8 andstop detector #8. The narrower distribution corre-sponds to the plane with vertical wires in chambers,the broader one - with inclined .

To obtain the momenta of ejectiles detected in acertain stop detector, it is assumed that there is aunique dependence between the momentum and the6 hitted wires in the two MWPC's. A 2nd order poly-nomial of 6 variables with 28 coefficients is fittedthrough a set of simulated data points (were the ejec-tile momenta are known) with standard MINUIT.

The accuracy of the momentum reconstruction is es-timated in the following way: if we look for the hittedwires and allow for a difference in their numbers notlarger than 2 between wires in the same plane (thiscorresponds to realistic estimations of experimentaldetermination of the hitted wires), an accuracy ofthemomentum reconstruction was found not to be lowerthan 2.4% with multiple scattering included into sim-ulations and 2.0% without. The value from simula-tions with multiple scattering included depends onthe start detector and in most cases is about 3%.Fig. 4 shows a distribution of the momentum differ-ence for simulations of the 0.8606 GeV/c p+p reac-tion .

70

60

50

40

30

20

10

0-0.01 -0 .005 0

0

o r .

L1 .

1

''1-0.01

, -0.005

" 0

0.005 1

momentum difference ( GeV/c )

o.0os 0.01

0.01

Figure 4: Momentum difference for the 0.8606 GeV/cp+p reaction observed in stop detector #8 and start#13 for the difference in hitted wire number equalto 2 (upper) and 1 (lower) . The resulting momentumresolution (FWHM) is N3%.

Coefficients which are obtained from ANKE-GEANT simulations can be then used to reconstructmomenta from measurements but only for the setof events which fulfill conditions applied in simula-tions, especially only events with the same verticaland horizontal angle distributions must be chosen .Fig. 5 shows the reconstructed 7r+ momenta, both forsimulated and measured two-body events . It can beseen that the resolution for measured data is slightlyworse than the expected value. The reconstructedmomentum resolution is independent on the parti-cle type in the simulations. The momentum range ofparticles in the simulations should be broader thanthe expected momentum spread in the investigatedstop detectors .Information about the ANKE geometry andall programs necessary to make momentum re-construction can be found under the follow-ing address: http://ikpdl5.ikp.kfajuelich.de.8085/doc/Anke.html.

3000

2500

2000

1500

1000

500

700

600

500

400

300

200

too

0.14 0 .145 0.15 0.155 0.16 0 .165 0.17

0 .14

0.145

0.15

0.155

0.16

0 165

0.17

Ti momentum ( GeV/c )

Figure 5: Reconstructed momenta of 7r+ from the0.8606 GeV/cp+p two-body reaction (simulated andmeasured events) . The coefficients were calculatedfor stop detector #8 and start detectors #7,8 andthen applied for stop detector #8 and all start de-tectors.

References :

[1]

M.Biischer et al ., contribution to this report, p.

[2] I.Zychor, Annual Report 1999 of the IKP, FZJülich (2000), p.23

d The Andrzej Soltan Institute for Nuclear Studies,PL-05400 Swierk, Poland

pp -> dao+ -> d7r+ ?? .

Planned measurement of the branching ratio aö -.} ir+,q/K+K with ANKE*

Our plans to measure the branching ratio aö -4

?r+77/K+K and the a+-mass-mass distribution have beenapproved during the COSY-PAC meeting in May2000 . Two weeks of beam time have been grantedto study the branching ratio (February 2001) us-ing a cluster jet target (assumed luminosity : 31030cm-2s-1) . Three more weeks have already been allo-cated for the measurement of the aö-mass distribu-tion with high statistical accuracy using the frozenpellet target which will offer higher luminosities o£up to two orders of magnitude.The upcoming experiment in sight, further MonteCarlo simulations with ANKE-GEANT have beenperformed. Most recent calculations on the aö pro-duction cross section [1] in the reaction pp -> d aöyield a value of a ;:t~ 1.21cb at T=2 .6 GeV.

2.0

s 1.8" 1.6

1 .41 .21.00.0.60.2oa

0.90 0.92 0.94 0.96 0.98 1.00 1 .02 1 .04

OA0 .9

0.92 0.94 0.96 09S 1.00 1.02

V. Kleber, M. Biischer, V. Chernysheva, L.A . Kondr'tyuka

APImm� [GeV]

m, ., ., [GeV]

Figure 1: GEANT simulations on the reaction

In figure 1 (left side) the missing mass distribution of(pp,d) of an input file containing about 88000 sim-ulated pp -~ daö -4 d 7r+77 events is shown (dot-ted line). The distribution is that of a Flatte limitedat the high mass tail by the maximum COSY en-ergy. Additionally the remaining events after detec-tion with ANKE are plotted (solid line) . (Deuteronsare detected in the forward detection system, posi-tively charged mesons are identified in the side de-tection system .)On the right side of figure 1 the acceptance of ANKEas a function of the aö mass is shown. The accep-tance covers the full mass range and mainly is flat .Considering decay in flight, the detection efficiencyand assuming a branching ratio of 88% and 12% foraö -3 7rß'77 and aö -4 K+K, respectively, (withphase space corrections) the count rate is estimatedto yield 36 d7r+ events per hour .On the left, side of figure 2 the missing mass distri-bution of an input file containing about 12000 simu-lated pp -} daö -+ dK+K events is shown (dottedline) . The black lines are the events after detectionwith ANKE. The lowest distribution in this figure isobtained from those events where a K+ meson is de-tected in one of the telescopes of the side detectionsystem . The upper distribution contains additionallythose events where a K+ meson hits the sidewall .

29

4 s00

t 400

300

200

100

References :

30

,~ 2s

20

Is

10

s

0.98 0.99 1 .00 1 .01 1.02 1.03

0.98 0.99 1.00 1 .01 1 .02 1 .030

mm�, [GeV]

mN� [GeV]

Figure 2: GEAN_T simulations on the reactionpp -> da.0+ -4 dK+K.

Up to now it is not possible to identify K+ mesonswith the sidewall but Cerenkov counters have beeninstalled behind the scintillators and might help toselect the K+ mesons. This would roughly double thecount rate .The aö can only decay in K+K ifits mass is at leastthe sum of the kaon masses . Therefore, this mode isalso limited by the K+K production threshold (991MeV/c2).Again on the right side of the figure the geometricalacceptance as a funtion of the missing mass is shown.In both cases (with and without kaon detection withthe sidewall) it is flat and the whole mass range iscovered.The count rate of this decay channel is estimated toamount 11 dK+ events per hour. Thus it is expectedthat during two weeks of beam time we will be ableto detect about 7000 aö events decaying into 7r+27and about 2000 events decaying into K+K.The deuterons and a0 mesons axe mainly emitted ina relative P wave since in this reaction a S wave isforbidden due to conservation laws [1] . The P wavemanifests itself in an anisotropy in the c.m. deuteronangular distribution . The simulations show that withANKE this distribution can be detected in the rangeof about 10-180°. They also show that the initial an-gular distributions can be reconstructed and that theanisotropy is measurable .The still open question is about the character of nonresonant background . Due to the limited phase spaceit is hard to determine the contribution of non reso-nant reactions . Further investigations are going on.

[1] V.Grishina et al., Eur.Phys.J . A9, 277 (2000),nucl-th/0007074

'Institute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117259 Moscow, Russia*Work partially supported by BMBF (grant WTZ-RUS-684-99), DFG (grants 436 RUS 113/337, 436RUS 113/444, 436 RUS 113/561), INTAS (grantINTAS-98-500) and RFFI (grants 99-02-04034, 99-02-18179') .

Nonresonant 7r+77 production in the reaction pp ~ dX at Plab = 2.5 -: 3 .8 GeV/c*

V.Yu. Grishina°, L.A . Kondratyukb, M.

An experiment on a+-meson production in the reac-tion pp -4 daö (1) decaying into ir+rl and K+R0 is inpreparation for the ANKE spectrometer [1] . In thisreport we present the results of our analyses of pos-sible background from nonresonant 7r+77 productionin the reaction pp -+ d7r+71 (2) .A rough estimate of the total cross section for thereaction pp -+ pn7r+77 (3) can be obtained as fol-lows : The ratio of 77/iro production in pp- collisionsis approximately R = a(pp?l)/Q(pp7ro) - 1/15=1/20at 3.4 GeV/c. We assume that a(pnr?7r+) = Rv(pmro7r+) . Taking a(pn7ro7r+) - 4 mb we find thata(pnr77r+) - 200 - 250 /.tb. The probability that thefinal p and n fuse into a deuteron was calculated us-ing the coalescense model and found to be - 0.02.This gives v(d?77r+) - 0.02 - o-(pn7r+?7) ^= 4 ; 5 yb.However, this estimate is rather crude because it doesnot take into account spin-parity conservation argu-ments . As a matter of fact, the final system in reac-tion (2) cannot be in S-wave. Thus, near thresholdthe main contribution comes from the d - (7r+71) P-wave.A more realistic estimates can be obtained from theamplitude which is described by the diagram shownon the left side of Fig.1, where the q- and 7r-mesonsare produced through one-pion exchange . The domi-nant intermediate state are the A(1232) (in the am-plitude 7rN --+ 7rN) and the N*(1535) resonances (inthe amplitude,7rN -+ 77N) .In [2] it was demonstrated that in the case of thereaction pp -+ NO(1232) the pion-exchange ampli-tude is dominant . We analyzed this amplitude inorder to fix the parameters for the ANTr vertex .For a virtual pion in each vertex we introduce aform factor of monopole type with a cutoff parame-ter A, r = 1=1.3 GeV/c. For the AN7r vertex we alsotake into account the so-called barrier-penetrationfactor

F(Ig7rNI) =

IgRI2 +X2

Ig7rNI2 -f K2

which takes into account the dependence of the A7rNcoupling constant on the deviation of the relativepion-nucleon momentum Ig7rNI in the 0-isobar restframe from the resonant value IgRI = 0.227 GeV/c.Using A7rNN = 1 GeV/c and r. = 0 .3 GeV/c weobtain the pp nA++ cross section Orpp-fn0++ -

15 mb at Tiab = 0.8 GeV which is in reasonableagreement with the value of 13.4 mb found in [2] .The 7rN -> r7N S-wave amplitude (which includesalso the N(1535) contribution) was taken as in [3].The result for the nonresonant contribution to thepp --; d7r+77 cross section as a function of the pro-ton laboratory momentum is presented by the dashedcurve 2a on the right side of Fig.l . To demonstratethe sensitivity of our prediction to the choice of thepion cut-off parameter we changed A7rNN from 1

Büscher, Ye.S . Golubevaa and H. Str8her

GeV/c to 1.3 GeV/c and obtained the dashed curve2b . The solid curve shows the ao contribution to thepp --+ d7r+71 cross section which was calculated us-ing the pp -+ daö total cross section from [4] multi-plied by the factor 0.8 (branching ratio for the rr7 de-cay mode of ao) . For the maximum energy at COSYTiab _ 2.6 GeV (plab = 3.41 GeV/c) the total crosssection of the nonresonant 7r+77 production can beestimated as 1 .6 - 3.3 pb while the resonant contri-bution to the pp --> daö (-4 r77r+) cross section atthis energy is predicted to be - 1 Mb. Our calcula-tions ofthe ir+ ,) continuum background gives amuchsmaller cross section as compared with an estimateof [5] . This means that when the events from the re-action pp -+ dir+q are selected, one can expect thata comparatively narrow ao contribution can be sep-arated from the .7r+,n continuum on missing-mass orDalitz-plot distributions.

Figure 1: Left side : diagram describing the nonreso-nant 7r+77 production in reaction (2) ; right side : totalcross sections of reactions (1) (solid curve) and (2)(dashed curves) as functions of plab .

References :

[2]

J. Hundomalj-Gabitzsch et al ., Phys.Rev . C 18(1978) 2666 .

[4] V.Yu. Grishina et al., Eur.Phys.J . A 9 (2000)277.

a

2.5 3 3.5

Pl.n [GeV/c]

M. Büscher et al ., in Proceedings of Workshopon ao Physics with ANKE, ITEP, Moscow, July,2000, Berichte des Forschungszentrums JülichJill-3801, ISSN 0944-2952 (2000) p. 23 .

V.Yu. Grishina et al ., Phys.Lett . B 475 (2000)9.

H.Mfiller, contribution to this annual report andsubmitted to Eur.Phys.J . .

aInstitute for Nuclear Research, 60th October An-niversary Prospect 7A, 117312 Moscow, RussiabInstitute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117259 Moscow, Russia"` Supported by DFG and RFFI .

EY

v 1U"

a

1e'

E

10'aä

Production of aö mesons in the reaction pp -3 daö

The structure of the lightest scalar mesons ao(980)and fo (980) is not yet well understood (see the "noteon scalar mesons" of the particle data group [1] andreferences therein) . In a recent paper [2] the neces-sity of new measurements of ao production and of aobranching ratios for clarifying the ao structure hasbeen emphasized . Such an experiment is presentlyprepared at COSY [3].

p(3.4 GeV/c) + p -> d + K++ XTI a-

,e.aE

j10,a9

,e'

L

.

I W.

I 1 .W 1

0.4

0.45

0.5

0 Ks

0 .98

1

1.02missing mass M dK (GeV)

missing mass M d (GeV)

p(3.4 GeV/c) + p -+ d + k+ +X

E 10'

9

a9 ,e<

,e"

0 0.2 0 .4 0.6 0 .8 0.6 0 .7 0.8 0.9 1missing mass M de (GeV)

missing mass M d(GeV)

Figure 1 : Missing mass distributions for the reac-tions pp -4 dK+X (upper panels) and pp -~ d7r+X(lower panels) calculated at incidence momentum3.4 GeV/c for polar angles 0 <_ 10° and 1.5% mo-mentum resolution . The two arrows in the left handpanels indicate the windows in the MdK and Md,distributions, which are used in the calculation ofthe Md distribution shown in the right hand panels .The dashed histograms indicate the contributionsfrom the reaction pp --+ dao, the dotted histogramsthose of the nonresonant channels pp -+ dK+Ko andpp -+ d7r+rl, respectively. See text for details .

Although in [2] predictions for the reaction pp -+ daöat COSY energies has been given, no attempt hasbeen made to compare the channels with aö produc-tion and subsequent decays, pp -+ daö -3 dK+Koand pp daö -+ d7r+,q, with the nonresonant chan-nels pp -~ dK+K° and pp -> d7r+rl . For the mea-surement of aö production the latter channels mightbe rather disturbing if they are of high intensity. An-other source of background are multipion channels,where two or three pions may have an invariant mass

H. Müller'

31

similar to the 77 mass . In Fig. 1 ROC-model [4] pre-dictions of the cross sections for ao production to-gether with an estimate of the cross sections for thenonresonant and the multipion channels at the high-est COSY energy are given. In these calculations theaö is considered as a usual quark model state withtwo decay channels ao -> K+Ko and aö -~ ?r+rl.The missing mass distributions of two particles areused to select the mass of the third particle definingthus the final channel. Then the signal from the aö islooked for in the missing mass distribution of the d.In case of strangeness production there are no back-ground reactions, while channels with three or fourpions may contribute to the q window in the Md,rdistribution . The difference between the full and thedotted histogram in the lower right panel of Fig. 1 isthe contribution from these pion channels .The main difficulty consists in differentiating be-tween the channels via the ao meson and the chan-nels with nonresonant production, especially in caseofthe channel pp --> dK+K°, where the.missing massMd varies only by about half the assumed width ofthe ao meson. The value of the calculated cross sec-tion for ao production is . closely related to the as-sumption that the ao consists of light quarks . Forthe direct population of the channel pp --} dK+Kothe creation of a dd and a ss pair is necessary.Strange quark production is suppressed and, there-fore, the larger contribution to the final channeldK+Ko comes from an intermediate aä. In case ofthe decay channel, aö -4 ?r+77, the ROC model pre-dicts higher cross sections for the nonresonant chan-nel than for ao production . Therefore, the measure-ments should be carried out with high statistics .References :

[2] V. Y. Grishina et al ., Eur. Phys . J. A 9, 277(2000), nucl-th/0007074 .

C. Caso et al ., Eur. Phys . J. C 3, 1 (l998) .

V. Chernyshev et al ., COSY Proposal #55"Study of ao mesons at ANKE", Jülich(1997), available via http://ikpdl5 .ikp.kfa-juelich.de:8085/doc/Anke .html.

[4] H. Müller, Eur. Phys. J. C (in print), hep-ph/0011350 .

'Institut für Kern- und Hadro-nenphysik, Forschungszentrum Rossendorf, Postfach510119, 01314 Dresden, Germany*Work supported in part by BMBF grants 06DR920and 06DR828/I .

An atomic beam source (ABS) for polarized hydro-gen and deuterium is under development which willbe utilized to feed the storage-cell of the gas targetto be installed at the magnetic spectrometer ANKE.The assembling of the ABS has been completed . Thiscontribution presents the essential constructional el-ements of the ABS complementing an earlier report[1], it gives the results of the first beam studies, andlists the future steps to establish the polarized gastarget at ANKE.

Layout of the ABSThe layout of the ABS is shown in Fig . 1. Due tospace restrictions at the ANKE target area, only avertical installation is possible . The slight tilting byabout 6° may be required in order to avoid sputteringmaterial from the discharge in the dissociator (1) todrizzle into the storage cell (7) . Laboratory test runswill show, whether the inclination is needed . A pow-

The Polarized Internal Gas Target for ANKE - Status and Future Developmentsl

R. Emmerich', R. Engels2 , E. Kitanina3, F. Klehr4 , H. Kleiness , V . Koptev3, P. Kravtsov3 , J . Ley2 ,B. Lorentz, M . Mikirtytchiants*, M. Nekipelov*, V . Nelyubin3, H . Paelz gen . Schieck2,

F . Rathmann' ,§, U . Rindfleisch, J. Sarkadis , H. Seyfarth, E. Steffens', A. Vassiliev3 , K . Zwo115

1000 mm

500

0

Figure 1 : The atomic beam source for ANKE (boldface numbers in the text refer to those in the figure) .

erful pumping system provides the necessary vacuain the chambers I to IV. Two Pfeiffer TPH2200 tur-bopumps (combined H2 pumpingspeed 5600 2/s) aremounted on chamber I, each followed by a PfeifferTMH260 turbopump. The two TMH260 are backedby a common third-stage TMH260 and finally bytwo Pfeiffer MD8 diaphragm pumps. The smallergas load in chamber II is pumped by a single setof TPH2200-TMH260-MD8. Two Leybold Coolvac3000 cryopumps (each of 3000 i/s H2 pumpingspeed

and of 28 bane H2 capacity at 10'' mbar) are in-stalled at the chambers III and IV. This pumpingsystem (14400 t/s in total) at a primary H2 inlet flowof 1.5 mbari/s yields pressures of about 10-'4 , 10 -',10-7 , and 5 - 10`8 mbar in chamber I, II, III, andIV, respectively .The plasma discharge in the dissociator (1) is main-tained by inductive coupling of 13.56 MHz from arf-power supply and an adapter network . The innerdischarge tube (Duran 8330 glass of 14 mm outerdiameter and 1 .5 mm wall thickness) is cooled by acoaxial water flow . The nozzle at the lower end ofthe dissociator can be cooled down to about 40 Kby a Leybold RGS120 1-stage cryocooler (2) via aflexible connection by either a Cu heat bridge or aNe heat pipe . The details at the lower end of thedissociator are shown in Fig . 2. The transition fromthe cold nozzle to the outer dissociator tube avoidsany force on the discharge glass tube . Thermal con-tact to the lower part of the discharge tube is pro-vided by a modified sliding rf connector . This spe-cial construction allows to extract and reinstall theglass tubes and the rf-generating elements withoutdisassembling of the heat bridge and nozzle . The

32

Duran 8330

Teflon spacer

Teflon ringsliding heat connectorheat insulator (SS)groove for heatercoppernozzle (Al 99 .5)baffle I-IIskimmer

collimatorIst magnet

baffle 11-111

Figure 2 : The region between the lower end of thedissociator and the first sextupole magnet (diameterof nozzle, skimmer, and collimator : 2, 3, and 8 mm)respectively ; distance from skimmer entrance to firstmagnet 35 mm) . Components not labeled are madefrom stainless steel (SS) .

design considerations for the set o£ permanent sex-tupole magnets (two groups, 3 and 5) and the resultsof the field distribution measurements are describedin a recent publicationr [2] . To protect the magnetsfrom hydrogen, they were enclosed in stainless steelcans with inner tubes of 0 .2 mm thickness in orderto maximize the free magnet apertures .Both rf transition units to provide purely polarizedH atoms with ml = ±1/2 have been designed andbuilt at Universitat Erlangen [3] . The medium-field

unit (4) has been installed, tested, and is ready foroperation . The weak- and strong-field unit (6) willbe installed as soon as the Lamb-shift polarimeter isavailable for beam-polarization studies .

Results of first ABS-beam studiesWith a crossed-beam quadrupole mass spectrometerdegrees of dissociation of the beam have been mea-sured to be about 70% for a pure H2 inlet flow of 1.0mbar /s . The ABS operation parameters have beendetermined by maximizing the atomic beam inten-sity into a compression tube . Its dimensions (10 mmdiameter and 100 mm length) and its position (tubeentrance 300 mm behind the last sextupole magnet)are those of the future storage-cell feeding tube . Theresulting values of 1 .3 mbari/s for the H2 inlet flowand 300 W for the rf power are close to those mea-sured at other sources [4, 5, 6] of comparable geom-etry and aiming at high beam intensity, e.g . to feeda storage cell

[4, 5] .With a fixed distance of 35 mm between skimmerentrance and first magnet, the optimum nozzle-to-skimmer distance was found to be 14.8 mm . Withthese values the H beam intensity into the com-pression tube has been measured as function ofthe temperature at the base of the nozzle . The re-sults are shown in Fig . 3. The highest intensity of

$I q [110P pol. H atoms/s]

o

pINTDC

7;

3-

2-

. . . . . . .

':

.~

. ..

.

.

. . . . . ."

!'ANKE-ASS wilhi'l>Omchnixturo"40 .0

"

0 . :ANKE:ABSwfrhout0=; .

_.°°

0 0

4!

00 0E ..

o

"0 50

100

15oT[K]

Figure 3 : fl-beam intensity into the compression tubeas function of the nozzle temperature compared withthe values given for other sources in similar geo-metry (for PINTEX, HERMES, LMU Miinchen seerefs . [4], [5], and [6], respectively) .

(6 .4 ± 0 .3) - 1016 is close to the best values publishedfor other sources. However, it is obtained with a lowerinput flux . Measurements of the temperature distri-bution along the nozzle are underway . As suggestedby Fig. 3, the beam intensity will be measured atlower nozzle temperatures possibly after installationof a 2-stage coldhead .

Future developmentsA Lamb-shift polarimeter has been designed, built,and tested with unpolarized gas [7] at the Universitätzu K61n [8]. It has been transferred to Jülich and itfirst will be used to study the nuclear polarizationof the atomic beam, thus enabling a fine tuning ofthe rf transition units, and later to investigate thepolarization of the gas in the storage cell . The slow

33

control and interlock system is extended to controlthe various polarimeter components as well .COSY-beam studies have been started with use ofsimple rectangular and elliptical diaphragms of 10mm vertical and 30 mm horizontal width placed atthe ANKE-target position . The first results demon-strate that additional beam-position monitors andvertical beam steerers near the ANKE target are re-quired .A new large target chamber is under developmentwhich will allow to extend the beam studies withstorage-cell prototypes . The chamber will also housetailored beam- position monitors near the storage cellof the polarized gas target .The nuclear polarization of the target gas in a stor-age cell can be determined by measuring polariza-tion observables in the interaction of the target nu-clei with the accelerator-beam projectiles, if polar-ization data exist. Otherwise a suitable polarimeterhas to be used to analyze a subsample of the gas ex-tracted from the target cell . However, such polarime-ters (like the Lamb-shift polarimeter) are suited tomeasure the nuclear polarization of atoms and do notdirectly yield information on the nuclear polarizationof recombined molecules in the target gas. In orderto continue and to complete first measurements onthe nuclear polarization in recombined H2 and D2molecules at NIKHEF [9] and IUCF [10], a collabo-ration project with the PNPI has been started in theframework of the International Science and Technol-ogy Center (ISTC) initiative [11] .1The work was supported by BMBF (contracts RUS 99/686and 06 ER 831), by DFG (contract 436 RUS 113/430), by FZJülich (FFE, contract 41149451), and by the Russian Ministryof Sciences .2Universitiit zu Köln, 50937 Köln, Germany.3PNPI, 188350 Gatchina, Russia.4Zentralabteilung Technologie, FZ Jülich .5Zentrallabor für Elektronik, FZ Jülich .6Universitiit Erlangen, 91058 Erlangen, Germany.#PhD-Student from PNPI, 188350 Gatchina, Russia.§Now : IKP, FZ Jülich, 52425 Jülich, Germany.

References:R. Baldauf et al ., Annual Report IKP andCOSY 1999, report Jiil-3744 (Berichte des FZJülich, 2000), p. 36 .A. Vassiliev et al ., Rev . Sci . Instr . 71, 3331(2000) .S . Lorenz, diploma thesis, Universität Erlangen(1999) .F. Rathmann et al ., AIP Conf. Proc . 421, 89(1998) .J. Stewart et al ., as ref [4], p. 69 .R. Hertenberger et al ., Proc . Int. Workshop onPolarized Sources and Targets, Erlangen . Ed . A.Gute, S. Lorenz, E. Steffens (Universität Erlan-gen, 1999), p.52.R. Engels et al ., as ref. [1], p. 39 .R. Engels, PhD work, Universität zu Köln.J.F.J . van den Brand et al ., Phys . Rev. Lett . 78,1235 (1996) .

10] T. Wise et al ., publication in preparation .111] ISTC project No. 1861 (2000) .

[2]

[3]

[4]

[6i

During January/February 2000 the target tests atITEP were continued . Anew modified heat-exchangehead, a new membrane between the isolating vacuumvolume and the first vacuum chamber and a full-scale temperature measurement system were tested .Five test runs with cooling by liquid helium wereperformed during this period . The obtained resultscan be summarized as follows:

Status of the pellet-target preparation for ANKE*

V. Balanutsaa, W. Borgs, A. Boukharova, M. Biischer, V. Chernetskya,V . Chernysheva, M. Chumakova, A. Dmitrieva, P. Fedoretsa

. The expected temperature of the heat-exchange head (from 10 K to 25 K) wasachieved . This is a prerequisite for hydrogen-gas condensation .

" A jet of liquid hydrogen from the nozzle to thetriple-point chamber was observed .

" The low pumping capacity of the vacuum sys-tem at ITEP did not allow for long-term oper-ation (more than several minutes) with gener-ation of liquid hydrogen jets .

In March 2000, the target equipment was trans-ported from ITEP to FZJ and the preparation forvacuum tests ofthe target cryostat were started. Thiswork includes development, production and buyingof equipment for a completely new cryogenic systemaround the target . Then this system was assembledand tested and cryogenic tests of the target werestarted. The most important and long-term activitiesat FZJ include the development and test of liquid he-lium and nitrogen supply systems as well as controland diagnostic facilities . The target may partially beredesigned during the test process.The assembling of the target infrastructure andsupply systems at IKP was performed during twomonths (April and May) . As result of this successfulactivity, the first tests (test run #1) of the target atIKP were already started in June 2000 . During thistest run, long-term operation of all target systemswas established. A vacuum in the isolating volumeand the main vacuum chamber of the cryostat ata level of 10-7 mbar was achieved . It was confirmedthat the present vacuum system provides a stable op-eration at a pressure of 100 mbar in the triple-pointchamber.The following target tests (runs #2-4) took a placeat IKP in November 2000 . During the preparation ofthis test run the following technical tasks have beensolved :

" The vacuum system has been modified ." The dumping cryostat was prepared for assem-

bling with the target cryostat and tested ." Four new hydrogen filters from baked bronce

and titanium oxide were produced .

" The flow-resistance characteristics of the hy-drogen filters were measured .

" The old hydrogen filter was removed from thecryostat and a new one was installed.

" The liquid helium supply system was equippedwith new valves and lines for the long- termoperation.

" The hydrogen system was modified with newsupply lines and pressure-control valves .

The tests concentrated on the cooling andtemperature-stabilization systems, and study of con-ditions (temperature, pressure, gas fluxes) requiredfor the stable liquid hydrogen jet production in thetriple-point chamber. The results can be summarizedas follows:

" The pellet target is assembled at IKP of FZJfor the permanent tests.

" The cooling systems can operate reliably dur-ing long time (more than 50 hours) .

" The total requested cooling time (time of tem-perature stabilization) of the target cryostat isabout 20 hours.

" The target supply systems can be operatedduring at least 4 days .

" The supply systems can provide pressures andgas flows with accuracies of about 1%.

" Short lived jets and single H2 droplets were ob-served during the target tests. This means thatthe necessary conditions for hydrogen-jet pro-duction can be established.

a Institute for Theoretical and Experimental Physics,Moscow, Russia .*Work supported by grants : RFF199-02-18179a, RFF199-02-04034DFG,INTAS98-500, DFG-443RUS-113,WTZ RUS 99/684 .

The proposed photon detector [1] for ANKE hasto be operated in the magnetic environment of thestray field of a 1.6 T dipole . The field strength atthe positions of the single modules is B <_ 0.2 T.To exploit the fast timing of the detector materialPbW04 [2], it is necessary to use photomultipliersfor readout rather than slow conventional photo-diodes or avalanche photodiodes (APD) . Using anAPD one can reach a time resolution of ,:, 1 ns, butits noise in combination with the low light outputof PbW04 makes it unsuitable for this application.While photodiodes are insensitive to external mag-netic fields, only special fine-mesh phototubes can beoperated in such an evironment . These are insensi-tive to magnetic fields parallel to the multiplier axis(up to B< 1 T), but have to be shielded against thetransversal field component. Since the photon detec-tor is of spherical shape, all directions of the mag-netic field are equally important with respect to themultiplier axis .The only commercially available model of this fine-mesh type (Hamamatsu 115505), has been tested in-tensively. Figure 1 shows some test results for theunshielded tube . As expected, with the field parallelto the multiplier axis almost no effect on the ampli-fication is seen, but using a perpendicular field theoutput alreadv drops down at 0.02 T.

Test of the HAMAMATSU 115505 fine-mesh phototube in magnetic fields

Figure 1: The behaviour of an unshielded 115505-tubewithin a magnetic field . The relative angles betweenthe magnetic field and the tube axis are 0° (closedsymbols) and 90' (open symbols), respectively.

In fig . 2 the same situation is shown using a shieldingtube of soft iron (wall thicknesses 1 mm and 2 mm) :the undisturbed range extends to at least 0.12 T.From this it is concluded that the existing stray fieldat ANKE can be handled with a shielding thicknessof 3 mm.These studies have been performed in a static mag-netic field . During the experiment the multipliershave to withstand the ramping between two accel-erator cycles and the amplification has to recoverto the same value in all data taking cycles . This

V.Hejny, R.Novotnyl, K.R8merl

35

00 200 400 600 800 1000 1200

magnetic field [Gauss]

Figure 2: Shielded 115505-tube (Imm/2mm soft iron)in a magnetic field up to 0.12 T. The magnetic fieldis oriented perpendicular to the multiplier axis .

aö 1aao

goo

800

700

References

-1950v -r;

§L0'6 . I. 0.s.,-4'--0-- 1mmshielding+ ' 2mmshieldln

600r-08 :50

09:00

09:10time

Figure 3: The behaviour of the shielded 115505-tube(3mm soft iron) at the designated position under ex-perimental conditions at ANKE. The pulse height isplotted as a function of time . While the two peaksoriginate from the ramping ofthe magnet, the ampli-fication before and after each ramping is essentiallyunchanged .

has been checked during an ANKE beam time inSeptember 2000 . The phototubes were illuminatedwith LEDs and positioned in front of the dipole mag-net. As shown in fig. 3 the ramping (i .e . the change ofthe magnetic field during acceleration of the COSYbeam) has some effect on the pulse height of the mul-tiplier, but the output within a beam cycle (flat top)is stable andhas the same value before and after eachacceleration . This means that the 115505 meets thedemands for the proposed photon detector at ANKE.

[1] M. Bfischer et al ., COSY Proposal #83: A pho-ton detector for COSY, November 2000 .

[2] V. Hejny et al ., PbW04 as a scintillator mate-rial for a photon detector at ANKE/COSY, IKPAnnual Report, 1999 .

1 Il. Physikalisches Institut, Universität Gießen

Deuteron Breakup pd -+ pnp and Short-Range NN-Interaction

Yu.N. Uzikova,t,V.I . Komarovb, F. Rathmann, H. Seyfarth

The short-range structure of the lightest nuclei isrelated to fundamental problems of the theory ofstrong interactions . At present, the main task con-sists of clear experimental observation of this struc-ture . In the framework of the impulse approximation(IA) the available experimental data on spin aver-aged cross section of the deuteron disintegration ininclusive experiments d*+ p -+ p(0°)X, d +12 C -+p(0°)X are compatible with the realistic wave func-tions of the deuteron (from, e.g . the Paris or Bonnpotentials) only at low internal momenta of the nu-cleons inside the deuteron q < 0.3 GeV/c. At highermomenta q a systematic deviation from the IA isobserved . This disagreement is very strong for thetensor analyzing power T20 of these reactions . A pos-sible explanation of such a behaviour is the presenceof a NN*-components in the deuteron [1]. However,other interpretations based on the virtual pion ex-change are available too. The experimental data onexclusive experiments p -i- d -+ p -I- n -{- p show a sim-ilar deviation from the IA, which can be explainedby rescattering in the final state and excitation ofthe A-isobar [2] . An important role of the final-state interaction and excitation of the nucleon iso-bars in these reactions leads to large screening ef-fects in the corresponding observables . At present, acorrect treatment of these screening effects is a non-trivial problem for the theory . It can be seen from theanalysis of the backward elastic pd-scattering in theframework of the coherent sumof the one nucleon ex-change (ONE), A- isobar excitation (A), pN singlescattering (SS) . The ONE+A+SS model describesqualitatively the spin-averaged cross sections at ini-tial energies Ty = 0.2 -1.5 GeV and scattering angle0,n, . = 180° but does not solve the longstanding T20-problem [3] at Tp > 0.4 GeV .Making use of the conditions minimizing the screen-ing effects [4], we have proposed [5] to study thedeuteron breakup p + d -4 (np)s + p and p -i- d -~(pp), -f- n with formation of the singlet (NN),,-pairin kinematics of the backward (quasi)elastic pd-scattering . An analysis ofthe reaction p+d--+ .(pp)s-I-n, performed in the framework of the ONE+O+SSmodel, shows two main features : i) Compared to theONE mechanism the contribution to the cross sectionwith A-excitation is diminished by an isotopic-spinfactor 1/9 and the suppression takes place for severaldiagrams including, in particular, the N*-excitation.ii) For the requested small relative momentum in thefinal pp-pair (k < 50 MeV/c), the pp-scattering am-plitudes in the states with nonzero orbital momentaare strongly suppressed . As a result, a node of thehalf-off-shell Pp(1So)-amplitude t(q, k), predicted bymany realistic NN-interaction potentials at q - 0 .4GeV/c, can be visible in the observables. Rescatter-ing in the initial and final states, taken into accountfor the dominant ONE-mechanism in the eikonal ver-

N10

References:

T,, (GeV)Figure 1 : Laboratory cross section (a) and TZo

(b) for the reaction p -I- d --* (pp)(0° ) -I- n(180°)at a relative pp-pair energy Epp = 3 MeV cal-culated for different mechanisms : ONE (dashed),ONE with rescattering (dotted), coherent sum ofthe A+SS+ONE with rescattering (solid) . In (a)the SS- and A-contributions are shown separatelyby dashed-dotted curves . The figure is from ref. [7].

sion of the DWBA method [6], does not change themainfeatures of the cross section as canbe seen fromFig.1(a) . In particular, the node of the half-off-shellpp(1So)-scattering amplitude results in a dip in thecross section. Due to rescattering and interferencewith A and SS-mechanisms there is a strong bumpin T2c at the position of this node (Fig.1(b)) . Theparameter Cy,y shows similar features [7] .

'Kazakh State University, Almaty, Kazakhstan;delegated to Joint Institute for Nuclear Research,Dubna, Russia .°Joint Institute for Nuclear Research, Dubna,Russia .(Supported by BMBF (WTZ grant KAZ 99/001) .

[1] A.P. Kobushkin, Phys.Lett . B421, 53 (1998) .[2] S .L . Belostotski, O.G . Grebenyuk, L.G. Kudin

et al ., Phys.Rev . C56, 50 (1997) .[3] Yu.N . Uzikov, Part.Nucl .Phys. 29, 583 (1998)-[4] V. Abazov et al ., COSY Exp. Proposal No.20.3

(1999), spokesperson V. Komarov .[5] 0. Imambekov,Yu.N. Uzikov, Sov.J.Nucl.Phys-

52, 862 (1990) ; A.V . Smirnov andYu .N . Uzikov,Phys.At . 61, 361 (1998) .

[6] L.D . Blokhintsev, A.V . Lado, Yu.N . Uzikov,Nucl.Phys. A597, 487 (1996) .

[7) Yu .N.Uzikov, Preprint JINR E2-2000-149; nucl-th/0006067 .

Near-threshold w and 4 production in pp and pd collisions and polarized intrinsic strangeness ofthe nucleon*

and

M. Büscher, V. Yu . Grishina', L.A . Kondr'tyukb, and H. Str6her

It is well known (see e.g . [1] and references therein)that the ratio of the 0/w yields where the initial andother final hadrons do not contain strange quarks,is a particularly sensitive probe of the OZI rule .At the standard deviation 8 = 0 - Bi = 3.7° fromthe ideal mixing angle Bi = 35.3° degrees we haveR/f = 4.2 x 10-3 , where f is the ratio of the phasespace factors. However, the existing experimentaldata show an apparent excess of R/f above the stan-dard value.In Ref. [1] the large excess of R in pp and pp col-lisions over the prediction by the OZI rule was ex-plained as an effect of intrinsic ss component in thenucleon wave function. Moreover Ellis et al . [2] ar-gued that the dominant contribution comes from the3 Po configuration with the total ss spin negativelypolarized with respect to the nucleon spin . Withingthe framework of this polarized nuclear strangeness(PNS) modelhe 0 production in NN collisions depends on the spinof the initial state: it is more abundant in Si = 1state, than in Si = 0 state. To test this prediction,the reaction pp --> ppo using polarized beam and po-larized target, was discussed in Refs .[3, 4] . Here weconsider another possibility to check the PNS modelin the near-threshold w and 0 production in pp andpn collisions using an unpolarized beam and unpo-larized target .Let us consider the reactions pp -+ ppw (a), pn -+ dw(b), pp -+ ppo (c) and pn -+ do (d) near the cor-responding thresholds (i.e . at the same c.m . energyrelease Q) . It is essential that the isospin of the ini-tial and final states is fixed for all these reactions :Ii = If = 1 for reactions a) and c) and Ii = If = 0for b) and d) . At Q below 50 - 60 MeV one expectsthe dominant role of the S-wave contributions to thefinal states and, therefore, the initial spin states ofthe reactions (a)-(d) will be fixed by spin and parityconservation arguments : Si = 1 for reactions (a) and(c) and Si = 0 for (b) and (d) . It means that thecross section ratios

(measured at the same Q) will contain the informa-tion equivalent to polarization experiments. Accord-ing to the PNS model the relative production of 0is expected to be more pronounced in the reactionpp -+ ppV than in pn -+ dV, i.e. R =Rca/Rdb » 1.Hence, comparing the experimental ratio of the 0/wyields in pp and pn collisions Rexp = Re,,p/Rdbwith theoretical predictions, based on PNS modelRtheor » 1, will allow us to obtain new informationon the nature of the OZI rule violation.

37

According to existing experimental data on w and 0production in pp collisions Rca = (49 f 26) x 10-3(See [5]) . There are no data on w and productionin the pn -3 dM reaction . Using the two-step modelwhich is described by triangle graphs with r-, p- andw-meson exchanges the pn --} dM cross section wascalculated in [6] close to thresholdor M = w, 0. The predicted cross section of the re-action pn -+ dw is found to be significantly largerthan the the cross section of the reaction pp -+ ppwat Q < 50 MeV. The same is expected in the caseof 0 production . The ratio Rdb was found to beRdb = (34 f 10) x 10-3 . According to results ofmodel calculations presented in [7] one can obtainRdb = (9 - 24) x 10-3 at Q = 30 MeV.In comparison with the earlier measurements thestudy of w- and 0-mesons production in the reac-tions (a-c) at COSY has the following advantages :i) Since all the reactions will be studied at the sameQ (c.m. energy release) the OZI violation parametercan be determined through the cross section ratioswithout introducing any phase-space corrections.ii) At ANKE the 0-meson production can be de-tected via its decay into a K+K--pair .iii) The deuteron in the final state is preferable toproton-neutron because of the large two-body phasespace near threshold and because of the higher de-tection efficiency.Note that the experiments on the w- and 0-mesonproduction in the reactions (b) and (d) at ANKE areforseen by the COSY proposal No.75 [8] and analysisof the first data on the reaction (b) at Tp = 2 GeVis already in progress .References:

[2]

J . Ellis et al., Nucl.Phys. A673 (2000) 256.

J. Ellis et al ., Phys.Lett . B353 (1995) 319.

M. Sapozhnikov et al ., COSY Letter of IntentNo.35 (1995) .

[4] A.I . Titov et al ., Eur.Phys.J . A7 (2000) 543.

F. Hibou et al., Phys . Rev. Lett . 83 (1999) 492.

V.Yu. Grishina et al ., YaF 63 (2000) 1913 .

K. Nakayama et al., Phys.Rev.C63 (2001)015201 .

[8] M. Büscher, R. Schleichert et al ., COSY Pro-posal No.75 (1998) .

'Institute for Nuclear Research, 60th October An-niversary Prospect 7A, 117312 Moscow, RussiabInstitute of Theoretical and Experimental Physics,B . Cheremushkinskaya 25, 117259 Moscow, Russia* Supported by DFG and RFFI.

Rca = U(PP -+ PPO)/Q(PP -3 PPw) ( 1) [5]

Rdb = v(pn -+ dO)/o-(pn -4 dw) (2)[6]

and width

Studying the w properties in pA collisions via the w-+7roy decay

The modification of the w-meson properties in nu-clear matter has become a challenging subject indilepton physics from 7r-A, pA and AA collisions .Here the dilepton (e+e- ) radiation from w's propa-gating in finite density nuclear matter is directly pro-portional to the w spectral function which becomesdistorted in the medium due to the interactions withnucleons . w-production in pA collisions can be con-sidered as ameans to study the w-properties at nor-mal nuclear density under rather well controlled con-ditions.The in-medium w-spectral function can also be mea-sured directly by the decay w-40y. The advantageof the w--~-7roy mode is due to an isolation of thew-signal, while the dileptonic mode always has tofight with a background from p° decays which areas well produced in pA collisions with compatibleprobability. The calculations (see [1] for details andreferences) are performed within the transport modelused before for po and Kt studies [2] by taking intoaccount both the direct pN-+wpN, pN-->wpN.7r andsecondary pN-47rNN, irN-3wN production mecha-nisms as well as wN elastic and inelastic interactionsin the target nucleus and accounting for 7r'N rescat-tering . Here the w propagation is described by theHamilton's equation of motion and its decay to 0rby Monte Carlo according to the survival probabilityPW(t-to)=exp(-FV(t-to)) in the rest frame of themeson created at time to, while I'V=8.4 MeV denotesthe inverse w-life time in the vacuum.To examine the feasibility of a direct detectionof in-medium modifications via the 7roy invariantmass spectrum, calculations for p+Cu collisions at2.4 GeV are performed by introducing a real andimaginary part of the w-potential

V. Hejny, W. Cassing', A. Sibirtsev, H. Str6her

F

in the t-p-approximation . Here Mo and Fo are thebare mass and width of the w-meson in vacuum whilep is the local baryon density and po=0.16 fm-3 . Theparameter Q=-0 .16 was adopted from various mod-els cited in [1]. The predictions for the w-meson col-lisional width F,ott at density po range from 20 to 50MeV.These estimates are based on the local density ap-proximation and neglect a momentum dependenceof the w-potential. Since the model uncertainties arequite substantial [3, 4, 5] this situation needs exper-imental clarification .The solid histograms in Fig. 1 show the Troy invari-ant mass spectra from p+Cu collisions at 2.4 GeV

38

References

Figure 1: The Troy invariant mass spectra from p+Cucollisions at 2.4 GeV calculated for F,,,11=20 and50 MeV (open histograms) . The hatched histogramsindicate the contributions from w-mesons, that decayat finite density and include 7ro rescattering, whilethe solid curves show the w-spectral function in vac-uum for comparison .

calculated with F,,ott=20 MeV (upper part) andF,,,,=50 MeV (lower part) while employing the po-tential (1) . The results (including an `experimental`resolution of 10 MeV) indicate asubstantial enhance-ment of the low mass 7ro-y spectra due to the contri-bution from w-mesons decaying inside the nucleuswhile feeling the attractive potential (1) .These experiments might be carried out at COSYwith a dedicated photon detector looking for the3y invariant mass distribution and gating on eventswhere 2 -I's yield the invariant mass o£ a gyro. This pro-gram is complementary to dilepton studies in thesereactions, that will be carried out with HADES de-tector at GSI Darmstadt [6].

[1] A. Sibirtsev et al ., Phys . Lett . B 483 (2000) 405.

[2] A. Sibirtsev and W. Cassing, Nucl . Phys. A 641(1998) 476., Nucl . Phys . A 629 (1998) 717.

[3] W. Cassing and E.L . Bratkovskaya, Phys. Rep.308 (1996) 65 .

[4] G.E . Brown et al ., Acta Phys . Pol. B 29 (1998)2309 .

[5] G.I . Lykasov et al., Eur. Phys . J. A 6 (1999) 71 .

[6] J. Friese et al. (HADES Collaboration), Prog.Part . Nucl. Phys . 42 (1999) 235 .

'Institut für Theoretische Physik, UniversitätGiessen, D-35392 Giessen, Germany

RE- = M0 ,8 P (1)2Mo Po

2Mo Fo+F~ottpo

(2)

Medium effects in the production and 7ro7 decay of w-mesons in pA collisions in the GeV region*

Ye.S . Golubeva°' , L.A . Kondratyuk6 , M. Biischer, W. Cassing°, V. Hejny and H. Ströher

The question about modifications of the w-mesonproperties in the nuclear medium has received a vividattention during the last years (see [l, 2]) . A mesonor baryon resonance produced in hA or AA collisionscan decay outside or inside the target nucleus. Cor-respondingly, the invariant-mass distribution of thedecay products for each resonance contains two com-ponents . The first component is described by a Breit-Wigner resonance with vacuum values for the massMO and width ro. The second component is stronglydistorted by the nuclear medium due to collisionalbroadening Ar and a possible mass shift AM, where,in first approximation, Ar and AM are proportionalto the nuclear density. In principle, medium modifi-cations of w mesons can be detected directly mea-suring the dilepton invariant mass spectra in hA andAA collisions . The advantages of this method arerelated to the fact that the dilepton mass spectraare almost undistorted by the final state interaction.However the w-signal in the dilepton mode is weak(BR(w -> e+e) = 7.1 x 10-5 and is always accom-panied by a comparatively large background from podecays . From this pöint of view it is useful to con-sider also the w -~ Tr oy decay which has a branch-ing ratio of about 3 orders of magnitude higher (see[3, 4]) . As it was shown in Ref. [4] the effect of the wmass shift in 7ro-y invariant mass distribution can beseparated from the background which is related toZON rescattering . Here we consider additional crite-ria which might help to separate the w --* 1ro-y signalin pA collisions at GeV energies from other sourcesof background .The yields of w-mesons in the reaction pA -+ wX at2 .4 GeVwere calculated within the framework of theIntranuclear Cascade Model (INC). The propagationof the w-resonance in nuclear medium (as well as itsmass shift and collisional broadening) is describedhere in the same way as in Ref. [2] where the INCmodel was used for the analysis of medium effects inthe production of w's in pion-nucleus reactions .In Figs . 1 and 2 we present the tr oy invariant massdistributions for p+Pb and p+C, respectively. Fig.1a) and 2a) show the invariant mass distributionswhen medium effects are not taken into account andall the distortion of the M(vo'y) spectrum from wdecay is caused by 0 rescattering. Figs . 1b)-lc) and2b)-2c) demonstrate the 7roy invariant mass spec-trum when only collisional broadening Ar (b) andboth medium effects Ar+A.M (c) are taken into ac-count. The hatched areas in Figs . la)-lc)and 2a)-2c)show the events with rescattered pions. The dottedhistograms in Figs . 1a)-1c) and 2a)-2c) describe theevents with w's decaying outside, while the dashedones correspond to w's decaying inside nucleus withtheir rescattering switched off. The different contri-butions are compared in Figs . 1d) and 2d) where thehistograms correspond to the calculations without

39

c

10

10

Figure 1: The 7r°y invariant mass distriutions inp + Pb collisions at 2.4 GeV. The meanings of thecurves on the diagrams a),b),c) and d) are explainedin the main text .

cä 10

10

c 10

.a

ß

10

10

p+Pb, Tp=2.4 GeV

0.5 0.6 0.7 0.8 0.90.5 0.6 0.7 0.8 0.9

M(1r°y),GeV M(noy),GeV

p+C, Tp=2.4 GeV

0.5 0.6 0.7 0.8 0.90.5 0.6 0.7 0.8 0.9

M(noy),GeV M(n°y),GeV

ä .1

Figure 2: Same as in Fig. 1 for p+C collisions at 2.4GeV.

a b

ON/-,r c d

medium effects (dashed), with collisional broadeningAI' ,-£ 0 but wihout mass shift AM = 0 (dotted)and with collisional broadening DI' ,-~ 0 and massshift CAM 0 0 (solid) (treated in the same way asin Ref. [2]) . In the region M(7ro-y) = 0.65-0.75 GeVthere is a significant enhancement in the spectrumdue to medium effects (solid histograms) relative tothe vacuum w decays (dashed histogram) . This is inagreement with the results of previous calculations[2]- [4].Such an experiment might be carried out at COSYproton accelerator (Mlich) using a photon detec-tor to look for the 37 invariant mass distributionand selecting 2y in the mass region of 7ro. How-ever in the mass region M(7roy) = 0.65-0.75 GeVthere might also be essential 'background' from fourphoton final states (e.g. decay products from 20,r17ro etc.) when one photon is missing due to the fi-nite geometrical acceptance of the detector . Thereare also other sources of background : One of themost important source of three photons may berelated to the reactions pp --+ pA}(p-y) x0 (2y) andpN -> p00(ny)7ro(2y) . This means that an addi-tional criterion how to select the events which corre-spond to w decay inside the nucleus from backgroundis quite important.It is possible to exploit, for example, kinematical con-ditions. If an w-meson is produced not far from thethreshold it should have comparatively small trans-verse momentum PT in the lab. system. In this casewe would expect that the 7r o and y from w decay willbe strongly correlated in their transverse momentawhile 7roy from the background will not have such acorrelation .

aL

10.z

z10 -,

10-z

2.4 GeV

Pb

¬ 1 .9 GeV

Pb

7-- _

2.4 Gey,,----L,

c 1 .9 GeV

0 100 200 300 0 100 200 30000C0)-W),deg . *0H(Y),deg.

Figure 3: The distributions in azimuthal angle 0 =Oro - O.y . The meanings of the histograms are ex-plained in the main text .

To show this correlation in the case of w decay insidenucleus we present in Fig. 3 the distributions of theazimuthal angle between two planes 0 = 0,ro -where one plane is formed by the initial proton mo-

40

mentum and the 7ro momentum (Po n pno) and thesecond one is formed by the initial proton momen-tum and the y momentum (po n p7 ) . The solid his-tograms in Fig. 3 describe the distributions dN/do

from p+Pb (upper) and p+C (lower) collisions atTp = 2.4 GeV (left) and 1 .9 GeV (right)for w decay-ing inside . The hatched histograms which describethe events with rescattered pions are completely flatand do not show any correlation between 7r o and 7.At the same time the solid histograms have distinc-tive maxima at 0 = 180° which correspond to cor-related 7ro and y from w decay. The width of thedistribution dN/do depends on the w-meson trans-verse momentum PT . Therefore it becomes narrowerwith decreasing initial energy and very close to thethreshold it would depend mainly on the Fermi mo-tion of target nucleons and effects of w rescattering .Those effects are smaller for carbon than for lead(compare upper and lower solid histograms in Fig. 3) .Nevertheless the azimuthal correlation remains quitepronounced also in Pb even at 2.4 GeV.We also investigated how different kinematical cutscan increase the signal-to-background ratio . The in-medium modifications are found to be most pro-nounced for the cutsn the total and transversal momentum of 7r o"y sys-tem Ptot < 0.5 GeV/c, PT _< 0.2 GeV/c and theazimuthal angle 0 = ¢,ro - ¢.y = 180 f 30°. For ex-ample the ratio

R = N(M(7ro, y) = 0.6 - 0.75 GeV)

(1)N(M(7ro, y) > 0.75 GeV)

calculated for Pb (C) without cuts changes from0.029 (0.008) when medium effects are absent to0.128 (0.059) when both medium effects, collisionalbroadening and mass shift, are included . The calcu-lations with cuts yield, respectively, the ratio R =0.033 (0.020) whithout medium effects and 0.401(0.183) with collisional broadening DI' 54 0 and massshift LAM =A 0 included . We thus conclude that thestudy of medium effects for w in 7roy decay mode inpA collisions in the near threshold region looks to bequite promising .References:

W. Cassing and E. L. Bratkovskaya, Phys-Rep .308, (1998) 65 .

[2] Ye. Golubeva, L. A. Kondratyuk, W. Cassing,Nucl. Phys . A 625, (1997) 832 .Ye.S . Golubeva, A.S . Iljinov, and L.A . Kon-dratyuk, Yad.Phys. 59 (1996) 1891 .

[4]

A. Sibirtsev, V. Hejny, H. Str8her andW. Cass-ing, Phys . Lett ., B 483, (2000) 405 .

aInstitute for Nuclear Research, 60th October An-niversary Prospect 7A, 117312 Moscow, RussiabInstitute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117259 Moscow, Russia'Institute for Theoretical Physics, University ofGiessen, D-35392 Giessen, Germany* Supported by DFG and RFFI.

ao(980) - fo(980) mixing and isospin violation in the reactions pN -+ aod, pd -+ ao 3He/3H anddd -4 ao 'He*

1 . Reactions (a) and (b)

V.Yu. Grishina a, L.A . Kondratyukb, M. Büscher and H. Str6her

As it was suggested long ago in Ref. [1], the dynam-ical interaction of the ao(980) and fo (980) with thenearby KK thresholds can give rise to a significantao (980) - fo (980) mixing . Different aspects ofmixingdymanics and possibilities to measure this effect werediscussed in refs . [2, 3, 4, 5] . Furthermore, recentlyit was suggested in [6] that the new data from theWA102 collaboration at CERN [7] on the central pro-duction of fo and ao in the reaction pp a pSXpf giveevidence that the fo - ao mixing intensity is quitesignificant and is as large as 11 2 = 8 f 3% . Herewe would like to discuss possible tests of the mix-ing in the reactions pp -+ aö d (a), pn -+ a00 d (b),pd -~ ao 3H (c), pd -+ a00 'He (d) and dd -+ a0 4He(e) which all can be studied at COSY. The ao-mesoncan decay into 7rr7 or KR. In all the cases consideredhere, we shall have in mind that the a0 is detectedusing its dominant 7rß decay mode.

The final aod system has isospin If=1 . For lf = 0(S-wave) it has spin-parity Jf = 1+ . The initial NNsystem can not be in the state Ii .= 1, JP = 1+because of the Pauli principle . Therefore near thethreshold the aodsystem is normally produced in theP-wave with quantum numbers Jf -- 0- , 1 - or 2- .The states with JP = 0- , 1- or 2- can be formed byan NN system with the spin Si = 1 and Ii = 1 and3. Neglecting the contribution of the higher partialwave li = 3 we can write the amplitude of reaction(a) in the following form

T(pp -+daö)=a+p .Sk .e* +ß+p . kS . e*

+-y+ S - k p - E* ,

(1)

where S = ONO'2 O'ON is the spin operator of theinitial NN system ; p and k are the initial and finalc.m . momenta; e is the deuteron polarization vector ;a+ , ß+ , y+ are three independent scalar amplitudeswhich can be considered constant near the threshold(at k -+ 0) .Due to mixing, the aö may also come from the fo .Then the aöd system will be in S-wave and the am-plitude of the reaction (b) will can be written as :

T(pn --> daö)==ao p-S k-E* +ßo p .k S .e*+yo S - k p - e* + eF S - e*,

(2)

where 6 is the mixing parameter and F is the foproduction amplitude . The scalar amplitudes a, ,P,y for reactions (a) and (b) are related as follows:a+ = ßa0, ß+ = ßß o , y+ = ßy0.

41

The differential cross sections of the reactions (a)and (b) have the following forms (up to the linear interms)

where

du (pp --> d aö) =

2p (Co + C2 cos2 oX3)

dSZ (pn --> d aö) =

(Co +C2 COS2 0p

_ _1

Cl cos 0Rba

2 + Co + C2 c0S2 0

+ Cl cos 0) ,(4)

Co =12 p2k2 [Ia0 12 + Iy 0 12 ] ,

Cl =p k [Re((eF)* (ao + 3ßo + yo ))]

,

C2 = 1p2

k2 [3 1ß0 12+2 Re(aoßo * + a0y 0 * + ß0y 0 *)] .

The differential cross section of the reaction pn -+dfo can be written as

in (pn .--}dfo ) =p IFI2 .

Near the threshold the differential cross sections (3)and (4) are proportinal to k 3 or Q3/ 2 , where Q is thec.m.energy release. At the same time u(pn -+ dfo) -k or V1Q.The mixing effect described by the term Cl cos0 inEq.(4) leads to the isospin violation in the ratio ofthe differential cross sections for reactions (b) and(a)

and to the forward-backward asymmetry in the re-action (b) :

ua(0 = 0°) - u' ,(0 = 180°) -

ClAa = u,(0 = 0°) + oa(0 = 180°)

Co + C2 .(7)

The latter effect was discussed in Ref.[8] where itwas argued that A,, can reach 8-15% at the energyrelease Q = (5 - 10) MeV. However if we take themixing parameter 11 2 = (8 f 3)% as it follows fromtheWA102 data than one whould expect much largereffect . Let us make simple estimations of the isospinviolation effects in the differential cross section ratioRab and the forward-backward asymmetry A,,, .The calculations of the differential cross section (3)within the framework of the two step model [9] re-vealed that Co - C2. We consider 3 possible solu-tions for the spin structure of the pn -+ da9 ampli-tude which satisfy this restriction:

ß o = 0, a0 = 'Y o , Co = C2 = p2k21,Y012,Cl = 2p kRe((eF)*-yo) ;

(8)

ao = 0~ ßo =

Co = G`2 =12 p2k2iß012,

Cl = 2p kRe((eF) *ßo) ;

1yo = 0, ao = -ßo , Co = C2 = 1 p2k21ß012,

Cl = 2p kRe((6F)*ßo) . (10)

Let us make numerical estimations of the effect atthe maximum COSY energy Tp =2.62 GeV whenp = 1.1 GeV/c and k = 0.25 GeV/c. According tothe two step model [9] the forward differential crosssection of the reaction (a) is equal to 140 nb/sr. Weassume that the forward differential cross section ofthe reaction pn -> dfo is the same . Then we have(Fj 2 -410 nb and neglecting possible phase factorsin the pn -~ d ao and pn -+ d fo amplitudes as wellas in the mixing parameter we find

Cl 2-A-Co+C2 =

1=0.35_0.54

(11).73

for solution i) and

Co+1C2N

I 1=0.5i0.8

(12)

for solutions ii) and iii) . Therefore the isospin viola-tion in the ratio of the forward differential cross sec-tions Rba, as well as in the forward-backward asym-metry A,, can reach 100% and more .

2 .

Reactions (c) and (d)

Near threshold the amplitudes of the reactions (c)and (d) can be written as

where SA =

ÄQ2 a'ON, Do, and Df are the scalar S-wave amplitudes descibing the ao and fo productionwhen the mixing is absent . The ratio of the differ-ential cross sections of the reactions (d) and (c) isgiven by

Rdc = (15)

The magnitude of Rde depends on the relative valueof the amplitudes Da and Df. If they are compara-ble (Da l - IDf I or 1Df12 » IDa12 the deviation ofRdc from 0.5 (which would correspond to the isospinconservation) might be 100% or more. Only in thecase IDf 1 2 « IDa12 the difference of IRdc 1 2 from 0.5will be small. However this possibility looks very un-likely. If we consider a two-step model of the reac-tions pd _+ 3He aö and pd -j 3He fo , involving thesubprocesses Pp-+ dir+ and 7r+n -3 p aolfo (see e.g .Ref.[10]), then we find

u(pd

'He aö) N a(7r+n -+ p aö)

(16)o'(pd

3He fo) - Q(lr+n -~ p fo) '

According to Ref.[9] u(7r+n -4 p ao) = Q(7r-p -4n ao) =0.5-1 mb at 2 GeV/c. A similar value ofo.(7r-p -} n fo) can be found using the resultsof Ref.[11] . Thus we expect that near thresholdv(pd -4 'He aö) ^v(pd -4 'He fo) . This would im-ply that the effect of isospin violation in the ratio Rdecan be quite large . As a possible estimate of the dif-ferential cross section we mention that the backwarddifferential cross section of the reaction pd -+ 3He 77'is about 0.1 nb/sr (see e.g . Ref.[10]) at Tp =2.4 GeV.Near threshold the forward differential cross sectionis expected to be the same.

3. Reaction (e)

Direct production of the ac in the reaction (e) is for-bidden . It can be only due to the fo - ao ixing:

a(dd -~ aö 'He) _a(dd -3 fo 4He) -

1612 . (17)

Therefore it would be very interesting to study thereaction

[3]

[4]

dd _~. 4He (?ro 71)

(18)

near the fo production threshold. Any signal of thereaction (18) will be related to the isospin breaking.It is expected to be much more pronounced near thefo threshold as compared with the region below thisthreshold.References :

N.N . Ach'sov et al ., Phys . Lett . B88 (1979) 367.[2] N.N . Achasov et al . , Phys . Rev. D56 (1997)

212 .

G. Janssen et al ., Phys. Rev. D52 (1995) 2690 .0. Krehl et al ., Phys . Lett . B390 (1997) 23 .B.O . Kerbikov et al ., nucl-th/0006017.

[6]

F. Close and A. Kirk, Phys . Lett . B489 (2000)

[7]

[8]

24 .

D. B'rberis et al ., hep-ex/0007019 .A. Kudry'vtsev et al ., JETP Lett . 72 (2000)410.

V.Yu. Grishina et al ., Eur. Phys . J. A9 (2000)277.

[10] L.A . KondratyukLett . 63 (2000) 1.

[11] E.L . Bratkovskaya et(1999) 165.

and Yu.N . Uzikov, JETP

al ., Eur. Phys . J . A4

'Institute for Nuclear Research, 60th October An-niversary Prospect 7A, 117312 Moscow, Russia6Institute of Theoretical and Experimental Physics,B. Cheremushkinskaya 25, 117259 Moscow, Russia* Supported by DFG and RFFI.

T(pd _+ 3 H aö) _

= /2-Da, SA " e, (13)

T(pd -+ 3He ao) _.--. (Da -!- ~Df) SA . s, (14)

The hypertriton nucleus is the simplest one amongthe hypernuclei and, hence, plays a special role intesting hyperon-nucleon interaction potentials . Themeasured value of binding energy is s - 0 .13 ± 0.05MeV [1] and the lifetime is given as (2 .46 -f- 0 .62-0.41) x 10-1° s [2]. Calculations show that in thislight hypernucleus the non-mesonic decay channels3HA -+ d+p and 3HA -+ p+n+n contribute onlyby about 1 .7% to the total decay rate f3H� [3] andpredict Ir3HA /rA = 1 .03 [4], where IPA is the freeA decay rate . Among the six mesonic decay chan-nels the strongest channels are 3HA -+ 3He-f-7r-and 3HA ---Yd+p+7r- . The decay branching ratioR = r( 3HA __+ 3He+7r- )/r( 3HA -+ all y modes)from experimental data has been estimated to be0.30 f 0 .07 [2] . The rates corresponding to the de-cay channels with 7r ° mesons are smaller by theisotopic factor 2. The cross section of the reactionpd -+ 3HAK+, estimated within the two-step modelof Ref. [5], is N 1 nb/sr near threshold. Experimen-tally the cross section of this reaction was measuredat SATURNE [6], but only an upper limit of the or-der nb/sr could be deduced.It would be interesting to measure the cross sec-tion of the reaction pd _+3 HAK+ at ANKE detect-ing the h+ meson and 311e nucleus from the decay3HA --}3 He -}- 7r- . Detection of the K+ meson and3He nucleus in coincidence reduces background . Theexpected angular dependence of the cross section isshown in Fig. 1 . The trajectories resulting from aGEANT simulation are presented in Fig. 2.Optimum conditions for the measurements are ex-

0_bv

ä 10

pd -'HAK'

. .. . ...

.. . . .... . . . . . . .

1 .2

0

Study of hypertriton production in the reaction pd -+ sHAK+

Yu. Uzikova,#, M . Büscher, V. Komarovb, F . Rathmann, H. Seyfarth, H . Ströher, S . Yaschenkob

2.0 -

:?. ;f

2.2

1ö6 i0

20

40

60

80

100

120

14Q ' 160 " 180U .m ., grad

Figure 1 : The c.m.s . cross section for the reactionpd -+ 3HAK+ at different energies (in GeV) of theincident proton estimated within the two-step modelof Ref. [5] .pected near threshold at Tp = 1.2 - 1.3 GeV. Thecalculated counting rate for detection of 'He andK+ from the reaction with formation of 3HA in theintermediate state is N N 3h`1 at a luminosityL = 1032 CM-2S-1 which can be obtained with a

high density unpolarized storage cell gas target or apellet target . The measurement of the cross sectionof the reaction will provide a test for the details ofthe 3HA-structure . The measurement of the angulardistribution of the 3He nucleus in the c.m.s . of the3HA nucleus over the full range 0 < Bc .n, . <_ 1800

would allow to determine the polarization of the hy-pertriton, analogous to the measurement of the po-larization of the A-hyperon in the decay A --+ per- .Such a polarization measurement may yield an addi-tional sensitive test for the reaction mechanism andthe hypertriton structure . It should be noted thatin the present first approach the contribution of the

Figure 2: Trajectories of K+-mesons (large deflectionangles) and 'He nuclei (small deflection angles) fromthe reaction pd _43 He7r-K+ for an energy of theincident proton of 1.2 GeV at ANKE.

channel pd L+ AdK+ -+3He 7r K+ has not been con-sidered yet.

a Kazakh State University, Almaty, Kazakhstan ;delegated to Joint Institute for Nuclear Research,Dubna, Russia .b Joint Institute for Nuclear Research, Dubna,Russia .#Supported by BMBF (WTZ grant KAZ 99/001) .

References:

[1]

M. Juric et al., Nucl . Phys . B 52, 1 (l973) .[2)

G. Keyes et al ., Nucl . Phys . B 67, 269 (1973) .[3] J . Golak et al., Phys . Rev . C 55, 2196 (1997) ;

Phys . Rev. C 56, 2892 (l997) .[4]

H. Kamada et al., Phys . Rev. C 57, 1595 (1998) .[5] V.I . Komarov, A.V . Lado, Yu.N. Uzikov,

J. Phys . G: Nucl . Part . Phys . 21, L69 (1995) .[6]

J. Kingler et al ., Nucl . Phys . A 634, 325 (1998) .

The reaction pp -> ppK+K- has been studied at theCOSY-11 installation at a beam momentum of p=3.356GeV/c [1, 2] . Since the four-momenta of the three pos-itively charged particles can be experimentally deter-mined, the K--meson can be identified via the missingmass method.

Studies on the Reaction pp --} ppK+K- close to Threshold at theCOSY-11 Facility

0 .1 0.2 4 0.30.4 0.5o.6missing mass (ppK+) [ GeV/c2 ]

Figure 1: Missing mass spectrum of the data (solid line)as well as that derived from Monte-Caxlo simulations onthe Eo (1385) (dashed line) .

In Fig. 1 the missing mass of the system ppK+ isshown . A significant signal at the mass of the K--meson can clearly be separated from the background .This background can be explained by the production ofthe heavy hyperons E°(1385) and A(1405) via pp -+pK+Eo(1385)/A(1405) -4 ppK+X. The distributionderived from simulations on the F,0 (1385) is also in-cluded in Fig. 1 and fits to the data within statistics .In total, 61 events are identified as pp -+ ppK+K- fi-nal state, with only a very small background contam-ination. These identified K+K- events may originatefrom the free as well as from the resonant productionvia the scalar resonances fo(980) and ao(980) .

The obtained distributions of the relative angles ofthe kaon-antikaon, proton-kaon, proton-antikaon andproton-proton systems are presented in Fig. 2, nor-malized to simulations, assuming a pure free K+K--production including the pp-FSI as well as effects fromthe Coulomb interaction [3] . Within the error bars,these distributions are consistent with an isotropic emis-sion of the particles and give no clear hint for neither acontribution of higher partial waves nor for further finalstate interactions .

C . Quentmeier* for the COSY-11 collaboration

0.5y0.45

0.40 .35

Ci 0.3'100 .25° 0 .20 .150 .10.05

1 -0 .5 0

0.50.45

a 0.4N.35C4 0.3b 0 .25° 0 .20 .150 .1

0 .05

References

0 .5 1

osay 0 .4

0=0.35

0 .3b 0.25

0.20.150.10 .05

-0 .5~ , 0~ 0 .5 ~1cos9*(K+ , K)

cos0*(p, K').-~ 0 .5

0 .45r

0 0 .5 1

a 0 .4~.0.35

0 .360.25I° 0.2-0.150.10.05

1 -0 .5 0 0.5 1

cosh*(p, K)

cos0*(pl, p2)

d)

Figure 2: Relative angles of the kaon-antikaon, proton-kaon, proton-antikaon and proton-proton subsystem .

Assuming a pure resonant production via thefo(980) -+ K+K- , the angular distribution in (a) is ex-pected to show a shape indicated by the solid line . Sincethe data do not show such a behaviour, we concludethat the free production dominates the K+K- produc-tion strongly andthat the production via the resonancesplays only a minor role .A preliminary absolute cross section at a beam mo-

mentum of p=3.356 GeV/c, corresponding to an excessenergy of Q=17 MeV with respect to the free K+K-production, is determinded to be [4]:

Q = 1 .80 nb ± 0.27 nb (stat.) f0.35 nb (syst.) .

[1] Annual Report 1999, IKP, ForschungszentrumJülich, JU1-3744, 41 (2000)

[2] Annual Report 1998/99, IKP, WestfälischeWilhelms-Universität Münster, 20 (2000)

[3] G. Fäldt and C . Wilkin, Phys . Nett . B 382, 209(1996)

[4] C . Quentmeier, doctoral thesis (in preparation) ,

Westfälische Wilhelms-Universität Münster (2001)

* Institut für Kernphysik, Universität Münster,48149 Münster, Germany

- real data40

"' Monte-Carlo simulation10(1385)35I

30

25

20

15

10~II~I

5

290

ö e0

70

60

so40

3020

10

0300

250

200

150

100

50

0

Energy dependence of the 11/E° cross section ratio.

P. Kowina and D. Grzonka for the COSY-11 collaboration

Recent measurements for the determaination of theratio ofthe total cross sections for the A and E0 produc-tion near threshold via the reactions pp -~ pK+A (E0)at COSY-11 [Sew99] showed .a strong discrepancy tohigh energy data [Fla84] . Close to threshold at excessenergies e < 13 MeV the A/E0 cross section ratio wasdetermined to be 28 ±s which exceeds the value at highexcess energies (e > 150 MeV) of about 2.5 by an orderof magnitude .

To explain this experimantal observation differenttheoretical investigations have started. In reference[Sew99] a strong E°-N final state interaction is favouredwhich is in accordance to other measurements .

Further, caculations within a meson exchange modeltaking into account pion and kaon exchange [Gas00] re-produce the measured ratio by a destructive interferenceof sr and K exchange amplitudes .

Within a factor of two also other models describethe data by including heavier exchange mesons and/ornucleon resonances [Sib00, Shy00] .

More data are needed for the development of suitablemodels for the hyperon production .

Therefore, cross sections were determined at addi-tional excess energies in order to determine the energydependence of the A/Eo cross section ratio.

El I,

.I . . . . I . . . . 11-1111111-1-11 1 .025 1 .05 1 .075 1 .1 1 .125 1 .15 1 .175 1 .2 1 .225 125

missing mass [ GeV ]

Figure 1: Missing mass distributions resulting fromevents with an identified proton and a Ii+ for beammomenta of 2.398 GeV/c and 2 .626 GeV/c correspond-ing to an excess energy of 20 MeVfor theA (upper part)and the E0 (lower part) production, respectively.

At different excitation enegies measurement of thereaction channels pp -+ pK+A and pp -+ pK+E0 wereperformed at the internal COSY-11 cluster target usingthe standard missing mass technique. The 4-momentumvectors of the final state proton and K+-meson were de-termined using the COSY-11 detection - and analysing

ca.Taan

References

20

0 PRL 83 (1999) 682 -'+ Dee 99, preliminary _0 July 00, preliminary

40

60

excess energy [MeV]

Figure 2: Cross section ratio of the A/Eo productionas a function of the excess energy. New data have beentaken during two beam times in December 1999 andJuly2000 partly at identical excess energies for increasing thestatistics and thus reducing the error bars in the finalanalysis .

system from which a missing mass distribution is ex-tracted. In Fig. '1 the missing mass spectra for thethreshold production of A and E0 hyperons are given,both at an excess energy of 20 MeV. The peaks of theproduced hyperons are clearly seen . Still - especiallyat the higher beam momentum - there is a rather largebackground due to wrongly identified K+ signals, whichwill be reduced in the final analysis after calibration ofthe newly installed Cerenkov detector [KowOO] .

Preliminary results of the analysis for the excitationfunction of the ratio for the production of these twohyperons at the same excess energy are given in Fig. 2.An excess energy range up to 60 MeV is covered by thedata which suggest a strong decrease of the ratio in theexcess energy range between 10 and 20 MeV.

[Sew99] S. Sewerin, G . Schepers et al ., Phys . Rev. Lett .83 (1999) 682.

[Fla84] V . Flaminio et al ., Compilation of Cross sec-tions, CERN HERA 84 01 (1984)

[Gas00] A. Gasparian et al ., Phys . Lett . B 480 (2000)273.

[Sib00] A. S1birtsev et al ., e-Print Archive nucl-th/0004022 (2000) .

[Shy00] R. Shyam, G. Penner, U. Mosel, e-Print Archivenucl-th/0010102 (2000) .

[KOW00] P. Kowina and M. Siemaszko, contribution tothis Annual Report .

High statistics measurement of the pp -+ ppq reaction at

Investigations of the q meson production via thepp -+ pprl reaction addresses the question of thestrength of the proton-77 interaction at low relativemomenta of the reaction particles . In the frame ofthe optic potential model this interaction can be ex-pressed in terms of phase shifts, which in turn aredescribed by the scattering length anIV and the ef-fective range of the potential . Usually the anN isdefined as a complex quantity, with the imaginarypart accounting for the r7N --+ 7rN process. The realpart of the scattering length is a direct measure forthe formation - or non-formation - of an q-nuclearquasi-bound state [1] . At present this very interest-ing issue whether the attractive interaction between7/-nucleon and nucleon-nucleon pairs is strong enoughto form a quasi-bound r7NN state remains open . En-couraging results indicate [2] that a three-body r7NNresonant state, which may be formed close to the ridthreshold, may evolve into a quasi-bound state forRe(a,7N) >_ 0.733 fm . Similarly, the close to thresh-old enhancement of the total cross section of thepp -4 pp~ [3] reaction was interpreted as being eithera Borromean (quasi-bound) - or a resonance qppstate [4], provided that Re(agN) > 0.7 fm . Contrary,recent calculations performed within a three-bodyformalism indicate [5] that a formation of a three-body ANN resonance state is rather not possible in-dependently of the qN scattering parameters . More-over, the authors ofreference [6] exclude also the pos-sibility of the existence of an r1NN quasi-bound state.However, results of both calculations [5, 6], althoughperformed within a three-body formalism, used theassumption of a separability of the two-body ?IN andNN interactions, and hence the new quality in thethree-body r7NN-interaction is not excluded and de-serves experimental investigations .The COSY-11 collaboration performed a high statis-tics measurement of the pp --+ pprl reaction at anexcess energy of Q = 16 MeV. The determination ofthe four-momentum vectors for both outgoing pro-tons of each registered event gives the complete in-formation of the 7Ipp-system allowing for the investi-gations of the Op and rlpp interactions . The analysisof the Dalitz-plot aims for the extraction of the stillnot well established value of the fl-proton scatteringlength . The analysis of the data is still in progress .At present the data were corrected for the meanbeam momentum changes (see Fig. 1) during the 10days of data taking . The missing mass distribution,shown in Figure 2, will further be corrected for ef-fects of the time dependent relative shifts betweenthe beam and the target using the method describedin reference [7]. After this is done the Dalitz- and t-plot analysis will be performed. The t-plot will showan enhancement at the four-momentumsquare whichcorresponds to the mass of the particle exchanged be-tween the interacting protons during the pp -4 pp71reaction .

P. Moskal* for the COSY-11 collaborationFor the calculation of the differential acceptanceof the detector system - needed to correct for theDalitz- and t-plots - we will take advantage of the re-sults of the angular distributions of the ejectile planemeasured by the TOF collaboration [8] .

Figure 1: The dashed curve denotes the difference of themeasured proton beam momentum distribution from itsnominal value of 2.027 GeV averaged over the 10 daysof the COSY running. The solid line shows the beammomentum distribution after the correction for the meanvalue of the beam momentum, determined in each 10second intervals, was applied.

4000

wU

ö

References :

Cracow, Poland

COSY-11

Figure 2 : Missing mass distribution for the pp -+ ppXreaction determined by means of the COSY-11 detectionsystem at a beam momentum of 2.027 GeV. A shadedarea depicts the missing mass spectrum originating fromthe multi pion production . In order to guide the eyebelow the signal from the q meson production, the multipion distribution is approximated by a straight line .

[1] A. Svarc, S. Ceci, nucl-th/0009024[2] N. V. Shevchenko et al ., nucl-th/9908035[3] H. Calen et al ., Phys . Lett . B 366 (1996) 39 ;[4] S . Wycech, Acta Phys . Pol. B 27 (1996) 2981[5] A. Fix, H. Arenh6vel, nucl-th/0006074[6) H. Garcilazo, M. T. Peiia, nucl-th/0010081[7] P. Moskal et al ., nucl-ex/0010010[8] E. Roderburg et al ., Acta Phys. Pol. B 31

(2000) 2299* Institute of Physics, Jagellonian University, 30-059

Data on the rl' meson production in the reactionchannel pp --} pp X, one ofthe main research topics [1-3]of the internal beam facility COSY-11 at COSY-Jülich,have been taken at excess energies of Q = 26.5, 32.5and 46.6 MeV [4]. The event selection was performed byaccepting events with two identified protons. The four-momentum determination of positively charged ejectilesyields a full event reconstruction for the reaction typepp -+ ppX and the X-particle system can be identifiedusing the missing mass method. Therefore, kinematicaldistributions of the reaction ejectiles can be studied.

In Fig.1 the resulting angular distributions areshown. The quoted error bars include statistical andsystematical errors . Within the errors the presenteddistributions at excess energies of Q = 32.5 MeVand Q = 46 .6 MeV are compatible with an isotropicemission . This is consistent with the result from theDISTO collaboration at an excess energy of Q = 144MeV [6] .

2E:i 1.8 Q=315MeVOi 1.6

b 1,v 0.80.60 .40 .2

Near Threshold Production of q' Mesons in the Proton-ProtonScattering

-1

-0.5 .0

0.5

1cos9*(T ' )

A. Khoukaz* and C . Quentmeier* for the COSY-11 collaboration

Figure 1: Angular distributions of the emitted ??'mesonsin the center of mass system for the reaction pp -+ ppil'at Q = 32.5 MeV and Q = 46.6 MeV.

In Fig.2 the extracted total cross sections (filled cir-cles) are compared with other existing data [1, 2, 5, 6] .The solid line indicates a fit to the data resulting frompure s-wave three body phase space calculations mod-ified by the proton-proton final state interaction (FSI)and Coulomb effects [7] which describes the whole setof existent data even up to excess energies of Q = 144MeV. In addition, the dashed line shows a correspond-ing calculation but neglects both final state interactionsand Coulomb effects. This curve was arbitrarily fixed tothe present data point at Q = 26.5 MeV. From the com-parison of these two curves with the data we concludethat the excitation function can be described withoutfurther contributions from higher partial waves and inparticular without strong effects of an 77'-proton inter-action . The formerly discussed possibility of a repulsive77'-proton interaction [8,9] seem to be of minor impor-tance. This observation is in agreement with the re-sult [3] that the 7'-proton scattering length is small andsimilar to the one for the 7r°-proton system .

a'210C0wVVy

0V10

10

- 3't DISTOSPES-III

O COSY-11"

presentwork, preliminary

References

Figure 2: Total cross sections for the reaction pp -4

pprl' as function of the excess energy Q. Filled circlescorrespond to the data presented in this paper andopencircles, triangles and stars correspond to data from [1,2,5,6], respectively. The curves are explained in the text .

* Institut für Kernphysik, Westfälische Wilhelms-Universität, Münster, Germany

[1] P. Moskal et al., Phys . Rev. Lett . 80 (1998) 3202 .

[2] P. Moskal et al ., Phys . Lett . B 474 (2000) 416.

[3] P. Moskal et al., Phys . Lett . B 482 (2000) 356.

[4] C. Quentmeier, doctoral thesis, WestfälischeWilhelms-Universität, Münster, Germany, inpreparation (2001) .

[5] F. Hibou et al ., Phys . Lett . B 438 (1998) 41 .

[6] F. Balestra et al ., Phys . Lett . B 491 (2000) 29 .

[7] G. Fdldt and C. Wilkin, Z. Phys . A 357 (1997)241.

[8] V. Baru et al ., Eur. Phys . J . A 6 (1999) 445.

[9] P. Moskal et al., Acta Phys . Pol. B 29 (1998) 3091 .

Phenomenological analysis of near-threshold production of gyr o , rl, and 71' mesons in proton-protoncollisions .

A comparative study of the production of mesons withsignificantly different masses encounters the difficulty offinding a proper variable at which the observed crosssections can be compared. In case of pp -+ ppX re-actions a total cross section is an integral over phasespace, weighted by the square of the transition matrixelement and normalized to the incoming flux factor [1] .Therefore we propose the volume of the available phasespace for the produced particles [2] as a variable suitedto compare the cross sections . Figure 1 shows the yieldof gyro, 77, and 77' meson production in the proton-protoninteraction as a function of the available space phasevolume . The yield is defined as the cross section mul-tiplied by the corresponding flux factor, and divided bythe ISI reduction factor accounting for the repulsive in-teractions of protons in the initial state [3]. Hence, thechosen dimensionless quantity ISI , depends on the pri-mary production amplitude Mo and on the final stateinteraction among the produced particles only . Thus,the observed differences in the production yield for thedifferent mesons, as shown in Figure 1, indicate directlythe difference in the primary production dynamics con-voluted with the interactions in the exit channel. Thedata [4] for Tro, 77, and rl' meson production are groupedon parallel lines indicating a dependence according tothe power low: ISI - a * Vp°hs l . A similar behaviourwas also found when plotting the data versus the max-imum center-of-mass momentum of the produced me-son normalized to its mass [5] . The dynamics of thepp -+ ppX reaction would be independent of the pro-duced meson, all the data points in Figure 1 would layon the same line .

Vphs [ McV2

P. Moskal* for the COSY-11 collaboration

Figure 1 : Yield defined in text for the reactions pp -+Pp?7 (squares), pp -+ pp7r o (diamonds), and pp -+ ppt7l (cir-cles,triangle) [4], Thefilled squares and circles indicate recentCOSY - 11 results .

Assuming that the production amplitude factorizes intoan energy independent primary production amplitudejMoI and the FSI and ISI factors we derived from theexperimental data the IMo I values for each discussed me-son [2] . Further we normalized the obtained IMO'7 1 and

IMö'I to the JMöo 1 . These ratios, presented in Figure 2,are independent of the prescription used for the proton-proton interaction . The increasing strenth of the ratioIMö 111Mö 0 1 at low Vph s (Figure 2b) indicates a muchstronger 71-proton FSI than the 7ro-proton one. Note,however, that the ratio for the 77' meson is constant overthe phase space range considered (Figure 2b) . This al-lows us to conclude that the 77'-proton interaction is inthe order of or weaker than the 7ro-proton one.

oF-51.5

FO

2.5

0 .5

0

0.5

W-V t

0 , .

.,

. .10-~

, . . . . . 1 . . . . . .10 . . . . .102

103Vphs [ McV2

a)

b)

Figure

2:

The

ratios

of

a)

1Möj/jMo 0 jb) 1Mö"j1jMö0 I extracted from the data,FSI enhancement factor of reference [6]References :

andassuming the pp-

[1] E. Byckling, K . Kajantie, "Particle Kinematics",John Wiley & Sons Ltd. (l973) .

[2] P. Moskal et al ., Phys . Lett . B 482 (2000) 356.[3] C . Hanhart, K . Nakayama, Phys . Lett . B 454

(1999) 176.[4] F. Balestra et al ., Phys . Lett . B 491 (2000) 29 ;J. Smyrski et al ., Phys . Lett . B 474 (2000) 182;P. Moskal et al ., Phys . Lett . B 474 (2000) 416;F. Hibou et al ., Phys . Lett . B 438 (1998) 41 ;P. Moskal et al ., Phys . Rev. Lett . 80 (1998) 3202 ;H . Calen et al ., Phys . Rev. Lett . 79 (1997) 2642 ;H. Calen et al ., Phys . Lett . B 366 (1996) 39 ;E. Chiavassa et al ., Phys . Lett . B 322 (1994) 270;A.M . Bergdolt et al ., Phys . Rev. D48 (1993) R2969;H.O . Meyer et al ., Nucl . Phys . A 539 (1992) 633;A. Bondar et al ., Phys . Lett . B 356 (1995) 8;[5] H . Machner, J. Haidenbauer, J. Phys . G 25 (1999)

R231 .[6] B.L . Druzhinin et al ., Z. Phys . A 359 (1997) 205

* Institute of Physics, Jagellonian University, 30-059Cracow, Poland

Near Threshold Production of w Mesons in the pp -+ ppw Reaction

A. Khoukaz* and C. Quentmeier*

Studies on the w meson production in the proton-proton scattering provide valuable information on theproperties of this vector meson and relevant produc-tion processes in the elementary nucleon-nucleon inter-action . Recent calculations on the pp -+ ppw reaction [l]demonstrate a significant influence of different produc-tion mechanisms on the angular disribution of the emit-ted w mesons . Data for the reaction channel pp -> ppXtaken at COSY-11 at beam momenta of 3.292 GeV/c,3.311 GeV/c and 3.356 GeV/c have been analyzed inview of the w meson production [2] . The excess ener-gies coverd by this data are Q = 202.3 MeV, 208.3 MeVand 222.5 MeV. The event selection was performed byaccepting events with two identified protons. The four-momentum determination of positively charged ejectilesyields a full event reconstruction for the reaction typepp -> ppX, and the X-particle system can be identifiedusing the missing mass method. Therefore, kinematicaldistributions of all reaction ejectiles can be studied indetail .

In Fig.1 the resulting angular distributions for threedifferent beam momenta are shown. The quoted er-ror bars include statistical and systematical errors ex-cept contributions from overall systematical uncertain-ties (e.g. luminosity determination) . Obviously, the ob-served distributions, which for symmetry reasons haveto be symmetric about cos9*(w) = 0, indicate the pres-ence of higher partial waves than pure s-wave .

L 2000

ä 1600

0: 1200b

800

400

0

1600

1200

800

400

0

1600

1200

800

400

-1 -0 .8 -0.6 -0.4 -0.2 0

0.2 OA 0.6 0.8 1Cos 0*(0) )

Figure 1: Angular distribution of the emitted w mesonsin the center of mass system for the reaction pp -+ ppwat Q = 202.3 MeV, Q = 208.3 MeV and Q = 222.5 MeV.

for the COSY-11 collaboration

Figure 2: Total cross sections of the reaction pp -4 ppwas function of the excess energy Q. The curves are ex-plained in the text .

In Fig.2 the resulting total cross sections (filledsquares) are compared with other existing data [1, 3,4] .The solid line indicates a parametrisation of the excitation function of the pp -+ ppw reaction on basis ofa one-pion exchange model [5]. While the high energydata can fairly be described by this calculations, distinctdeviations at lower excess energies (Q < 400 MeV) arevisible, which might partly be caused by the neglectedfinal state interactions . The dashed line of Fig.2 repre-sents results of investigations on the w meson productionwithin ameson-exchange model taking into account con-tributions of the 7r, p and w exchange as well as the NNfinal state interaction [1]. These calculations are validfor excess energies below Q - 100 MeV and describe thelow energy data fairly well. However, a complete calcu-lation describing the available data in the whole rangeof displayed excess energies is still missing.

* Institut für Kernphysik, Westfhlische Wilhelms-Universitdt, Minster, Germany

References[1] K. Nakayama et al ., Phys . Rev. C 57 (1998) 1580.

[2] C. Quentmeier, doctoral thesis, WestfälischeWilhelms-Universität, Münster, Germany, inpreparation (2001) .

[3] F. Hibou etal ., Phys . Rev. Lett . 83 (1999 492.

[4] F. Balestra et al ., nucl-ex/0011009 (2000) .

[5] A. A. Sibirtsev, Nucl. Phys . A 604 (1996) 455.

r-, 0.160.140.120.1

,~ 0.080.060.040.02

°-1 -0.5 0

Results on y-Production in the Reaction pd _+ 3He qH-H. Adamt, I. Geckt, A. Khoukazt and T. Listert

for the COSY-11 collaboration

The study of near-threshold 77-meson production inproton-deuteron scattering is motivated by the discus-sion of the underlying production processes . The exist-ing data are described by two competing models . In thetwo-step model [1, 2] in the first step the proton and onedeuteron nucleon interact and a pion is emitted, whichitself interacts in a second step with the remaining nu-cleon to create the 71 . Different to this, the resonancemodel describes the 7l-production via the excitation ofthe S11 resonance N* (1535) [3] . Existing data, coveringthe nearest threshold region up to excess energies of 7MeV [4] and one data point at 50 MeV [3] cannot bedescribed as a whole by one of these models . In orderto clarify the situation, measurements were carried outat COSY-11 at four different excess energies between 5and 20 MeV.

0.14ü0.12

0.1n 0.08b 0.06

0.040.02

°-1 -0 .5 0

0.09A 0.08`~ 0.070 0.06b 0.05'0 0.04

0.030.020.01

cos O*

cose*

cos O*

cosO*Figure 1: Differential cross sections for the reactionpd -} 3He rl, referring to the scattering angle of theproduced 3He nuclei . The data are taken from [5] and[6] .

At COSY-11 the four-momenta of positively chargedparticles can be completely reconstructed. For the iden-tification of undetected particles or systems of particlesthe missing mass method is used .For the determination of differential cross sectionsmissing mass spectra have been produced for differentbins of the center of mass scattering angle 0* of the3He nuclei . In each of these spectra the missing masspeak has to be separated from the background and thecontent of the 77 peak has to be corrected for acceptance .Figure 1 shows differential cross sections of the re-action pd -_+3 He 77 at four excess energies . As can beseen, even at excess energies of up to 20 MeV the dataare in accordance with the assumption of an isotropicscattering .For the determination of total cross sections the data

10

10

10zexcess energy [ MeV

Figure 2 : Excitation function of the reactionpd -+ 'He q near threshold .

have to be normalized for the luminosities . The mon-itoring of the luminosity is done by simultaneous mea-surement of the elastic scattering process pd -> pd . Theabsolute normalization can be achieved by comparingthe measured differential data to literature data . Asthis is not yet done, the COSY-11 data point at an ex-cess energy of 5 MeV was fixed to the one measured inSaclay at the same beam momentum ; as the relationsof the luminosities at the other energies are known, theexcitation function in the intermediate excess energy re-gion can be filled with the COSY-11 cross sections . Theresult is shown in Figure 2 . It has to be pointed outthat the data have been taken within approximately 2.5days ofmeasurement each and that the statistics showncorrespond to roughly 2/3 of the complete data sample .

The COSY-11 data suggest that there is a tran-sition between the two-step process and the resonantproduction . Nevertheless, for a better understanding ofthe shape of the excitation function, more data in thenear threshold region are needed .

t Institut für Kernphysik, Westfälische Wilhelms-Universität Münster

References(1]

K. Kilian, H. Nann, AIP Conf. Proc . No.221(1990),185

[2]

G. Fäldt, C. Wilkin, Nucl . Phys . A 587 (1995), 769[3]

M. Betigeri et al ., Phys . Lett . B 474 (2000), 267[4]

B. Mayer et al ., Phys . Rev. C 53 (1916), 2068[5]

H.H. Adam, diploma thesis,

WWU Münster(2000)

[6] I. Geck, Staatsexamensarbeit, WWU Münster(2000)

A threshold Cerenkov counter for the

P. Kowina* andM. Siemaszkot

Recently the COSY-11 collaboration [Bra96] hasmeasured the production of A andE0 hyperons at equiv-alent excess energies up to 13 MeV [Sew99] . Now theprogram of studying the associated strangeness produc-tion in pp -+ pK+A(E°) reactions is extended to higherexcess energies, up to 60 MeV [Pro99].

In reactions of this type one of the main difficul-ties is to identify short-lived K+ by the time of flightmethod. Positively charged kaons do not,reach the S3detector and merely only 30% pass through S1 (Fig . 1) .Therefore one has to use the time of flight measure-ment between the target and S1 . The start time for thekaons is calculated by tracking back the proton, regis-tered in S1 and S3, through the known dipole magneticfield to the target position . The stop signal is providedby the scintillator arrangement S1 . This procedure al-lows to determine the four momentum vectors of theproton and K+, while the unobserved neutral hyperonhas to be identified by the misssing mass method.

*FZ-Jülichtlnstitute of Physics, University of Silesia, Poland

Figure 1 : Schematic view of the COSY-11 detectionsetup showing the position of the Cerenkov counter.

For a clean event selection a reduction of backgroundorginating from the misidentification of a pion as a kaonis crucial. Pions and kaons with the same momentumcan be distinguished by their velocity . For example incase of the reaction pp --+ pli+E0 at a proton beammomentum of 2.576 GeV/c one has < ß,r+ > = 0.975and < (3K+ > = 0 .720 . For a better identification ofthe kaons a threshold Cerenkov counter has been in-stalled at the COSY-11 experimental setup. As an ac-tive medium pure water was chosen . The container ofthe Cerenkov counter has been built in the Institute ofPhysics, University of Silesia in Katowice (Poland) . It

51

for the COSY-11 collaboration

cÜ

180018001400120010008008004002000

18001800140012001000800800400200

COSY-11 facility

invariant mass spared of the second particle [ GeV2/c4 ]

Figure 2 : Spectra of the invariant mass squared of thesecond particle for the events without a) and with theuse of a veto signal by the Cerenkov counter b) .

has a rectangular shape with dimensions 85x85x5 cm3 .As inner reflecting layers 2.5 mm thick chrome-platedsteel plates (type H17) have been used . In the upperpart eight photomultipliers readout the volume . Thedetector can be inclined with respect to the direction ofincoming particles (see Fig. 1), which allows to optimizethe conditions of reflection of the Cerenkov light insidethe radiator . Additionally in front of the radiator a leaddegrader is installed, since the maximum,Q value of theoutgoing K+ can exceed the threshold ß value for wa-ter. The degrader thickness can be adjusted accordingto the given beam momentum .

The new Cerenkov detector has been used for thefirst time during measurements of the reactions pp -4pli+A and pp -+ pK+E° in July 2000 . Figure 2 showspreliminary spectra of the invariant mass squared ob-tained from the particle identification procedure with-out a) and with b) including the information from theCerenkov counter. Using the Cerenkov detector as aveto results in a reduction of the pion background by afactor of three without loosing kaon yield .

References[Sew99] S. Sewerin et al ., Phys . Rev. Lett . 83 (1999)

682.

[Pro99] COSY Proposal No. 87 (1999) and No. 87.1(2000) .

[Bra96] S. Brauksiepe et al ., Nucl . Instr. & Meth . A 376(1996) 397.

References:

Monitoring of the beam geometry during the measurement

In the previous year we developed amethod for monitor-ing the geometrical dimensions of a synchrotron beamat the target position for internal target installations [1] .The technique is based on the analysis of the momen-tum distribution for elastically scattered protons and itscomparison with the distributions simulated with differ-ent beam and target conditions . The information of thechanges of the size and position of the beam relative tothe target during the measurement allows to improvethe precision of the momentum reconstruction of thecharged particles, which consequently leads to a betterresolution of the identification of an registered events .The applicability of the technique is demonstrated herefor controlling the size and position of the proton beamrelative to the target when stochastic cooling was usedat the synchrotron COSY for the first time in Febru-ary 1998 . The horizontal stochastic cooling [2] is usedto squeeze the proton beam in the horizontal directionuntil it reaches an equilibrium between the cooling andthe heating due to the target . The size of an uncooledbeam increases during the cycle, as can be seen in Fig-ure la, which shows the spreading of the beam in thevertical plane during the 60 minutes cycle . This was ex-pected since stochastic cooling in the vertical plane wasnot used in this case . The influence of the applied cool-ing in the horizontal plane is clearly visible in Figure 1b .During the first five minutes of the cycle the horizontalsize of the beam of about 2 - 1010 protons was reducedby a factor of two, reaching the equilibrium conditions,and remaining constant for the rest of the COSY cycle .The movement of the beam relative to the target dur-ing the cycle is quantified in Figure 1c . The shift ofthe beam denotes also changes of the average beam mo-mentum, due to the nonzero dispersion at the targetposition . The beam reaches stability after <15 minutes.This can be understood as the equilibration betweenthe energy losses when crossing 1 .6 - 10 6 times per sec-ond through the HZ cluster target and the power of thelongitudinal stochastic cooling which does not only di-minish the spread of the beam momentum but also shiftsit as a whole.

* Institute of Physics, Jagellonian University, 30-059Cracow, Poland

[1] P. Moskal et al ., Nucl . Instr . & Meth . A in print,e-Print Archive: nucl-ex/0010010

[2] D. Prasuhn et al ., Nucl . Instr . & Meth. A 441 (2000)167

P. Moskal* for the COSY-11 collaboration

0.6

0.6

Ü12 0 .4

10000

ä0

E 5000

-1

cycle at COSY-11

- -0-. - .--»--e-

+-~-f.-0-

00 20 40 60time in cycle [ min)

d)

Figure 1: The vertical a) and horizontal b) beamwidth (one standard deviation) determined for each fiveminutes bins of the COSY cycle.c) Relative settings of the COSY proton beam and thetarget centre versus the time of the measurement cycle.d) Changes of the luminosity during the cycle . A steepdecrease on the beginning is caused by the movementof the beam out from the target centre .

n0 .2

00 20 40 60

time in cycle [ min ] a)

0.6

0.4U

0 .2

°0 20 40 60 b)time in cycle [ min ]

0

E-0.2

ax

-0.4

0 20 40 60 c )time in cycle [ min ]

Differential Cross Sections Measurement for the p +p -+ d + ?r+ Reaction at 850 MeV/cThe GEM Collaboration

The reaction p + p -+ d + 7'+ was recently studiedclose to threshold [1,2] and the time reversed reactionat somewhat higher energies [3] . In this energy domainonly three partial waves contribute to the cross section :

The total cross section can be parameterised in terms ofthe pion P-state and S-state . Since the amplitude for thetransition 1 is much smaller than the one for the transition3, the first one can not be extracted from the total crosssection . However, angular distributions of the differen-tial cross sections are sensitive to this weak partial wavethrough an interference term . In an Legendre polynomialexpansion

4-7rdd (o)= Ao+A2P2[cos(B)]

ffiis the interference term contained in A2, while Ao is thetotal cross section . Analysis of the near threshold angu-lar distributions yielded a sizeable interference term [1] .This is supported by predictions of a phase shift analysis(PSA), where these data are not included [4] .

Fig. l : Angular distribution of the differential cross sections ata beam momentum of 850 MeV/c. The full curve shows theLegendre polynomial fit Eq. 4 while the dotted curve is thePSA prediction.

On the contrary the data from Ref.

[3] favour more aninterference of negligible size. In order to study this am-biguity we have measured the reactionp+p --} d+?'+ at

an energy between the two diverging data sets. In this ex-periment recoiling deuterons were measured employingthe germanium wall

References

[5] .

SAID SP96RitcltieGEM98HeimbergPasyukfit E (no interference)presentAebischerPreedomAxen

(4] C. H. Oh et al., Phys. Rev. C 56, 635 (1997) .

Fig.2: Ratio between the Legendre coefficients as function ofthe dimensionless pion centre of mass momentumr1=Am/pi.

The high statistics data were complemented by a zerodegree measurement employing the magnetic spectro-graph BIG KARL [1] . A Legendre polynomial Eq. 4was fitted to the data. A term proportional to the 4thorder Legendre polynomial was found negligible. Theresulting ratio of the Legendre coefficients is shown inFig. 1 together with all data previously measured in thisenergy range. Also shown is is PSA prediction and thecurve obtained under the assumption of a negligible s-wave amplitude. The present point is in agreement withthe near threshold data and supports the data from Ref.[6], while it disfavours the data from Ref. [3] .

[1] M. Drochner et a1.,Phys . Rev . Lett. 77, 454 (l996) ;Nucl . Phys. A643,55 (1998) .

[2] P Heimberg et al., Phys . Rev. Lett . 77,1012 (1996) .

[3] E . A . Pasyuk et al., Phys . Rev. C 55,1026 (1997) .

[5] M. Betigeri et al ., NuclearInstr. Methods in PhysicsResearch A 421, 447 (1999) .

(6] B. G. Ritchie et al ., Phys . Rev. C 24,552 (1981) .

2p('So) --> d(3S1) +7r+ in P-state (1)2p(3P,,) -~ d(3S1) + z.+ in S-state (2)

2p(1SD1) --} d(3S1) + 7r+ in P-state. (3)

2600i

2400J

2200!

2000-

1800-

1600

1400

1200

10W

Kinematical Aspects Of Meson Production in p+d ReactionsThe GEM Collaboration

The deuteron is a loosely bound system with a largedistance between the two nucleons . It seems therefore agood testing ground for the impulse approximation . Inaddition, its wave function as well as those of the pro-duced light nuclei are believed to be well known and onecan hope that a theoretical treatment in the three nucleonsector might be possible .

Meson production mechanism in the p + d -4 3He +meson reaction can have several contributions . Therecan be a direct production, i .e . radiation of a meson offa nucleon . However, nuclear resonances can be involvedas intermediate state. These are different N*- and A-resonances, depending on the quantum numbers of themeson. Fig . 1 .

PP(Mev/c)

Fig . 1 : Excitation ofbaryon resonances as function oftheproton beam momentum for the indicated meson . Also shownare the thresholds for neutral meson production . Some selectedresonances and mesons are indicated.

shows the dependenceofmass of the baryon resonance asfunction of the beam momentum. The range correspondsapproximately of the momentum range of the COSY ac-celerator in Jülich . Also shown are some selected res-onances . The right hand y-axis shows the mass of theproduced neutral meson, or the total mass of the electri-cal neutral multi-meson system . Also indicated are thethresholds for neutral meson production. Here we haveconcentrated on narrow states . Also the threshold for twocharged pion production is shown.

Almost all resonances above the two pion thresholdsdecay into a nucleon plus two pions, sometimes with apion and a A as intermediate states . Two resonances aredifferent : The P33 A(1232) can decay only into pion andnucleon and the S1 1 N*(1535) couples strongly to the71-nucleon channel . GEM, therefore, has studied the re-action mechanism in the range of these two resonances[1,2] .

References

3000 .0 0 .2 0.4 0.6 0.8 1 .0 1 .2 1 .4 1 .6 1 .8 2.0 2 .2

11=P /m

Fig . 2 : The momentum transfer q as function of the mesonrelative centre of mass momentum 77 . The upper curve is for77-production the lower for w production.

In the reactions of interest one is dealing with largemomentum transfers . This is shown in Fig . 2 for the re-actions with the neutral mesons. While the momentumtransfer for thep -{- d -+ 3He -}- rl decreases strongly withincreasing beam momentum is the dependence of q in thecase of p + d -_~ 3He + 7r ° reaction rather weak . Fromthe numbers involved one can estimate that pion produc-tion can occur on one target nucleon, whereas the largemomentum transfer in the case of rl- production makessuch a mechanism unlikely. Both target nucleons have toparticipate making two step processes very likely. Onecan, therefore, expect rather dramatic differences in thereaction mechanisms and observables in these two reac-tions . While the first reaction is dominated by one pionexchange the later one will have more andprobably com-plicated graphs contributing to the cross section.

[11 M. Betigeri et al., Phys . Lett . B472 (2000) 267 .

[21 M. Betigeri et al., Nucl . Phys. A (in press) .

The study of meson production on the deuteron is thefirst step towards an understanding of meson productionon nuclei and the related in-medium effects . In a firstapproximation, the reaction can be assumed to be mainlya nucleon-nucleon reaction with the second nucleon inthe deuteron being a mere spectator [1] . However, thestruck nucleon has a Fermi motion and thus an effec-tive mass. In addition rescattering on the spectator nu-cleon may take place. All these processes do not takeplace reactions on the nucleon . The theoretical attemptsin p + d -4 (A = 3) + 7r have not been particular suc-cessful although a lot ofeffort was devoted to this subjectover the years [2] .

Charged and Neutral Pion Production in p+d Reactions in the A-Resonance RegionThe GEM Collaboration

1000 " Boo

A 750

06%"

a rt

Fig. 1 : Angular distributions for the recoiling 3He ions fromthe reactionp -;- d _4 3He + 7r° . The beam momenta (inMeV/c) are indicated next to the appropriate curve.

However, also uncertainties in the data body may be re-sponsible for this situation. GEM has, therefore, startedto measure the two reactions over a large range of beammomenta . While the data taken at momenta of 750MeV/c, 800 MeV/c and 850 MeV/c are published bynow [3], we will present here the new data taken at 950MeV/c, 1000 MeV/c, and 1050 MeV/c COSY beam mo-menta . In Fig . 1 the angular distributions for the recoiling3He are shown .

For the 7r-production very close to threshold isotropicangular distributions are observed . For higher beam mo-menta the angular distribution becomes backward peakedfor the heavy recoil . For a beam of 750 MeV/c it hasan almost exponential slope. For higher momenta anisotropic component shows up with increasing impor-tance with increasing beam momentum . One point mea-

sured at cos(9) = -1 which corresponds to zero degreein the laboratory was measured with the magnetic spec-trograph BIG KARL, the other data were obtained withthe GE-wall [4] .

The data were compared against different publishedcalculations. An example is given in Fig . 2 for thep + d -* 3 He +0 reaction measured at a beam momen-tum of 1050 MeV/c which corresponds to a beam energyof 470 MeV/c . This energy is well above the maximumof the A-resonance .

Fig. 2 : Angular distribution ofthe recoiling 3He from thep + d -> 3He + 7r° reaction at 1050 MeV/c . The modelcalculations are from sources indicated in the figure .

References

[1] M Ruderman, Phys . Rev. 87 (1952) 383 .

Shown are calculations performed by Ueda [5], Greenand Sainio [6], and by us in a modified Locher and We-ber model [7] . The first model overestimates the data bya factor of hundred, although it is claimed to be a uni-tary approach . The second calculation was claimed towork only in the backward region . This is supported bythe present data. For the calculations within the Locher-Weber model an Eckart form of the 3He wave functionwas assumed with parameters fixed to the charge distri-bution obtained from electron scattering. For this calcu-lation a normalisation factor of 1 .5 was found necessary .

[2] L . Canton, G. Cattapan, G . Pisent, W Schadow, J .P Svenne, Phys . Rev. C 57 (1998) 1588 ; L . Cantonand W Schadow, Phys. Rev : C 56 (1997) 1231

(3] M. Betigeri et al., Nucl . Phys . A (in press) .

[4] M. Betigeri et al., Nucl . Instrum . Methods Phys .Res. A421,447 (1999) .

[5] T. Ueda, Nucl . Phys . A505, 610 (1974) .

[6] A . M. Green and M. E . Sainio, Nucl. Phys . A 329(1979)477 .

Experiments searching for the charge and isospinsymmetry breaking effects were proposed and presentedat COSYPAC. The detailed motivation for such a studywas given in COSY Proposal No . 59 . The basic ideaof this investigation is the charge and isospin symmetrybreaking dueto 7r° -77 meson mixing . A model forchargeand isospin symmetry breaking was developed and thecalculations of the expected symmetry breaking effectswere performed . The model description and the resultsof the calculations were published in Ref . [1] .

In the first step of this investigation, the energy depen-dence of the cross sections ratio for thep+d -~ aH+7r+and p + d -> 3He + 7r° reactions should be measured.The model predict variations of the cross sections ratioby about 20% at a beam energy corresponding to the qproduction threshold. Such a strong effect is predictedfor a mixing angle of 0.015 . This value is suggestedby many QCD based calculations . As follows from themodel calculations the largest symmetry breaking effectis expected at large relative angles between the incidentproton and the outgoing pion . The crucial point for dis-covering an isospin symmetry breaking effect is the mea-surement of beam energy dependence of the cross sec-tions ratio enabling finally to extract the meson mixingangle . The variation of the cross section ratio with thebeam energy as predicted by the model [1] is shown inFig . 1 .

2.4

2.2

2

Investigations of Charge and Isospin Symmetry Breaking at COSYThe GEM Collaboration

880 890 900 910beam energy [MeV]

Fig . 1 : Ratio of cross sections for the p + d --> 3H + 7r+ andthe p + d -> 3He7r° reaction for the indicated angle as afunction of the beam energy [1] .

'

The experimental method of determining the energy de-

56

[7] M. P Locher and H. J. Weber, Nucl . Phys . B76,400(1974) .

pendence of the ratio of cross sections is based on si-multaneous detection of 3H and 3He using the magneticspectrograph Big Karl. The applied method ensures highaccuracy of the results, allowing to study of even quitesmall effects of the isospin symmetry breaking . In theprevious experimental runs the performance of new de-tection system was tested and it was shown that evenin the presence of a large background produced in theneighbouring beam dump region the detectors operatedvery well . In order to improve the particle separation anew scintillation hodoscope consisting of thicker detec-tors was constructed and mounted. With all the improve-ments done previously the detection system was ready tomeasure the goal reactions .

In the beam time allocated in fall 2000 we have suc-cessfully completed measurements for two beam mö-menta. The beam momentum of 1 .57 GeV/c correspondsto the 97 productionthreshold, where the symmetry break-ing effect should be maximal . For the second beam mo-mentum of 1.59 GeV/c the expected symmetry breakingeffect should be almost negligible . The 3He detected atthe Big Karl focal planewas clearly identifiedin the miss-ing mass spectrum shown in Fig. 2 . The observed back-ground is sufficiently low and would only slightly influ-ence the measured cross section . Due to the beam dumplocated very close to the 3H detection system, a some-what higher background was observed in the 3H spectra.However also in this case the 3H may be easily identifiedin the time of flight spectrum shown in Fig . 3 . For com-parison, the background not associated with the target isalso shown . We expect that precise off-line calibrationsof the detectors response will allow to reduce the back-ground to a lower level.

I

I

i

50 100 150 200 250MISSING MASS [MeV]

Fig . 2: Missing mass spectrum forp + d --3 3He+ .7r°

reaction measured for abeam momentum of 1.57 GeV/c.

0

100

Fig . 3 : Time of flight spectrum for the p + d -4 3H+7r+

reaction measured for abeam momentum of 1.57 GeV/c . Thebackground not associated with the target is shown as thedashed line .

The production of heavy mesons like the 77 meson onlight nuclei close to the threshold is connected with ex-tremely large momentum transfer [1] . Such momenta arebeyond the spectrum of Fermi momenta . It is, therefore,very unlikely that the meson is produced in a nucleon-nucleon interaction . Interaction has to take place eitheron a cluster of several nucleons or by multistep processes .Light nuclei have a pronounced cluster structure making

Exclusive 77 Production on Light NucleiThe GEM Collaboration

In addition a measurement of the relative acceptanceof the 3He/3H detections systems was performed . Thespecial feature of the p + p -> d + 7r+ reaction for theinvestigated beam momenta was used . At beam momentaclose to 1.57 GeV/c the ratio of maximum and minimumkinematically allowed deuteron momenta is about 2 . Thecentre of mass cross sections for these two situations areequal due to entrance channel particle identity. The si-multaneous detection of these deuterons simulate almostexactly the behaviour of 3He/3H for the goal experi-ment . In this way the relative acceptance of two detectionsystems was measured with good accuracy. This relativeacceptance includes not only the geometry of the detec-tion systems but also the absolute efficiency of the detec-tors .

The data analysis is in progress . However, alreadyfrom the very preliminary analysis we observe a verylarge symmetry breaking effect for the beam momentumof 1 .57 GeV/c, while such an effect is not seen at higherbeam momentum. In order to confirm the observationof the symmetry breaking and finally extract the mesonmixing angle measurements at a few beam momenta arenecessary. They will be performed in fall 2001 .

The results ofthe previously performed test measure-ments were reported in Ref.'s [2,3], as well as the modeldescription and results of the calculations in Ref.

[1] .The idea of the experiment and first results from the testmeasurements were presented in Ref. [4] .

References

[1] A . Magiera and H. Machner, Nucl . Phys . A 674(2000) 515.

[2] GEM Collaboration, Test measurement of Isospinsymmetry breaking in the p+d-+3H+7r+ and thep+d-+3He+7r° reactions, Annual Report KFA 1999(2000) 58 .

[3] GEM Collaboration, Background reduction meth-ods for Big Karlfirst dipole yoke detection system,Annual Report KFA 1999 (2000) 60 .

[4] A. Magiera for the GEM Collaboration, Isospinsymmetry breaking in p+d+3H+7r+/3He+7r° reac-tions, Verhandl . DPG (VI) 35,(2000) 229.

the first reaction mechanism likely . The production of rlmesons in the reactionp+'Li -+'Be+r7 was calculatedin a model, assuming an underlying p + d -+ 3He + 77reaction and treating the additional a-particle in the tar-get a a spectator [2] . The calculation were confrontedwith data from Ref. [3] . In this experiment r7-productionwas measured by detecting the two y's from its decay.The final results was eight events, but three out of them

were attributed to background. Such an experiment doesof course not allow to distinguish between different nu-clear states . The deduced cross section could only by ac-counted for by the calculation if one assumes that mostof the yield is due to excited states in the final baryonicsystem .

In the present experiment we follow an alternative ap-proach . Instead of measuring the rl-meson, which canonly be done with poor resolution, we tried to measurethe recoiling 7Be nucleus . A 6Li target with resolution

r

Fig . 2: Mechanists during assembling of the scintillators intothe vacuum box .

Fig . 1 : Top view of the AE-E detection system. The AE detector (top) is along barwith 0.5 mm thickness while the E-detector(bottom) consists offour bars on top of each other with 2mm thickness each. The light is guided to fast phototubes being installedoutside the vacuum .

The AE detector has a thickness of 0.5 mm, the E de-tector is 2 mm. The latter was divided in the vertical di-rection into four layers, thus allowing a modest positionmeasurement. It was found that the time information de-duced from the left and rightread out was not sufficienttodeducethe position with sufficient accuracy, although fast

of 1 MeV was applied . This restricts the reaction to theground state and first excited state . A feasibility run per-formed at 1 .297 MeV/c which is 3.08 MeV above thresh-old . Because of the high ionisation of the low energyheavy recoil in reaction all focal plane detectors have tobe in vacuum. As detection system we used a AE-E sys-tem made of plastic bars with the possibility of a 60 cmtime-of flightpath in between . The set up is shown in Fig .1 .

268

scintillating material as well as fast phototubes were ap-plied. The dimensions of the vacuum box are illustratedin Fig . 2.

The test run showed superb particle resolution. How-ever, because of physical background due to multi pionproduction as well as to a poor empty target run onlyan upper limit for the cross section with a rather largeerror could be deduced . In order to separate the differ-ent reactions the missing mass of the unobserved neutralmesonic system has to be measured . This will be done bymeasuring the momentum of the recoiling nucleus andits emission direction by two position measurements inthe focal plane. For thatpurpose two packs of multi-wireavalanche counters with two dimensional sensitivity willbe installed in front of the AE-counter for the next run .

References

[1] Gem collaboration, contribution in this report.[2] J . S . Al-khalili et al ., J. Phys. G19 (1993) 403 .[3] E. Scomparin et al., J . Phys . G19 (1993) L51 .

Measurement of Analyzing Powers and Spin Correlation Coefficientsfor Elastic pp Scattering

EDDA collaboration: M. Altmeier, J . Bisplinghoff, M. Busch, C. Dahl', 0. Diehl,H . P. Engelhardt, P. D.Eversheim, R. Groß-Hardt, F. Hinterberger, R. Maschuw, A. Meinerzhagen, 0. Ndhle, H. Rohdjeß, D. Rosendaal, V.

Schwarz, H. J. Trelle, K. Ulbrich, E. Weise, R. Ziegler (ISKP, Univ . Bonn)F. Bauer, K. Büßer, T. Colberg, L. Demir6rs, 0. Eyser, J. Greiff, E. Jonas, H. Krause, C. Lehmann, T. Lindemann,J. Lindlein, C. Pauly, N. Schirm, W. Scobel, A. Wellinghausen, T. Wolf (I . Inst. £ Exp. Physik, Univ. Hamburg)

0. Felden, R. Gebel, M. Glende,B . Lorentz, R. Maier, D. Prasuhn, P. von Rossen (IKP, FZ Jülich) .

IntroductionThe proton-proton elastic scattering is fundamental tothe understanding of the strong interaction. Excitationfunctions and angular distributions for cross sectionsand polarization observables of the pp interaction, inparticular the elastic channel, provide the data base forphase shift analysis serving as input to calculations ofeffective NN interactions in nuclei, and to test meson ex-change models . At present, the long and medium rangepart of the NN interaction seems to be well studied. Thedata are well represented by phase shift solutions andmeson exchange models . However, at higher energiesprecise data, especially of polarization observables, canbe useful to improve and extend phase shift analyses.

Experimental SetupThe EDDA experiment is designed to measure excita-tion functions of the unpolarized differential cross sec-tion dQ/dn[1], the analyzing power AN [2] and the spincorrelation parameters ASS, ANN and ASL with a highrelative accuracy over a wide momentum range from 1.0UP to 3.3 GeV/c.EDDA was conceived as an internal target experi-

ment using the recirculating COSY beam. Data col-lection proceeds during synchrotron acceleration in amulti-pass technique, so that a complete excitation func-tion is measured in each acceleration cycle. Statisticalaccuracy is obtained by averaging over many cycles .

Figure 1 : Scheme of the EDDA detector .

The EDDA detector (shown in Fig. 1) was designedto provide a fast trigger for coplanar two-prong events(i . e. fit - -I)1 = 180,) that fulfill the kinematic corre-lation of elastic pp scattering . It consists of two cylin-drical hodoscope layers with a large solid angle coverage(35° < Ge.m . < 90°) . The inner layer (H) is composedof scintillating fibers which are helically wound in op-posing directions around the beam pipe in four layers .The outer layer consists of scintillator bars (B) which arerunning parallel to the beam axis ; they are surroundedby scintillator semi-rings (R) .

59

Analyzing power

Figure 2: The polarized atomic beam target .

For the measurements of the analyzing power andthe spin correlation coefficients a polarized atomic beamtarget (see Fig. 2) was used . The polarization is pre-pared with two permanent sixpole magnets and an RF-transition unit . The direction of the polarization inthe interaction region is aligned with' a magnetic guidefield of about 1 mT. Thetarget thickness was 1.8 . 1011atoms/cm2 resulting in a luminosity for the analyzingpower measurements of 8 - 1027 cm-2 s-1 and about oneorder of magnitude lower for the spin correlation mea-surements . An effective polarization of 70-75% could beachieved . The atomic beam has a diameter of 12 mm(FWHM). The resolution of the vertex reconstruction -obtained by a kinematic fit to the points of incidence ofinner and outer layer - is better than 2 mm.

The analyzing power was measured using the polarizedatomic beam target and the unpolarized COSY beam .The measurements were performed in cycles of about13 s duration . The direction of the polarization waschanged cyclewise from +x to -x, +y and -y. Theanalyzing power is determined from top-bottom (left-right) count rate asymmetries for a target polarization inx (y) direction. The absolute target polarization valuesare established by normalizing the observed asymmetryfor one momentum bin Op = 60 MeV/c around theenergy of 730 MeV to a precise angular distribution ofthe analyzing power from McNaughton et a1 .[4] .

Results with different polarization states were com-bined to apply a correction for false asymmetries [5].The largest systematic error arises from inelastic reac-tions that accidentally fulfill the signature of elastic ppscattering . The remaining background was estimated,guided by Monte Carlo simulations, to be mostly < 2%and only at highest energies and most backward anglesup to 4.5 %.

Excitation functions with about 850 datapoints havebeen deduced and are published [2] . The comparisonto the recent phase shift solutions of the VPI groupSAID SP99 [3] (not including our data) shows (see Fig. 3)agreement in the general size and momentum depen-dence , but also systematic deviations in the momentumrange 1800-2500 MeV/c, where other data are scarce.This discrepancy is reduced for the SAID solution FA00,which does include our data and results in lower valuesof x2 per datum.

za 0.60.50.40.30.20.10

0.60.50.40.30.20.10

-0.110001500 2000 2500 3000

1500 2000 2500 3000p(MOVlo )

Figure 3: Four out of 12 excitation functions of the ana-lyzing power AN for Lip = 60 MeV/c and DO,.,, . = 5°bins . Also shown is the solution from the phase shiftanalyses of the VPI group [4] SAID SP99 .

Spin correlation coefficientsThe spin correlation coefficients Ass, ANN and AsL aremeasured using the polarized atomic beam target andthe polarized COSY beam. The target polarization ischanged with every cycle between =Lx, -4-y and fz. Thebeam polarization is changed cyclewise from +y to -y,thus 12 different combinations of polarizations result .

Because of the 41)-dependence of the polarized differ-ential cross section, one obtains a modulation of countrates depending on the polarization configuration. Foranalysis the detector is divided in four 4~-segments (cen-tered at 45°, 135°, 225° and 315°) . The -1)-dependenceo£ the cross section leads then to count rate asymme-tries in the four sectors that can be used to determinethe spin correlation coeicients as well as the target andbeam polarization if the analyzing power is known. Herewe used our results [2] .A first measurement was carried out at a momen-

tum (energy) of 1430 MeV/c (772 MeV). This is thehighest energy in the energy range of COSY where datafor all three spin correlation coefficients from other ex-periments exist. Our data are in good agreement withthe other data as well as the phase shift solution FA00,showing that the determination of the spin correlationcoefficients works (see Fig. 4) .

60

M

4,0 .5

0

-0.5ZZa 0.5

0

0

-0.5

Figure 4: The spin correlation coefficients ASS, ANNand ASL at 1430 MeV/c. Closed symbols, this experi-ment; open symbols, experiments at LAMPF and SAT-URNE ([7-9]) . The SAID solution FA00 is given as asolid line.

Subsequently, the measurements have been extendedto higher energies . Data collection proceeds during beamacceleration andthe following flat top. The result from aflat top measurement at 3100 MeV/c is shown in Fig. 5.In this energy range no data for ASS and only few datafor ASL existed previous to our measurements . Otherdata exist only for ANN, which are in good agreementwith our measurements . Also shown are predictionsof phase shift analyses of the VPI [3] and the Saclay-Geneva [10] group. From the Ass results, the limitedpredictive power of phase shift solutions not sufficientlysupported by experimental data can be seen.

Ul

~-Ck"0.5

-0.5z0 .5

0

-0.5

Na 0.5

0

-0.5

30 40 50 60 70 80 90

8.m (dog)

----------------------

4

EDDA protImlnaryQ SATURNE-

SAID FADS,-

PSA SG (S200 Mayla)

p=3100 McVlc

J9.0aQ©

---------------------------------------------------------------

v

v

v

v

30 40 so 6070 80 90

ecm (dog)

Figure 5: The spin correlation coefficients Ass, ANNand AsL at 3100 MeV/c. The SAID solution FA00 iEgiven as a solid line, a solution of the Saclay-Genevaeyrnnn fl 01 at .3200 MW Jc a4 the dashed line .

" EDDAprrollmlneryA LAMPF McVlc[3 SATUHNE

p=1430- SAID FADS

-------------------------------------------------------------- -

---------------------------------------------------------------

O~m °=42.5 O= °= 52.5

k

Ocn, °=62.5 O~, = 82.5 °

0.5

0

-0.5

Acknowledgements

n,- 45

-----------

- - -- - -

ö .a_

.Q ~. .r

Measuremerit during! accelerbtiori (prellnilnery)Measurements atfixed energies (prellmi6ary)SAID FA00

L-L9' -'-f .'. L.1 . L . . , 1

1

' : lI . . . .̀1 1 1

In Fig. 6 excitation functions for 0,,. = 450 of thethree spin correlation coefficients Ass, ANN and ASLare shown. These data have been collected during beamacceleration and show no systematic deviations from ourflat top measurements .

The measurements will be continued with differentflat top energies so that the momentum range above2500 MeV/c, where the differential cross section for theelastic proton-proton scattering is low and the statis-tics of the excitation functions are insufficient, will becovered .

The EDDA collaboration gratefully acknowledges thegreat support received from the COSY acceleratorgroup. This work is supported by the BMBF and bythe Forschungszentrum Jiilich.

References

Figure 6: The spin correlation coefficients ASS, ANN and ASL measured during beam acceleration (empty symbols)with lip = 60 MeV/c and AO =10°. Also shown are results from our flat top measurements (solid symbols) and theSAID solution FA00 (solid line) . Depolarizing resonances are indicated by the dotted lines.

[1] D. Albers et al . Phys . Rev. Lett. 78, 1652 (1997) .[2] M. Altmeier et al . Phys . Rev. Lett. 85, 1819 (2000) .[3] R. A. Arndt et al . Phys. Rev. C 62, 034005 (2000),

SAID solutions SP99 and FA00 .[4] M. W. McNaughton, et al. Phys . Rev. C 41, 2809

(1990) .[5] G. G. Ohlsen andP.W. Keaton Nucl. Instrum. Methods

109, 41 (1973) .[6] W. R. Ditzler et al . Phys. Rev. D 29, 2137 (1984) .[7] J. Bystricky et al . Nucl . Phys . 13262, 727 (1985) .[8] G. Glass et al. Phys . Rev. C45, 35 (1992)[9] A. de Lesquen et al . Nucl. Phys. B304, 673 (1988) .

[10] J. Bystricky, C. Lechanoine-Leluc, and F. Lehar Bur.Phys . J. C4,607 (1998) .

F. Belleinann', A . Berg', J . Bisplinghoff , G .Bohlscheid', J . Ernst', F . Hinterberger', R . Ibald',R . Jahn', L . Jarczyk2 , R . Joosten', A. Kozela3 , H . Machner, A. MagieraZ, R . Maschuw',

T . Mayer-Kuckuk', G. Mertler', J.Munkel', D . Rosendaal', P . v . Rossen,H. Schnitker', J. Smyrski2 , A . Strzalkowski2, R . T611e, and C. Wilkin4

The MOMO experiment focuses on near thresholdmeson production via the reactions pd -> 'He 7+z andpd -> 'He K+ K. It takes advantage of the high qualityof the cooled external COSY beam and the existingspectrometer BIG KARL. The setup consists of a highgranularity scintillating fibers meson detector near thetarget with a ± 45 deg . opening angle, and the spectro-meter, which is used for 'He-identification . The largesolid angle and high resolution ofthis detection methodwill yield precision data on the low energy (T<80 MeV)meson-meson interaction and probe into questions likemeson-nucleon resonances and KK-molecule .

The MOMO vertex detector consists of 672 scintillatingfibers (round, 2.5 mm diameter) arranged in threeplanes tilted 60 deg . versus each other. Each plane issubdivided into two identical modules . The fibers areread out by 16-fold photomultipliers . The totalefficiency was measured to be better than 99% forminimal ionizing particles . The BIG KARLspectrometer is also fully operational. Its status isdescribed in detail elsewhere in this annual report . TheMOMO scattering chamber houses the 4mm LDZ targetas well as a remotely steerable ladder for beam viewersand solid targets . The 5 mm thin Al front end of thechamber faces the vertex detector on the outside andkeeps straggling of the mesons at a small level.

Until 1997, the MOMO collaboration measured the pd-> 'He -n'Tc reaction at three different proton beammomenta (1060 MeV/c, 1150 MeV/c, 1200 MeV/c),corresponding to 28 MeV, 70 MeV and 92 MeV centerof mass energy above the reaction threshold . In total,some 30 000 kinematically complete nn- - events wereobserved . The obtained two - pion invariant massspectra showed a strong deviation from phase space atall three energies, whereas the 7C - 3He missing massspectra followed phase space . The pion angulardistributions displayed a remarkable sidewise peaking(in the c.m.s .) and. a preferential back to back emissionof the two pions . his behaviour can be well describedby calculations assuming a p-wave between 'the twopions and s - waves in the 7c - 3He system .

Subsequently, the MOMO - collaboration measured twokaon production via the reaction pd -> 'He K+ K atbeam momenta of 2.585 GeV/c and 2.620 GeV/c (Q =40 MeV and 56 MeV, respectively) . The beam intensitywas about 5 x 10$/s with a cycle of 12 s - 20 s beam onand 8 s beam off. Furthermore, for the beam halo wasnegligible (< 10'a) . The count rate of the implementedhalo veto counter was only some 80 K/s .

At both energies the reaction pd --> 'He K+ K7 wasmeasured at four largely overlapping BIG KARLmomentum settings, so that the full phase space of the

Results on Two - Kaon Production at MOMO

62

reaction was obtained . The 'He - particles could beunambiguously identified by time of flight and energyloss measurements . The two - kaon hits on the vertexwall were uniquely identified by their hit patterns andenergy loss . Good events must be coplanar in respect tothe total meson momentum axis, which is defined by thebeam and the 'He momenta . The newly implemented 16- fold circular scintillator hodoscope behind the vertexdetector enables good kaon identification and pionseparation . In total, some 4000 two kaon events wereobserved . The results of our data analysis are displayedin the figures .

0.2

oL0

.i

i5 10 15 20 25 30 30 40 as

Tee t AMU 1Fig . 1 : K+K" invariant mass spectrum from the reactionpd --> 'He K+ K at 40 MeV above reaction thresholdplotted in units ofK+ K' relative energy.

Fig . 1 shows the obtained two kaon invariant massspectrum at Qxx = 40 MeV, 8 MeV above the ~ -theshold . A clear signal ofthe ~ - meson is evident . Fig .2 and fig. 3 show the kaon angular distributions andfig .4 the kaon - helium invariant mass spectrum. In allfigures, the dashed lines correspond to phase space . Incontrast to our two pion data, no significant deviationfrom phase space (plus ~ - production) can be observed .The bump in the relative angle spectrum (fig .3)originates from kaons arising from ~ - decay, sincethese events are limited to a maximal possible relativeangle determined by reaction kinematics .

Fig . 5 shows the KK invariant mass spectrum at QKic =56 MeV ( Qm = 24 MeV). Again, the data follow phase

space including a clear - peak. The obtained crosssections are :

Qxx = 40 MeV :

9.6 ±

1 .0 nbQK c= 56 MeV :

17.5 ±

1.8 nb

Q~=8MeV : 0.9±0.2nb

Q~ = 24 MeV :

1 .4 ± 0.6 nb

The Q - dependence of these cross sections scales wellwith the assumption of s - wave two kaon and ~ -production. It is interesting to note, that no indication ofp - waves is present in these data, in contrast to our twopion data, where a p - wave dominance was observed .In Feb. 2001 data will be taken at Qxx = 34 MeV whichisjust 2 MeV above the ~ = production threshold .

.öcY

uvwbv

ä

VHQu

äb

cos(AK)Fig 2 : Angular distributions of the individual kaons inthe c.m.s . at 40 MeV above threshold .

cos(3.)

Fie.3 Distribution of the relative angles between thetwo kaons in the c.m.s . . See text .

63

Üwa5

bn

,5, O.sOl,? 0.7.Dc 0.6

+Y 0.5f-T)b 0.4

T��, I MeVFig . 4 : K - 'He invariant mass spectrum from thereaction pd -a 'He K' K7 at 40 MeV above reactionthreshold plotted in units ofK - 'He relative energy .

0.3

0

TOW- I M eV J

Fig. $ : K+K invariant mass spectrum from the reactionpd __> 3He K+ K' at 56 MeV above reaction thresholdplotted in units of K' K" relative energy .

Institut feir Strahlen- und Kernphysik, UniversitätBonn

2 Institute of Physics, Jagellonian University,

Cracow,Poland

'Institute ofNuclear Physics, Cracow, Polanda Physics & Astronomy Department, University CollegeLondon, UK

64

1 .2

Experiments at External Facilities

ATRAP, after half a year of operationfor the ATRAP-Collaboration: D . Grzonka, W.

Since July 2000 the Antiproton Decelerator AD atCERN delivers 3 . 107 antiprotons per bunch deceler-ated from the injected 3.5 GeV/c down to 100 MeV/c.The beam is extracted with a pulse width of about 300ns each 90 sec. ATRAP (see [ATR97]) is one of the 3running experiments sharing the available beam time inequal parts.

In phase I of ATRAP which is the actually used ver-sion (see [ATROOa]) a system of several consecutive pen-ning traps of 1.2 cm diameter and a total length of 30cm are placed in the bore of a very homogeneous 6 Tmagnetic field of a superconducting magnet . The trap-ping region is surrounded by the Jülich fibre detector[ATR99] placed inside the bore of a diameter of 10.5cm and by two layers of scintillator paddles outside o£the magnet . After calibration, relative efficiency andMonte Carlo studies for the scintillation detectors abso-lute numbers of trapped antiprotons can be given. Forthe detection of the positrons via the 511 keV gammmsin November 2000 a BGO-detector consisting of a ringof 12 crystals between the trap and the fibre detectorwas added and included in the article detector system .First data of this gammadetector have been taken whichshowed that an improvement of the signals is necessaryby an optimization of the light output .

The first month of operation were dedicated to thestudy of the optimal settings of the trapping systemwith respect to particle capture and hold times. Theseand the necessary moving of the trapped particles intospecial regions were continuously controlled . By the de-tection of the p annihilation products (see[atr00b]) thelosses of particles in different steps ofthe procedure weremonitored . The losses of trapped particles are due toheating during potential changes or randomly due tostatistical fluctuations or imperfections of the poten-tials . Already after the first days of beam operationthe ATRAP experiment trapped a few hundred p's pershot which could be optimized to almost 10000 p's pershot . ATRAP also succeded in electron cooling of thetrapped P's which was proven by the detection of the an-nihilations after opening the potential well which couldhold only P's with an energy below 4.8 eV. Fig. 1 showsthe procedure of measuring the energy distribution oftrapped p. The depth of the potential well filled withp is reduced by increasing the negativ electrode poten-tial towards zero within a linear ramp (upper left part) .The detected annihilations which are proportional to theCounts in Fig. 1 as a function of the electrode potential(lower part in Fig. 1 ) correspond to the energy distribu-tion of the trapped p.

Another important step towards cold antihydrogenwas done by accumulating cold positrons from a strong(-150 mCi) "Na source . In about one hour two millionpositrons could be accumulated. In first studies of theinteraction of the trappedp with the e+ afurther cool-ing of the antiprotons by overlapping the two particleclouds could be detected (see Fig. 2) . The spectrumof the antiprotons after interaction with the positronsis shifted to lower energies compared to the antiproton

67

Oelert, G, Schepers, T. Sefzick

Figure 1 : Plots out ofthe ATRAP-logbook showing theenergy spectrum of the antiprotons released from thetrap by lowering the potential in a controlled way.

Figure 2: Energy spectrum of the antiprotons after theinteraction with the cold positrons

spectrum without trapped positrons and has anarrowerdistribution .

References[ATR97] Proposal ofthe ATRAP collaboration, CERN-

SPSC 97-ß/P306 .

[ATROOa] ATRAP II, this report.

[ATR99] Jülich fibre detector, Annual Report 99

[ATROOb] Monte Carlo studies for ATRAP, this report .

Preparation .of the Second Phase for theATRAP - Experiment at the AD/CERN

J . Bojowald, D. Grzonka, H. Hadamek, R. Nellen, W. Oelert, U. Rindfleisch, G. Schepers,und W. Erven, H. Gorke, P. Wiistner, K . Zwoll (ZEL - FZ-J)

for the ATRAP - collaboration at the AD/CERN

The activity of the ATRAP [1] collaboration atthe new Antiproton - Decelerator AD is focusedto the great challenge of comparing properties ofhydrogen and antihydrogen to high accuracy . Thecurrent assumption, that reality is invariant underCPT transformations, is based in large part upon thesuccess of quantum field theories, which themselvesrely on reasonable presumptions as causality, localityand Lorentz invariance . Theoretical investigationsof possible CPT violations are now beginning toappear in the context of string theory [2] . ATRAPis prepared to contribute to these fundamentalquestions from the experimental side .

During the year 2000 measurements have beenperformed, are described in the present annual re-port [3] and were considered as successful steps to-wards the production of cooled antihydrogen . Thesefirst tests were done using an available superconduct-ing magnet, which were necessary for both a start-upof the experimental program and a learning proce-dure of the features at the new facility. Using theexperience gained the collaboration now developesthe second phase of the experiment .

The new superconducting magnet, shown inFig. 1, leaves much more space for the trap and thedetectors by having a central bore of N 0.5 meterdiameter . This space will be used differently indifent stages . First a rather small trap will be usedwith cylindrically arranged layers of detectors madeout of Si-fc-strip and scintillating fibers . This set-upis optimized for tracing back the location of antipar-ticle annihilation with normal matter . During thistime the collaboration has to learn how to handlethe electro-magnetic fields provided by the overlayof the magnetic field and the static potentials at thedifferent electrodes of the trap, in order to keep theonce produced antihydrogen as much as possible atthe centre of the trap . Afterwards - as a secondstep - the inner detector layer will be taken outfor allowing more space for a larger trap in orderto gain production efficiency . In the final stagemost of the space available will be used for theantihydrogen-trap, surrounded by a trap for neutralparticles with a strong magnetic field gradient anda system of mirrors for the precision spectroscopy .

It is the contribution of the Jiilich group to theATRAP collaboration to provide the Si-ju-strip de-tectors and the three cylinders of scintillation fiberswith straight and helical orientation . In addition,

the superconducting magnet will be surrounded bytwo layers of 24 outer scintillation paddels for triggerpurposes . The design of these elements has started.

68

T. Sefzick (IKP - FZ-J)

Figure 1: The superconducting magnet with the trapand detector systems.

References[1] Proposal of the ATRAP collaboration, CERN-

SPSC 97-8/P306

[2] J. Ellis, N.E . Mavaromatos and D.V . Nanopou-los, Phys . Lett . B 293 (1992), 142V. Kostelecky and R. Potting, Phys. Rev. D 51(1995) 3923

[3] see two further contributions of the ATRAP -collaboration in this Annual Report 2000

Monte Carlo studies for the ,y detector atD. Grzonka, W. Oelert, G. Schepers, T.

for the ATRAP collaboration

The antihydrogen trap experiment ATRAP[ATR97], [ATR00] for the high precision spectroscopyof the antihydrogen atom is performed in two stages . Inthe first stage, ATRAP-I, where the trapping of p ande+ was studied, an existing superconducting magnetwas used resulting in a very restricted space for detec-tor components . Only one ring of scintillating fibresconsisting of 3 fibre layers (one straight and 2 helical)and a ring of BGO crystals combined with scintillatorpaddles surrounding the magnet could be installed. Inthe second stage, ATRAP-II, a new magnet will beused with sufficient space for the experimental com-ponents needed for the planned antihydrogen studies .Concerning the detection of the annihilation products,several layers of Si-y-strip and scintillating fibres andone layer of -1-detection crystals will be installed .

For both setups the -/-detection system has beenstudied by Monte Carlo calculations using GEANT 3.21including the FLUKA package [GEA94] for hadronic in-teractions .

Compared to a pure pp annihilation the annihilationat a copper nucleus of the trap wall induces much moresecondaries . Especially the high energy y's resulting inpositrons from the pair production of their interactiondisturb the identification of the primary positrons fromthe antihydrogen atom. Due to this secondary positronsan unambiguous identification of an antihydrogen atomon a single event basis is not possible . In order to extractthe optimum Ho-signal and to optimize the segmenta-tion of the -y-detector for ATRAP-II, MC data with apure p and e+ annihilation as well as data with a coin-cident annihilation of p and e+ have been produced .

At ATRAP-I the y detector consists of 12 single 12cm long BGO crystals with a trapezoidal cross sectionbuilding a tube with an inner diameter of about 5 cm.For each BGO crystal energy spectra are produced fromthe MC events (the energy resolution of the detector isnot included for a clear identification of the 511 keVphotopeak) . The energy spectra of pevents show an ex-ponential distribution in the low energy part with a 511keV photopeak and the spectra of the e+ events give thetypical -1 spectra with the photopeak at 511 keV and thedistribution of Compton scattered y's. A comparison ofthe pspectrum with the Ho spectrum shows an enhance-ment in the 511 keV peak by a factor of about 2 . Takingthe energy resolution of the detectors into account thisenhancement will be reduced to about 30 % due to theexponential distribution in the low energy part of thespectrum . Nevertheless such an enhancement will be aclear signal for the Ho annihilation .

Starting point for the -y-detector studies for ATRAP-II was a 2 cm thick tube with an outer diameter of 50cm and a height of 20 cm, cutted into 20 rings each di-vided into 64 0-segments . A comparison of the 511 keVphotopeak for pure p with a Ho annihilation shows anincrease ofthe events by a factor of 2 .4 . Also here the en-hancement will be drastically reduced using the realisticdetector resolution . Therefore it would be favourable to

69

Sefzick

ATRAP

Table 1 : Number of events in the 511 keV photopeakfor pure p, pure e+ and coincident p and e+ events . Inthe third row the uncorrelated sum of p and e+ eventsis given and the fourth row gives the ratio of the eventsfrom a coincident generation of p and e+ and to theevents from the uncorrelated sum . The ratio is 1 if thee+ annihilation is not influenced by the p annihilationand is reduced for an additional energy loss in the sameelement due to the p annihilation . Ratios larger than 1result from statistical fluctuations .

use scintillators with higher energy resolution like LSOinstead of BGO . In table ?? the number of events in the511 keV photopeak for pure p, e+ and for coincident p-and e+ events is given for different segmentations pro-duced by summing up the energy deposition of severalelements for each event. Given are the numbers for asingle detector element and the sum of 10 neighbouringelements in one column, 20 elements in one column, 2neighbouring columns (40 elements), 3 columns (60 ele-ments) and 4 columns (80 elements) . Up to 40 elementsthe ratio is about 1 which means that a ring of 32 scin-tillator bars is sufficient to detect the 511 keV y's fromthe positron decay without disturbance by secondariesof the p annihilation, a further reduction of the segmen-tation results in losses due to increased probability foran additional energy loss from secondary particles of thep annihilation .

References[ATR97] Proposal of the ATRAP collaboration, LERN

SPSC 97-8/P306K .

[ATR00] ATRAP contributions in this Annual Report .

[GEA94] GEANT - Detector description and simulationtool, CERN W5013,1994

elementscolumns

1 10 20lc

402c

603c

804c

p 7 39 65 80 94 104e+ 2.8 29 51 107 164 220p+e 10 72 108 191 227 250uncor. E 10 68 116 187 258 324ratio 1 . 1.06 0.93 1 .02 0 .88 0 .77

Measurement of the photon response of PbW04 and CeF3 below 1 GeV

The proposed photon detector for ANKE [1] will belocated in the target region in front of the dipolemagnet D2 [2]. Limitations in space require the useof a scintillator material with a radiation length assmall as possible .In recent years PbW04 has been investigated as ahigh-density inorganic scintillator with good energyresolution for photon detection even at intermedi-ate energies [3]. For high-energy physics it has beenchosen by the CMS collaboration at 'CERN as thematerial for the electromagnetic calorimeter (about80000 channels).

Table 1: Relevant physical properties for PbW04 andCeF3 .

Recent tests at the photon beam line of the electronaccelerator MAMI at the nuclear physics institute ofthe University of Mainz have been performed in orderto evaluate the photon response of PbW04 and, forthe first time, of CeF3. Both test arrays have a lengthof at least 16 radiation lengths and a diameter of atleast 3 Moliere radii . The properties of both materialsare shown in table 1.Figure 1 shows the resolution of PbW04, which isbetter than of CeF3 (fig . 2) despite its lower lightoutput . However, the CeF3 crystals (provided by theCrystal Clear Collaboration and ETH Mrich) areprototypes [4] and are not yet optimized like PbW04(manufactured by RI&NC, Minsk, Republic of Bel-raus, and Bogorodistsk Techno Chemical Plant, Rus-sia) . The CeF3 modules consist of 2-4 single crys-tals and the optical quality differs a lot; some mod-ules are, therefore, very inhomogeneous. The scin-tillation performance of PbW04 has been steadilyimproved by the raw material, crystal growth con-ditions and suitable dopants (Nb/La) to guaranteeradiation hardness .In fig. 1 a comparison of PbW04 with the existingBaF2 modules of the TAPS spectrometer is shown.The two curves correspond to an integration eitherover the total light output or over the fast compo-nent only. BelowE. y=300 MeV the resolution is dom-inated by the low light yield of the scintillator, butat higher energies the performance gets better dueto the high density and short radiation length .The time resolution (achieved by selecting an im-pact point between two neighbouring crystals) isat = (1/v"2) - 237 ps = 168 ps and at = 130 ps

R.Beckl, W.D6ring2 , V.Hejny, R.Novotny2, K.Römer 2

70

b

12

Oil

References

Figure 1: Preliminary test results on the resolution ofPbW04 as obtained in August 2000 at the electronaccelerator MAMI of the University of Mainz.

10

9

6

6

s

0 100 200 300 400 500 E00 e00 800photon energy /MeV

Figure 2: Preliminary results on the resolution ofCeF3-

for CeF3 and PbW04, respectively.Radiation resistance has been investigated by theCMS collaboration [5], where this problem is moresevere than at COSY . It was found, that the loss inlight output due to radiation damage saturates atabout 5% at high neutron rates.All these properties together make PbW04 mostsuitable for use in a future electromagnetic calorime-ter at ANKE.

[1] M. Büscher et al ., COSY Proposal #83: A pho-ton detector for COSY, November 2000.

[2] M. Büscher et al ., contrib. to this Annual Re-port .

[3] R. Novotny et al ., IEEE Trans. on Nucl. Sc . 47(2000) 1499 .

[4] E. Auffray et al ., Nucl . Instr. and Meth. inPhys .Res. A 378 (1996) 171 .

[5] E. Auffray et al ., Proceedings of SCINT99,Moscow, Russia .

1 Institut für Kernphysik, Universität Mainz2 Il . Physikalisches Institut, Universität Gießen

PbW04 CeF3density p [g/cm 3] 8 .28 6 .16index of refraction 2.16 1 .68radiation length Xo [cm] 0.89 1 .68MoRre radius RM [cm] 2 .2 2 .6major decay constants [ns] < 20 30peak wavelength [nm] 420 310-340temp . dep. of light yield [%/°Cj F~,, -1.9 -

The measurement of the hadronic shift and broadeningof the ground-state in pionic hydrogen gives access tofundamental properties of the pion-nucleon interaction.Ongoing improvement in the calculation of strong-interaction phenomena by Heavy-Baryon Chiral Pertur-bation Theory allows predictions with an accuracy of afew per cent, which should be experimentally tested[1,2] .

Newly developed techniques for the precision spectros-copy of X-rays from antiprotonic hydrogen [3] as wellas for the determination ofthe charged pion mass [4] areproposed to use for a new series of measurements [5,6] .The aim is to achieve finally an accuracy for the hadro-nic broadening rl. of about 1%, which is an improve-ment of almost one order magnitude as compared toprevious precision experiments [7]. The measurementswill also yield a better value for the hadronic shift sl g .

First goal of the new experiment is to establish a shiftvalue independent of pressure. Such a pressure depen-dence would originate from the formation of complexmolecular structures like [(7Epp)p]ee [8] . The 7160 (6h-5g) transition, which is not affected by the strong inter-action, serves as energy calibration. At lower pressures,a simultaneous measurement of both the hydrogen 3p-lsand the oxygen line is possible. This allows an energycalibration basically free of systematic errors. At higherdensities, hydrogen and oxygen measurements have tointerleaf each other.

In autumn 2000, an engineering run took place at thenE5 high-intensity pion channel at the Paul-Scherrer-Institut (PSI) . The experimental set-up is similar to theone used for the pion mass measurement [4] . As target,a cryogenics system was installed in the center of thecyclotron trap, where about 1% of the incoming pionsare stopped in gas at normal temperature and pressure.Higher densities are achieved by cooling, because ofthelow X-ray energies thin windows have to be used . TheX-rays were reflected in first order by a spherically bentsilicon Bragg crystal cut along the 111 plane . To keepaberrations small, the crystal was covered by an aper-ture restricting the reflecting area horizontally to60 mm. As X-ray detector served again the large-areaarray ofCharge-Coupled devices (CCDs).

At a gas density of 3.5 bar equivalent, with a gas HZ/OZmixture count rates of about 20 per hour were achieved(Figure 1) . The peak-to-background was improved si-gnificantly compared to the previous experiments . Intotal, 750 and 1100 events were recorded in the oxygenand the hydrogen line . This already yields an accuracyfor the shift which is slightly better than that of earlierresults because of the absence of sytematic errors in theenergy calibration. A preliminary value for the shift is

el , = 7.080 ± 0.035 eV (attractive),

Pionic hydrogen

D. F. Anagnostopoulosa, G . Borchert; W. Breunlichb , M. Carfnellib, H . Fuhrmannb, D. Gotta, M. Gierschb, A. Gruberb ,M. Hennebach, P . Indelicato°, T . Jensen",', Y.-W. Liu , B . Manf°, J. Martonb,V. Markushin, N. Nelmsg,

L. M. Simonsf, H . Zmeskalb

71

which is in agreement with the previous experiment(7.102±0.038 eV [7]) .

The response function of the spectrometer was obtainedfrom the nl2C (5g-4f) transition, which is close in ener-gy (2973.82641 keV). The energy levels involved hereare also not affected by the strong interaction .

From the limited statistics of the engineering rim, noconclusions can be drawn on density effects yet. Thehigh-statistics run for the shift is foreseen in summer2001 . Further measurements will investigate in detailthe pressure dependence of the line widths of variouspionic hydrogen transitions to establish the pure hadro-nic effect with the envisaged accuracy .IM .~ . .... ... .

9`!tt

2.880506 keVn160 (6h -59)

nH (3p -1 s)2.686 keV

Still

H2/02(95%/5%)3.5 bar equivalent

K:::.

. .~ :'.~:. ,

.. . . .

.. .

,

-

. . . . . . ....

.. ...

_ .

. .

;;«? .. .

..-,16l)

'(81

i 0

2110

24

Figure 1 . Simultaneously recorded reflections of the7c0(6-5) calibration transition and the 7H(3-1) transition . The spectrum displays about 1/3 of the total stati-stics accumulated for the HZ/OZ mixture .

[1] A. Rusetsky, in Frascati Phys. Series, Vol . XVI,1999, ISBN 88-86409-21-4, p . 669, and ref, therein

[2] N. Fettes et al ., Nucl . Phys. A 640 (1998) 199[3] D. Gotta et al., Nucl. Phys . A 660 (1999) 283[4] Precision measurement ofthe mass of the charged

pion, this report[6] D. Gotta, 7rN newsletter no . 15, Dec. 1999, p. 276[5] PSI experiment R-98.01[7] H.-Ch. Schr6der et al ., Phys . Lett. B 469 (1999) 25[8] S . Jonsell et al. Phys. Rev . A 59 (1999) 3440

'Dept . of Material Science, Univ. of Ioannina, Greeceb Institut für Mittelenergiephysik, Osterr. Akademie derWiss., ViennaLab . Kastler-Brossel, Univ . P. e t M. Curie, Paris

d Aarhus Univ., Danmarke ETH Zürich, Switzerlandf Paul-Schemer-Institut (PSI),Villigen, Switzerlands Dept. ofPhysics and Astronomy, Univ.of Leicester

D. F. Anagnostopoulosa, G . Borchert, J.-P. Egge?, D. Gotta, M. Hennebach, P . Indelicato° , Y.-W . Liud, B . Manil°,N. Nehn?, L . M. Simonsd

A series of experiments to determine the mass of thenegatively charged pion was finished by a high-statisticsmeasurement in summer, 2000 [1,2] . Here, pionic andmuonic transitions from nitrogen and oxygen were mea-sured. The muonic line served as energy calibrationbecause the muon mass is known to more than one orderof magnitude better than the pion mass [3] . The circulartransitions, 7rN(5g-4f) and p.O(5g-4f), are not affectedby finite-size effects and hence not distorted by stronginteraction . Furthermore, using dilute targets, electronrefilling is suppressed, thus avoiding any energy shiftsfrom satellite transitions .

The pion beam of the 7rE5 channel at PSI was injectedinto the cyclotron trap II [4], the basic idea of which isto wind up the range curve in a weakly focusing ma-gnetic field . In the case of pions, deceleration has to befast because of the short life time . The energy loss of thepions is then achieved by thick degraders. About 1% arestopped in a thin-walled gas-filled target container in thecenter of the trap at a pressure of 1 .4 bar. Length anddiameter of the gas cell are 220 mm and 60 mm, re-spectively. Muons, originating from pion decay shortlybefore capture, are slow enough to be stopped in the gascell as well . With a set-up, optimized for muons, thecount rate for muonic atom X-rays is about 4% of theone for pionic atoms . Because of the high pion flux ofseveral 109/s, this method is still superior to a direct useofa muon charmnel .

The X-rays were reflected in second order by a spheri-cally bent silicon Bragg crystal cut along the 110 planeand having a radius of curvature of 2.985 m. The X-rayswere recorded in a newly set-up large area detectorarray of 20 Charge-Coupled Devices (CCDs). Thesensitive area of one chip is 24 nun x 24 mm or 600 x600 pixels of 40 um [5] . CCDs allow an efficient back-ground reduction by analyzing the hit pattern and ap-plying simultaneously a narrow cut on the depositedcharge . Such an analysis is essential for low-rate ex-periments in accelerator environments [6] .

The aim of the experiment is to reach an accuracy ofabout lppm for the mass of the charged pion, whichrequired the accumulation ofabout 10000 events in eachof the two lines in a running period of several weeks .With a count rate ofabout 15 per hour and transition byusing an NZ/OZ gas mixture of 90%/10%, the simultane-ous detection of both lines (Figure 1) inherently avoidssystematic errors arising from the long-term stability ofthe experimental set-up .

After correcting for the curvature of the image, the re-flections are projected to the axis of dispersion (Figu-re 2) . The distance between the pionic and the muoniclines results in the ratio of the masses of the pion andthe muon.

Precision measurement of the mass of the charged pion

72

Figure 1 . Simultaneously recorded reflections of the5 - 4 transitions in 7rN and gO using a silicon crystal of90 mm diameter. The sensitive area of the CCD array(not drawn in scale) is 48 nun x 72 mm.

Figure 2. Projection of the 7rN and p,0 reflections to theaxis ofdispersion .

a Dept . ofMaterial Science, Univ. of Ioannina, Greeceb Inst. de Physique de 1'Univ.de Neuchätel, Switzerland'Lab. Kastler-Brossel, Univ. P . et M.Curie, ParisdPaul-Scherrer-Institut (PSI), Villigen, SwitzerlandDept . ofPhys . and Astr ., Univ. of Leicester, England

[1] PSI experiments R-94.01 and R-97.02[2] S . Lenz et al., Phys . Lett. B 416 (1998) 50[3] D.E. Groom et al . (PDG) Eur. Phys. J. C 15 (2000) 1[4] Annual report, IKP 1997, p. 85 .[5] EEV, England, CCD22 with frame buffer[6] D . Gotta et al., Nucl . Phys . A 660 (1999) 283

2 . Nuclear Spectroscopy

The TMR network project "Development of y-ray tracking detectors"

R.M. Lieder and the TMR Gamma-Tracking Detector Collaboration

The next generation of 47r arrays for high-precision g-ray spectroscopy will consist of -y-ray tracking detectors.They are high-fold segmented Ge detectors and a front-end electronics, based on new digital signal processingtechniques, which allows to extract energy, timing andspatial information for a -y-ray by pulse shape analysisof the Ge detector signals . Utilizing the information onthe positions of the interaction points and the energiesreleased at each point the tracks ofthe -y-rays in a Ge shellcan be reconstructed in three dimensions on the basis ofthe Compton scattering formula .To design ^I-ray tracking detectors for a 4ir -y-detector ar-ray research and technical development is carried out inthe following areas : (i) Development of segmented Gedetectors, (ii) Development of digital signal-processingelectronics, (iii) Development of pulse shape analysismethods, (iv) Development oftracking algorithms and (v)Simulation of tracking arrays .A 47r -y-ray tracking array of large photopeak effi-ciency and resolving power will be composed of multi-segmented Ge detectors . They will allow to determine inthree dimensions the positions at which each -y-ray inter-acts with the array. The interaction points ofthe y-rays inthe Ge detector are localized by means of the segmenta-tion of one or both Ge detector contacts and pulse-shapeanalysis of the segment signals .A six-fold segmented Ge detector has been successfullydeveloped on the basis of the encapsulated Ge detector ofthe EUROBALL project [1] . The Ge detector has a semi-hexagonal shape (hexagonal at the front face and circu-lar at the rear side) and is subdivided into six triangularsegments if viewed from the front face (azimuthal seg-mentation) by separation of the outer implanted contact .This detector is encapsulated, a technology which allowsto cluster them in various configurations and to investi-gate and optimize the cabling, grounding and shieldingto avoid microphony, cross-talk, shifts and oscillations .A 25-fold segmented cylindrical Ge detector which hassix azimuthal and four longitudinal segments plus onecentral circular segment at the front has been devel-oped. It has 25 cold field-effect transistors, one for eachsegment all placed in the Ge crystal vacuum chamber.The energy resolutions of the segments are on average2.2 keV. No cross talk has been observed in the preampli-fier signals .The task of the pulse processing system is to digitize thepreamplifier signal using an analog-to-digital converter(ADC) with sufficient resolution and sampling rate andto provide digital signal processing hardware powerfulenough for on-line processing of the signals . The highdynamic range as well as the bandwidth of the preampli-fiers of around 20 MHz implies the necessity to samplethe preamplifier output signal with at least 12 bit and 40Msps/s in order to allow for the desired digital signal pro-cessing and pulse shape analysis . A -y-ray tracking arrayconsisting of about 100 Ge detectors, which are 20-30fold segmented, will have up to 3000 processing channels

75

producing each a primary data rate of 60 Mbyte/s. Thisrequires a compact digital signal processing electronicswith high computing power for on-line data reduction. Inthe ideal case the whole information should be reducedto only five values per interaction : E.y , t. y and the threecoordinates of the interaction point .A new version of the Pulse-Processing ADC (PPADC)[2] in which up to eight digital processing channels canbe integrated as daughter boards on one mother board hasbeen built in cooperation with the company "target sys-tem electronics GmbH" Solingen, Germany. The motherboard makes the communication with the host PC . Twodaughter board versions exist, a 20 MHz version with a12 bit 20 MHz ADC and two digital signal processors(DSP), and a 80 MHz version with two 12 bit 40 MHzADCs, one programmable logic device (PLD) and oneDSP, whichhas been specifically designed to allow pulse-shape analysis . Software for control, testing, and readoutof the PPADC has been written .Depending on the information which has to be extractedfrom the Ge detector pulses, different optimized signalprocessing algorithms exist or have to be developed andapplied. The time invariant Moving Window Deconvolu-tion (MWD) for instance has been proven to be an opti-mal filter, if information about the released total energyE. y has to be extracted [3] . For timing and pulse shapealgorithms only the leading edge of the signals, i .e . asmall part of the data stream is relevant . For lifetimemeasurements and the extraction of the position informa-tion, a timing with a resolution of sub sampling intervalaccuracy is needed. Therefore a new, digital timing dis-criminator has been designed, the algorithm of which issimple and compact enough to run on-line on the PPADChardware. The concept is based on the idea, that the orig-inal detector signals are steplike in the very beginning .This means, that for a given preamplifier response func-tion a very well defined relation exists between the start-ing point of the signal and the amplitudes of the first fewsamples measured. An algorithm based on this idea hasbeen developed and implemented on the PPADC givinga time resolution of 8 ns for a large-volume Ge detectormeasured in coincidence with a plastic scintillator for a6OCo source taking a large dynamic range.The pulse shapes produced by y-rays interacting witha Ge detector contain the information about the three-dimensional position of each individual interactionwithin the detector volume and the energy released ateach interaction. The tracking efficiency, and hence thefinal performance of a complete tracking array, dependson the precision with which this information can be ex-tracted from the data . The analysis should preferably bedone on-line, to keep the data rate at a level, which can behandled by present data acquisition systems. That is, thealgorithms have to be converted into efficient real-timecode, which has to be implemented on dedicated, highperformance digital signal processing electronics .The charge collection process, i .e. the carrier drift in

Ge crystals at high electric fields and low temperaturehas been experimentally and theoretically studied and ananisotropy of the drift velocity depending on the crystalorientation, as well as an orientation-dependent angularshift of the drift direction have been found [4] . For thefirst time it was demonstrated, that this anisotropic driftof the carriers must be taken into consideration if -y-raytracking is concerned. The experimental investigationshave been carried out with a semi-hexagonal Ge detectorof the EUROBALL project. The detector was scannedwith collimated 22Na and 241Am sources. The measure-ments were taken in the front and coaxial regions of theGe detector . A variation of the charge collection time ofup to 35% is obtained for different drift directions relativeto the crystal orientation . The results are in good agree-ment with simulations and the charge collection processis considered to be well understood now [4] .

Methods for a determination of the interaction positionsof -y-rays in segmented Ge detectors have been devel-oped . They take into account the shapes of the induced"real" and "mirror" charge signals . Real charge signalsare measured at the electrodes of the segment, in whichan interaction takes place . Mirror-charge signals are mea-sured on the electrodes of the neighbouring segments,where no interaction takes place and are due to a capac-itative coupling between these segments and the movingcharges . Simulated signals for real and mirror charges ofa 25-fold segmented detector were used as input to an ar-tificial neural network and a genetic algorithm to studytheir ability to distinguish between single and multipleinteractions and to extract the position and energy infor-mation . A correct identification of the number of interac-tions was obtained for the latter at a success rate of morethan 90% with a position resolution of better than 2 mmand an energy resolution ofbetter than 4% for two events .Furthermore, a pattern recognition system based on thewavelet transform of simulated charge signals was inves-tigated [5] . The coefficients of a "wide-band" (WB4) or-thogonal transformation of the signals were compared todata bases with WB4 coefficients of signal shape types(pattern classes) to identify the best fit via a first nearestneighbour algorithm and a calculation of the membershipfunction ofthe identified class . It was found, that a local-isation of the interaction region in a segment with a po-sition resolution of the order of 1 mm3 may be achievedfor single events, if correlations with mirror charge sig-nals are utilized in the analysis [5] .Extensive simulations of the interaction of y-radiationwith Ge detectors have been performed using the MonteCarlo code GEANT. The simulations have been carriedout for a certain detector geometry and a standard setof -y-ray energies and y-multiplicities . A result which issignificant for the detector development and pulse shapeanalysis is that for a typical Ge detector of 80% relativeefficiency with about 30 segments, the detection ofa 1.33MeV -y-ray produces in 50% of the cases more than oneinteractionpoint in the same segment . Concerning the en-ergy distribution of the individual interactions of a y-rayin a Ge detector it has been found that, rather indepen-dently of the initial -y-ray energy, most of the spectral in-tensity for photoelectric absorption lies somewhat aboveE.y ;z~ 100 keV whereas the Compton scattering spectrum

is peaked at a lower energy.The successful developmentof two alternative algorithmsfor -y-ray tracking has shown that it is a viable solutionfor the development of a new generation of 4.7r y-rayarrays. (i) In one method a two-step procedure is ap-plied. At first clusters of interaction points are identifiedwhich likely represent the path of one -y-ray [6] . Sub-sequently for each cluster, a test of all permutations ofthe coordinates and energy depositions of the interactionpoints against the Compton scattering formula is carriedout in order to distinguish the acceptable sequences fromthose that, because of incomplete absorption of the -y-ray, must be rejected . (ii) The other approach starts frompoints likely to be the last of the interaction sequence be-cause they are associated with an energy deposition inthe range of 100-300 keV and traces the tracks back,step by step using the Compton scattering formula andthe cross sections for photo and Compton effects, to theorigin of the -y-ray without assuming a preliminary clus-terisation . This method is called "backtracking" [7] andallows, in principle, to disentangle the interaction pointsof two -y-rays which enter the detector at a very closedistance . For cascades of 25 y-rays and for an ideal-ized spherical shell geometry, both tracking algorithmsgive presently a reconstruction efficiency of 30 to 70%for Ey = 1 .33 MeV, depending on the assumed accu-racy to which the coordinates of the interaction points canbe determined. The performance of the first tracking al-gorithm depends mainly on the correct identification ofthe clusters while the backtracking is limited by the posi-tion resolution of the interaction points . For backtrackingthe dependence of thereconstruction efficiency and peak-to-total ratio on the resolving distance has been calcu-lated [7] . The general trend is that the peak-to-total ratioand reconstruction efficiency increase with decreasing re-solving distance emphasizing that the position resolutionshould be optimized.It can be concluded, that the basic principles of -y-raytracking have been successfully developed and that a 7-ray tracking array with superior features can be built .Nevertheless, a large amount of detailed technical devel-opment is still required. A proposal based on a Ge shellof 192 -y-ray tracking detectors for experiments with ex-otic beams from the GSI Future Facility is presently inpreperation.This investigation is supported financially by the EU,under the TMR Network Project contract ERBFM-RXCT970123.

References :(11 J . Eberth et al ., NIM A369 (1996) 135[2] W. Gast et al ., to be publ . in IEEE Trans . Nucl . Sci-

(2001)[3] A. Georgiev et al ., IEEE Trans . Nucl . Sci . 41 (1994)

1116[4] L. Mihailescu et al,, NIM A447 (2000) 350[5] L. Mihailescu, Ph.D . Thesis, J"ulich (2000)[6] G.J . Schmid et al ., NIM A430 (1999) 69[7] J. van der Marel and B . Cederwall, NIM 437 (1999)

538

R.M . Lieder, A.A . Pasternak', E.O. Podsviroval , T . Rz4ca-Urban', W. Urban2, M.Re~jmund2, Z. Marcinkowska2,S, Utzelman, H.J . Jensen, W. Gast, H . Jäger, D. Bazzacco3, S . Lunardi3, N.H. Medina , R. Menegazzo3, P. Pavan3,

C.M . Petrache3 , C . Rossi Alvarez 3 , G.de Angelis4 , D.R . Napoli4 , L . Zhu4 , A. Dewalds , S . Kasemanns

The high-spin structure of 144Gd has been studied in Ref.[1] through the 1°$Pd(40Ar, 4n) reaction at E = 182 MeVand as a result irregular dipole as well as stretched E2bands above the 10+ isomer were found. For the interpre-tation of the complex band structure of this semi-magicnucleus the investigation of electromagnetic transition pro-babilities is very important. Here some preliminary resultsof a DSA lifetime measurement for levels with spins up to24 are reported . The reaction mentioned above is onlysuitable for a DSA study of superdeformed bands and veryhigh-spin states due to the large angular momentum (= 60h) of the entry states leading to long cascades and largeside feeding times for the middle sin re ion . Therefore forour DSA study we have used the

spin6S, 6n) reaction at

E = 182 MeV. The y-y coincidence data resulting from aGASP experiment, used before for a DSA study of 145Gdsuperdeformed bands in the 5n channel [2], have beenresorted with a small fold F = (8 -20) and the events havebeen stored in a matrix, corresponding to the summationover all 40 Ge detectors of the GASP spectrometer . Underthese conditions the average angular momentum of theentry states is = 35 h and the calculated effective sidefeeding times do not exceed = 0.3 ps . Since all detectorswere summed the resulting DSA lineshapes are symmetric.Results of a lineshape analysis for the 20+, 21+ states of themost intensive dipole band and the 24+ level of the E2 bandare presented on Fig. 1, 2 .

1,6x10'

1,410'

1,2x10'

m 1,0x10'G

Ü e,Ox10'

6,0x1O'

4,Ox10'

2,0x10'

0.0

1,exle

v,c=O 8,Ox10'U

s,ax10'

4,0x10'

2,Ox10'-I

o,o

Apparatus lineshape

Apparatus iinesnape

Channel number

"'Gd gate 405298keV

Figure 1 : Lineshape analysis ofthe 298 keV (21+ --420)and 504 keV (20+ -> 19~ transitions in the dipoleband of 144Gd. Gates were placed on the 405 keVline . Background lines are marked by * .

DSA lifetime measurements in 144Gd

A similar method of analysis was used in case of the109Ag(13C, p3n)118Te reaction [3] .The work was in part funded by the Russian-GermanCooperation in Science and Technology under the projectnumber RUS-191-99 .1 A.F . Ioffe PTI, RU-194021, St.-Petersburg, Russia2 IEP, Warsaw University, PL-00-681, Warszawa, Poland3 INFN, Sezione di Padova, I-35131, Padova, Italy4 INFN, Laboratori Nazionali di Legnaro, I-35020, Italy5 IKP, Universitilt zu Köln, D-50937, Germany

References :[1] T . Rz4ca-Urban et al ., Nucl . Phys . A579 (1994) 319[2] T. Rz4pa-Urban et ah, Nucl. Phys . A677 (2000) 25[3] A.A . Pasternak et al ., submitted to EPJ A (2001)

4500

4000

3500

3000

,~ 2500C

NCOO

2000

1500

1000

506

01250 1252 1254 1256 1258 1260 1262 1264 1266 1268 1270 1272

Channel number

1250 1252 1254 1256 1258 1260 1262 1264 1266 1268 1270 1272

Channel number1,5

1,4

1,3

1,2

"x 1,1

1,0

0,9

4,40 0,45 0,50 0,55 0,60 0,65 0,70 0,75 0,80

't, PSFigure 2 : Lineshape analysis ofthe 889 keV (24+ --> 22~

transitions in the stretched E2 band of 144Gd. Gateson the stopped component ofthe 1018 keV line(12+--> 10~ and a wide gate of38 keV width onthe stopped and flight components of the 755 keVline (20+ -> 18~ were used .

1,6x10' 144Gd gate 4051,4x10' 504keV1,2xlO'

s(20* ) =1.2(0.4) ps1,0x10'

Isomeric states with I"=8- and K=8 have been knownin all even-even N=74 isotones with atomic number Z =54 - 64 [ 1] . The respective isomeric half-lives vary by sixorders of magnitude, from nanoseconds (Xe) to millisec-onds (Ce, Ba). Their modes of decay are also different,but decay branches of El transitions with a degree of K-forbiddeness v of 7, leading directly to the 8+ member ofthe ground state band (gsb) with K=0have, been found in130Ba,134Nd,136Sm and 138Gd. These branches severelyviolate the K selection rule. The respective El transitionrates differ by four orders of magnitude . The reducedhindrance factor, i .e . hindrance factor per degree of Kforbiddeness, f v, is about 6 for 134Nd,134SM and 138Gdand increases significantly to a value of 12 for the 13'Baisotope.

The investigation of the nucleus 132Ce, which liesjust inthe region of a significant change of the hindrance fac-tor for the El transition, has been undertaken with theaim to look for such an El decay branch and, conse-quently, to achieve a better understanding of the deexcita-tion mechanism of the K''=8- isomers in the N=74 iso-tones. Levels in the 132Ce nuclei have been populated inthe 120Sn(1o0,4n) reaction at a beam energy of 80 MeVThe 1°0 beam was provided by the U200P cyclotronat the Heavy Ion Laboratory of the Warsaw University.The target was a self-supporting metallic foil (6 mg/cmzthick) consisting of isotopically enriched 1z0Sn . The de-layed y-radiation was studied with the OSIRIS multide-tector array which consisted of 6 Compton-suppressedHPGe detectors utilizing the macro structure of the beam .The macro pulses had a length of 1 .5 ms with a time sep-aration of 8.5 ms .

T. Morek', J. Srebrny', Ch . Droste', M. Kowalczyk', T. Rz~ca-Urban', K.Starostal, W. Urban', R. Kaczarowskiz,E . Ruchowskaz, M. Kisieli6ski3 , A. Kordyasz 3 , J . Kownacki 3 , M. Palacz3 , E. Wesolowski3 , W. Gast, R.M . Lieder,

P Bednarczyk4 , W. Mgczy6ski4 , J . Styczen4

+=

14 434+

2377

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..R: .. . . . . . . . i

8

Figure 1 : Decay scheme ofthe K 11 = 8- isomer in the nu-cleus 13zCe as established in the present study.The transition energies are given in keV Thewidths of the arrows are proportional to the rel-ative intensities ofthe observed 't-transitions.

Investigation of the Yff = 8- Isomer in 13zCe

78

The decay scheme of the 8- isomerdetermined in this ex-periment is presented in Fig . 1 . An excitation energy of2340.2 f 0.5 keV and a half-life of 9.4f0.3 ms has beenobtained for the 8 - isomer in this experiment . In additionto the already known isomer decay to the 6+ level via the798.0 keV transition, two new isomeric decay paths wereestablished. A weak 788.Of0.2 keV transition was iden-tified with the 8+ -3 6+ gsb transition already knownfrom previous studies . The presence of this transition inthe off-beam y - y coincidence spectra proves the exis-tence of an unobserved 10.00.5 keV E1 transition con-necting the 8- isomer with the 8+ gsb level at 2330 keV,and establishes a new decay path of the isomer. A sec-ond previously unknown decay proceeds via a 526 keVtransition to a new level at 1814 keV as deduced fromcoincidence relations . This newly established level de-excites via the 614, 431 and 955 keV transitions to the3,+y and 4,+Y levels of the -y-band and to the 4+ gsb level,respectively.Information on the decay properties of the 8- isomer canbe obtained from hindrance factors F deduced for the de-exciting transitiöns by a comparison of the partial half-lifes ofthey-transitions and the corresponding Weisskopfsingle particle estimates . A convenient way to comparethe retardation of K-forbidden transitions of multipoleorder L in a quantitative manner is through reduced hin-drance factors fv, defined as fv=F'w, where v is the de-gree of K-forbiddeness defined as v = OK - L. In caseof E1 transitions, the Weisskopf estimate is usually mul-tiplied by a factor of 104 to take into account the generallystronger El hindrance with respect to the Weisskopf es-timate and thus to facilitate a comparison with transitionsof other multipolarities .The 8- isomer in 13zCe decays via highly K-forbidden,y-transitions to the members ofthe ground state band andquasi rotational -y-band . The values deduced for the re-duced hindrance factors f1 = 9.0(0.5) and ß= 6.7(0.1),for E1 and E3 transitions, respectively, fit into the sys-tematics of the hindrance factors for the even-even N=74isotones . A simple two-band mixing model involving aninteraction ofthe gsb and the s-band [2] allows for an ex-planation of the observed Z dependence of the reducedhindrance factors f1 for E1 transitions . In the case ofthe E3 transitions it is shown that a nonaxial deformationshould be taken into account. The observed similar val-ues of fs for 13oga and 13zCe may be related to a nearlyconstant y-deformation deduced for these nuclei .' lEP, University of Warsaw, Warszawa, Polandz SIN, Swierk, Poland3 HIL, University ofWarsaw, Warszawa, Poland4 NINP, Kraköw, Poland

References :[1] R.B . Firestone, Table of Isotopes, 8th Edition, 1996[2] A.M. Bruce et al ., Phys.Rev. C 55, 620 (1997)

8+ 2330 .» . .j" 8_0 ' . . . . . 2340-~ 9.4 ms

1788 798 52611

101

6+

683 955 / . . . . . . . . .

524 34Ö

_ . ..1-------

54+

7- 874

One of the most difficult problems of the DSA method is ashow to take into account the delay time feeding distributionconnected with cascades of quasi-continuum spectra fromthe entry state region into the investigated levels (sidefeeding) . For small excitation energies and angularmomenta, induced by relatively light bombarding particlesnear the Coulomb barrier, the effective side feeding time(,r,f) is usually short compared to the lifetimes of levels (rt)

and the stopping time of the recoils (tisf = 0.1 ps << r) andcan be taken into account semi-empirically [1, 2] . For heavyion induced reactions used in high spin spectroscopytypically ti5f > 0.2 ps and the DSA lifetime analysis stronglydepends on the model for the side feeding pattern [3] . Ratheroften for nuclei which lie in the region of good rotors theside feeding branch of the level population is described byone effective rotational band with one additional parameter- the quadruple moment Q. More complex calculationstaking into account (usually by Monte-Carlo methods) allpossible side feeding cascades starting from the entry statesregion are generally based on the assumption that sidefeeding is mainly defined by the competition betweenstretched E2 bands and statistical transitions [4] . More recentcalculations of the quasi-continuum y-flow are taking intoaccount a number of additional effects [5], in particularrotational damping, connected with band mixing, but theyare not applied to the delay time feeding distribution .Now we are trying to improve the side feeding patterncalculations for DSAM application and to extend them to thecase of nuclei lying close to semi-magic N = 82 nuclei, inparticular to 144,142Gd. For this purpose the codes for preciselineshape analysis COMPA, GAMMA, SHAPE (Ref. [l, 2]for instance) have been complemented by the codeCARLIC, This Monte-Carlo code takes = 500000 entry stateevents, simulated by the code COMPA taking into accountthe formation and decay of compound nuclei, and simulatesthe time-distribution of the side feeding cascades betweenthe entry states and the considered yrast level . To check thevalidity of the model hypotheses and parameters there is thepossibility to calculate additional distributions, such as formultiplicity, relative cascade and side feeding population,

40

W

Spin

Figure 1 : Entry state distribution of 144Gd, calculated bythe Monte-Carlo code COMPA. The dashedline represents known yrast states and after spinI = 30 ti the superdeformed yrast band. The solidline is the parabolic extrapolation of yrast levelsinto the high spin region (I < 30 ti).

Side feeding pattern calculation near N = 82 nuclei

A.A. Pasternak', R.M . Lieder, W. Gast, E.O. Podsvirova l

79

multipole spectra etc. In addition to the well-knownrotational damping effect the possibility of Ml transitionsbetween mixed bands have been included in thecalculation. For the case of near-magic nuclei two specialhypotheses have been made viz. to consider the influenceof superdeformed bands (Fig. 1) and the existence of alarge amount of particle-hole excitations in the entry stateregion and magnetic rotational bands with shears effects[6] .The last hypothesis can be checked by a comparison of ourcalculations (Fig. 2) with experimental data shown in thefigs. 2 of Refs . [7, 8] on linear polarization. A reasonableagreement between multipole spectra, quadrupoleldipolefraction relations and multiplicity has been achieved .The work was in part funded by the Russian-GermanCooperation in Science and Technology under the projectnumber RUS-191-99.1 A.F. Ioffe PTI, RU-194021, St.-Petersburg, RussiaReferences :[1] A.A. Pasternak et al ., EPJ A09 (2000) 293[2] J . Srebrny et al., Nucl. Phys . A677 (2000)[3] P. Petkov et al ., Nucl. Phys. A640 (1998) 293[4] F.Cristancho et al ., Nucl . Phys . A501 (1989) 118[5] T . Dossing, E. Vigezzi, Nucl . Phys . A587 (1995) 13[6] A.O. Macchiavelli et al ., Phys . Lett . B450'(1999) 1[7] H.Hiibel et al ., Z.Ph . A297 (1980) 237[8] M. Deleplanque et al., Phys . Rev. Lett . 41(1978)1105

100

1000 -_

" E2(AI" 2) .E1,Ml(Al .0)frecban-57.3% mullolle ly-f 7.7-

11°Pd+ eAr--> ts'Gd E=170 MOVAll reaction channels are taken Into account

+ m.0Wkrouoonle .«Itch .d on-4 .e%

6o0

t000

fs0 0 '

'- '2000

E, (W)2500

Figure 2 : Multipole spectra calculations for comparisonwith experimental spectra of linear polariza-tion investigations [7, 8] . Statistical Ml andE2 transitions are not taken into account butMl transitions between mixed bands areincluded in the calculation .

0 M1(AI " 1)1-11-33.7% -I11pli . ty.0 .1

m El(A1 .1)Iraclkn.u.0% mulllpllelly.2 .4 J

ö10000 ,

"

N+ + middle total m6mpnoly.xs .4

C

1-

1000- + " . . . .me0nelk7olalbn ~ eIt .WItched off-5 .7% .

'0 500 1000 1500 '20000' 2500

E , (keV)

12'Sn +°Ar-- >"'Er E=170MGVAll reaction channels are taken into account

100000-- " -" " frne0on .7p.6% mulllplk0y.1p.0

" " " M1(AL1)at1-9-10 .6% M.UIP11.1"3 .2

" ~ E1(AL1)

fr.alkn.9.7% multiplicity-2A>

at middle total MUMPliclly-23.0

0 10000 " -0

R

c

1 . Introduction

The main task of the on-line digital pulse shape anal-ysis for -y-ray tracking is to reduce the huge primarydata rate of the continuously sampled preamplifieroutput signal (40 Msps/s * 12bit = 60 MByte/s),which for a 36-fold segmented detector amounts toa total data rate of 2.16 GByte/s per detector, to areasonable level, and to provide a compact represen-tation of the interesting information to be extractedfrom the signal . In the case of a tracking detec-tor these are the: the number of -y-ray interactionswithin the detector volume, their time of occurence,the amount of energy deposited at each interaction,and the exact 3-D positions of the interactions.The energy information is extracted from the totalintegral over the detector current. A time invari-ant filtering allowing a true ballistic measurementand adaptive shaping has to be employed, if oneaims at optimal resolution and high throughput si-multaneously. The Moving Window Deconvolution(MWD) algorithm [1], being the only one known upto now to provide these features, is the classical pro-totype of an on-line pulse shape analysis algorithm,since it analyzes the full data stream of the sampledpreamplifier signal on its input (60 MByte/s) andreduces it to one energy value per event on its out-put (typ . 20 Kevents/s * 14bit = 35 KByte/s) . Thepulse shape analysis to extract the time and positioninformation on the other hand can be restricted toa small region around the leading edges of the de-tector signals at the output of the preamplifier, i.e .the required processing power mainly scales with theevent rate . The digital algorithms to achieve a three-dimensional position sensitivity are described in aseperate contribution to this report . In this contri-bution the digital pulse shape analysis methods toextract trigger and timing information are presented .

2 . Triggering

On-line Digital Pulse Shape Analysis for Gamma-ray Tracking

Since all of the digital pulse shape analysis algo-rithms for ^I-ray tracking discussed so far need tobe informed about the beginning or presence of adetector signal, the generation of a trigger signal isone of the first signal processing tasks. Although awide variety of conventional, analog discriminatorsexist, this task should preferably be solved by digitalmeans, too, in order not to add unnecessary com-plexity to the signal processing system . The digitaltrigger/discriminator algorithm should be optimizedfor good signal-to-noise (SIN) ratio and reasonabletime resolution. Good SIN ratio means low thresh-old triggering . This is essential considering, that notonly source y-rays but also scattered ones might havesmall energies, but nevertheless should be detectednot to spoil the reconstruction ofthe full energy peak

W. Gast, M. Rossewij, L. Mihailescu, R.M. Lieder

80

via add-back . Reasonable time resolution is desir-able, if one wants to use the signal for on-line coin-cidence timing, too.A new digital trigger algorithm has been developed,which uses an unconventional filter approach to pro-vide optimal SIN ratio and reasonable timing accu-racy. In a moving time window of the size of therisetime of the preamplifier output signal all -condi-tions characterizing the presence of a leading edgeslope of a pulse, are checked. The averaged sum ofthe actual number of fullfilled conditions representthe output signal of this time invariant filter . Its re-sponse function reaches maxima, when the movingwindow actually covers the leading edge of a pulse .The time of occurence of these maxima, detected bya maximum detector and compared to a predefinedthreshold, represents the output of the new triggerdiscriminator. Due to this architecture the discrimi-nator is to far extend insensitive to variations of theactual noise level, of the amplitude and the detailedshape of the pulses . It is virtually parameter free,since the adjustment of the only two parameters,window size and threshold, can easily be done auto-matically. Refering to its operation principle the newtrigger algorithm is called Slope Condition Counting(SCC) discriminator .The algorithm has been implemented on the PLD ofthe fast PPADC [2], and an output signal, which issynchronized to the 40 MHz system clock, is providedto test the performance. The low energy efficiency,i.e . the low threshold performance, has been exper-imentally measured using a large volume HPGe de-tector of 32% relative efficiency irradiated by a com-bination of a 60Co and a'41Am source . The win-dow size of the filter was adjusted to 250 ns, i.e . 10sampling intervals. In fig. 1 the resulting efficiencycurve (solid line) is compared to those of an ana-log Constant Fraction Discriminator (CFD Canberramodel 1326A), with two different parameter settingsoptimized for low threshold (dotted line) and goodtiming (dashed line), respectively. The observed ef-ficiency is 80% at 10 keV and 100% down to 20keV.The timing performance was measured over the fulldynamic range from zero to two MeV using the samedetector irradiated by a 60 Co and 22Na source . TheCFD optimized for good timing and alternatively afast scintillor with leading edge discriminator wereused as time reference. The new trigger algorithmdetected 99% of the events within a time range of195 ns and 90% within a range of 103 ns . The lattercorresponds to approx . 4 sampling intervals, whichis a satisfactory result considering the simplicity ofthe algorithm and the fact, that the risetimes of thesignals varied between 6 and more than 14 samplingintervals . For our system the accuracy is sufficient tocontrol most of the subsequent processing tasks. Inmany cases the Full Width Half Maximum (FWHM)

v 2

GvvWv

rovmrn

rou

äNrovL

0

Figure 1: Measured efficiency of the SCC discrim-inator (solid line) compared to that ofan analog Constant Fraction Discriminator (CFD Canberra model 1326A) for twodifferent parameter settings optimized forlow threshold (dotted line) and good tim-ing (dashed line), respectively.

of 50 ns, which approaches the theoretical minimumof two sampling intervals, may also satisfy the re-quirements for coincidence timing .

'

3. Timing

0

50

Energy [keV3

100

For precise lifetime measurements and on-line pre-processing tasks, like the wavelet transformation toprecondition the signals for the extraction of the po-sition information, a timing with a resolution of subsampling interval accuracy is needed. Therefore anew, digital timing discriminator has been designed,the algorithm of which is simple andcompact enoughto run on-line on the PPADC hardware . Theconceptis based on the fact, that the original detector signalsare steplike in the beginning, the step shape being af-fected by variations of the charge collection processonly after approx . 50 nanoseconds. This means, for anormalized step amplitude exists a very well definedrelation between the starting point of the signal andthe amplitudes of the first few samples measured .This relation is modified, but still well defined afterthe detector signal is shaped by the preamplifier re-sponse function, which is constant . Refering to itsoperation principle we call the new, digital timingalgorithm Normalized Step Response (NSR) tim-ing discriminator. In table 1 the measured perfor-mance of the NSR discriminator with respect to timeresolution and efficiency is compared to a conven-tional digital approach, the Extrapolated BaselineCrossing with linear (EBC1) and quadratic extrap-olation (EBC2), respectively. The time spectra weremeasured for a 60Co source using the leading edgediscriminated signal of a fast lead glass scintillatoras timing reference. Although no optimazition of theparameters (antialiasing filter, shape correction, etc.)

81

Table 1 : Performance of the NSR timing discrimina-tor (see text).

N1J

UU

250 300 350 400

channel number

Figure 2: Experimentally measured sub sampling in-terval timing accuracy of the digital NSRdiscriminator running at 40 Msps/s sam-pling speed.

has been done so far, the results compare well withthose obtainable from conventional state-of-the-artdiscriminators . In fig . 2 the time spectrum of theNSR discriminator, obtained for the full dynamicrange of 0 MeV to 2 MeV and 25 ns sampling in-

terval, is shown as an example.

This work is supported by the EU in the frameworkof the TMR program under the contract ERB FMRXCT 970123 .

References :

[1] A. Georgiev and W. Gast, IEEE Trans. Nucl .Sci., Vol. 40, No. 4, (1993) 770

[2] M. Rossewij et al ., IKP Annual Report, Jülich(1999) 83

Full dynamic range Dyn. range 1.0-1 .4 MeVAlgorithm FWHM Efficiency FWHM Efficiency

[ns] [%] [ns] [%]NSR 8.5 68.5 6.5 80.2EBC2 9.0 63.4 7.0 79.9EBC1 14.0 63.1 11.5 76.8

Digital Algorithm for Three-Dimensional Position Sensitivity with High Resolution Ge Detectors

The development of y-ray tracking systems requires newlarge volume, segmented 7-ray detectors accompaniedby new signal processing algorithms and systems able toidentify they-ray interactions with high energy and posi-tion resolution . "y-ray tracking" is a concept introducedto increase the performance of high resolution spectro-scopic methods used in nuclear physics . By using thisconcept, a reconstruction of the incident -1-ray events willbe possible by determining their scattering sequence uti-lizing the Compton scattering formula .The most important aim of a detection system to be use-ful for -y-ray tracking is to provide the energies and posi-tions of multiple interactions in full 3D coordinates . Forthis purpose, digital pulse shape analysis methods weredeveloped . Figure 1 shows a simplified flow diagramof the digital algorithm which, using as input variablesthe "wide-band" wavelet transform coefficients of the de-tector segments pulse shapes, identifies the multiple -y-ray interactions in three-dimensional coordinates [1] . Inthe following, the signals of the segments in which en-ergy was deposited are named "real" signals, whereas thesignals induced in the neighbouring segments to the ir-radiated one are named "mirror" signals . Similarly tothe simpler 21) case, firstly, the segments with depositedenergies are identified . For each such segment, a num-ber of "real" pattern classes C""

t are extracted from adata-base for the unknown signal pattern X . Utilizingthe knowledge on the classes Cent, the correspondingradii of interaction can be deduced . Having determinedthe number of "real" signal components, the segments inwhich "mirror" signals are expected can be identified .For each such segment with "mirror" signals, a set ofvalues M(s', j) = {s, i, Ci} are memorized containingfor each "mirror" signal of index j in the segment s',the corresponding "real" component identified as Ci inthe segment s . For each of these segments with "mir-ror" signals, having known the corresponding "real" sig-nals, the induced amplitudes due to various interactionsare decomposed . The amplitudes Aj are found by min-

zimizing :

(X- Z~ °i Aj C,;} . The ratio between the

amplitudes Aj of the "mirror" signals corresponding toa "real" component C%, will give, the measure which de-termines the position of the interaction relative to the twoneighbouring segments . In this way, the other two cylin-drical coordinates are deduced, the interaction positionsthus being fully characterized .An example is presented in fig . 2 . A particular combi-nation of four interactions were simulated and identifiedwithin 2mm. The complexity limit imposed in this exam-ple involves a maximum number of one "real" and three"mirror" signal components per segment. For segmentsbeing exposed to more components, the positioning reso-lution decreases, especially in the azimuthal and longitu-dinal coordinates .Work supported by the EU under the TMR Network con-tract ERBFMRXCT970123

L . Mihailescu, W Gast, R.M . Lieder

82

-

The wavelet coefficientsI

s =1

of the segments (Xs)

1

Estimate the amplitude Aiof the class Ci in the Xs ;

Xs =Xs - Ai'Ci :

s'= 1

Read M s',j)={s,i,CI), j=1 :Js ;

Existsmirror ?

no yes

The positions Prhand energies E(i)

i ._ .,---,-_,-of the interactions

yes

no

loo

yes

-----------------

Data base withthe features ofpattern classes(waveletcoeff.

no ye'

Compute distances from Xs to real

i- i+1

pattern classes; Take best class Ci ;

etermine the segments s' with 'mirrorsof type Ci; Memorize M(s',j)={s,i,C1);

Incre ment I for each s';i~-

isthe distancedi > delta?

/___S-_1 ?\1

Decompose 'mirrors' M(s',j), j=1 :Js;Determine the amplitude of the'Mirror' comp. of Ci: A(s',s;i);

For each interaction i, calculate ratiosA(s',s,i)/A(s",s,i) ; s',s" are neighbour

s_s+1segments ; Determine positions P(i);

Figure 1 : Simplified flow diagram of the algorithm .

0

Figure 2 : Example of identified multiple interactions .

References :[1] L. Mihailescu, PhD Thesis, Bonn (Nov. 2000) ;

11 .

Theoretical Nuclear Physics

3. MEDIUM AND HIGH ENERGY PHYSICS

4. NUCLEAR STRUCTURE ANDREACTION MECHANISM

3 . MEDIUM AND HIGH ENGERGY PHYSICS

The pion charge radius from

V. Bernard (Strasbourg), N.

The charge (vector) radius of the pion is a funda-mental quantity in hadron physics. It can essentiallybe determined in two ways. One method is pion scat-tering off electrons (or electron-positron annihilationinto pion pairs), this leads a pion root-mean-square(rms) radius of (r,2)v 2 = (0.663 ± 0.006) fm . Thesecond method is based on charged pion electropro-duction, -y*p --+ 7r+ n. Here, y*, p,n and 7r+ denotethe virtual photon, the proton, the neutron and thepositively charged pion, in order. The unpolarizedcross section in parallel kinematics decomposes intoa transversal and a longitudinal piece. While the for-mer is sensitive to the the nucleon axial radius, thelatter is quite sensitive to the pion form factor, i.e . tothe pion radius for small momentum transfer . A re-cent measurement at the Mainz Microtron MAMI-IIled to a pion radius of (r7)Ü

2 = (0.74±0.03) fm [1],which is a sizeably larger value than the one ob-tained from gyre scattering . It was hinted in Ref-[1]that their larger value for the pion radius might bedue to the inevitable model-dependence based on theBorn term approach to extract the pion radius . Itwas also stated that there might be an additionalcorrection obtainable form chiral perturbation the-ory as it is the case for the nucleon axial radius . Sucha correction based on pion loop diagrams had beenpredicted in 1992 for the axial radius[2] andwas veri-fied by the MAMI experiment to agood precision. Inref.[3] we show that there is indeed a similar kind ofcorrection for the pion radius . This new term mod-ifies the momentum dependence of the longitudinalS-wave amplitude Lö+) and leads one to expect aneven larger pion charge radius than the one givenby the MAMI analysis . It is conceivable that higherorder corrections yet to be calculated or contribu-tions from higher multipoles will completely resolvethe discrepancy between the pion radius determinedfrom Ire scattering on one side and from charged pionelectroproduction on the other.Chiral perturbation theory allows one to makemodel-independent statements based solely on thespontaneously and explicitly broken chiral symme-try of QCD. S-matrix elements and transition cur-rents are expanded in powers of small external mo-menta and quark masses . Of particular interest arethe so-called low-energy theorems, which give pre-dictions to a certain order expressed entirely in termsof measurable quantities . Our starting point is thelow-energy theorem for the longitudinal dipole am-plitude Lö+), accessible in charged pion electropro-duction . It has been derived from baryon chiral per-turbation theory to third order in the chiral expan-sion [4] . This leading order result will not be affectedby a more systematic expansion in the inverse of thebaryon mass or using some other type of regulariza-tion . To separate the pion radius, one should consider

Kaiser (München), Ulf-G. Meißner

87

charged pion electroproduction

the slope of the longitudinal multipole . This gives:

(9Lö+)

_ eg"N _1

1

13äk2 ik2=0

32am {M77r

MM, + Sm2

+3(r')v + 32F,2, (7r6 - 1) + 0(M") } .

(1)

The first four terms are standard . The last term orig-inates from the so-called triangle and tadpole dia-grams. The formal reason for the appearance of thisnew, model-independent contribution at order k2 isthat one cannot interchange the order of taking thederivative at k2 = 0 and the chiral limit M" --+ 0.Consequently, all determinations of the pion radiusfrom electroproduction (based on tree-level ampli-tudes including nucleon and pion form factors) have"measured" the modified radius,

(-7_2

2)V 3 (1632F 7r

(,)V = (0.44+0.26) fm2 = (0 .83 fm) 2 ,

References :

The novel term on the right-hand-side of Eq.(2)amounts to 0 .266 fm2, a bit more than half of thesquared pion rms radius, (rn)V 0 .44fm2. There-fore, from the longitudinal multipole alone, one ex-pects to find a larger pion radius if one analyses pionelectroproduction based on Born terms,

which is even larger than the result of the Mainzanalysis . We point out, however, that the contribu-tion of the pion radius to the derivative of the longi-tudinal multipole is a factor of ten smaller than theone from the first three terms in the curly brackets inEq.(1) . Therefore, a fourth order analysis is certainlyneeded to further quantify the "pion radius discrep-ancy" . One should also investigate such effects forthe higher multipoles or directly compare the pre-dictions of complete one-loop calculation with thedata of the longitudinal electroproduction cross sec-tion . What we have shown is that as in the case ofthe nucleon axial mean square radius, the pion loops,which are a unique consequence of the chiral symme-try of QCD, modify the naive Born term analysis andshould be taken into account .

[1] A. Liesenfeld et al ., Phys . Lett . B468 (1999) 20 .

[2] V. Bernard, N. Kaiser and Ulf-G . Meißner,Phys . Rev. Lett . 69 (1992) 1877 .

[3] V. Bernard, N. Kaiser and Ulf-G . Meißner,Phys . Rev. C62 (2000) 028201 .

[4] V. Bernard, N. Kaiser, T.-S.H . Lee and Ulf-G. Meißner, Phys . Reports 246 (1994) 315.

Neutral pion electroproduction off deuterium above threshold

Chiral perturbation theory has been successfully ap-plied to neutral pion photo- and electroproductionoff the proton as well as to -7r° photoproduction on thedeuteron [1] . The scattering off deuterium is not onlyinteresting per se, but also because this loosely boundtwo-nucleon system can be used as a neutron target .In particular, in ref.[1] it was shown that one can in-deed extract the elementary 7r°n production ampli-tude from a precise measurement on the deuteron .Furthermore, at MAMI experiments for neutral pionelectroproduction off deuterium at small photon vir-tualities have been untertaken and are presently be-ing analyzed [2] . A first results for this process ex-actly at threshold to third order in chiral perturba-tion theory was obtained in [3] . The resulting elec-tric S-wave amplitude Ed is in rough agreement withthe preliminary analysis of the MAMI data whereasthe longitudinal S-wave mulitpole Ld is much smallerthan predicted, leading in particular to a sizeableoverestimation of the S-wave cross section. However,the data have not been taken directly at thresholdand thus a calculation above threshold is manda-tory for a more direct comparison . For doing that,we first have generalized the well-known CGLN for-malism for pion production off nucleons to the spin-1 case (the helicity formalism developed in ref.[4] isless appropriate for studying the threshold region),i.e . the neutral pion electroproduction amplitude offthe deuteron is written in terms of 9 transverse and 4longitudinal operators and corresponding transition(CGLN) amplitudes,

13

Md(w1 k2)

=

E Os ,17i (w, k2)i=1

where the Ci are expressed in terms of the pion andphoton momenta, the photon polarization vector andthe spin operator of the deuteron . The transition(CGLN) amplitudes .Pi depend on the pion energy wand the photon virtuality k2 . The explicit mappingon the multipoles Xi~ with L the total orbital an-gular momentum, L,r the pion angular momentumand J the total angular momentum can be found in[5] (as usual X stands for electric E, longitudinal Land magnetic M transitions) . The matrix-elementitself decomposes into the single scattering (ss) andthe so-called three-body (tb) contribution . So far, wehave calculated the three-body contributions to thetwo S- and the six P-waves to third order for virtu-alities up to k 2 = -0 .1 GeV2 and invariant energiesabove threshold AW --_ 0 . . . 15 MeV. E.g ., for the P-waves, one has to consider eight topologically differ-ent Feynman diagrams . The O(q3) results for the twoS-waves Eöl and Löl as well as the dominant mag-netic P-waves M11,12 are shown in fig.1 as a functionof AW for k2 _ -6 .1GeV2 . The S-wave multipolesclearly exhibit the unitary cusp due to charged to

V . Bernard (Strasbourg), H. Krebs, Ulf-G . Meißner

88

neutral pion mass difference (since the two nucleonsin the initial and the final state are bound, this massdifference appearing in tree graphs suffices to gen-erate a cusp . This is different in pion production offfree nucleons) . The electric and longitudinal P-wavesare sizeably smaller than the magnetic ones shown infig.l . We are presently working out the single scat-

-0.05

References :

[3]

[4][5]

-0.1

-02502468101214

-0 .30

2

4

6

8

10

12

14ew [nlev]nw WWI

Figure 1 : S-wave and P-wave multipoles of thedeuteron (3-body contribution) . In the upper panel,the electric dipole E011 and the longitudinal (L 11)multipoles are shown, respectively, by the solid lines .In the lower panel, we exhibit the dominant magneticmulipoles Mil and Mit.

tering P-wave contribution . When that is finished, abetter comparison with the MAMI data will be pos-sible and it remains to be seen whether the presentdiscrepancies persist and whether they already orig-inate from the single scattering contribution (whichis probable in the light of the recent pr o electropro-duction results off' the proton at k2 = -0.05 GeV2,see ref.[2]) .

S .R . Beane, V. Bernard, T.-S .H . Lee, Ulf-G. Meißner and U. van Kolck, Nucl . Phys . A618(1997) 381.H. Merkel, plenary talk at Chiral Dynamics2000 : Theory and Experiment, Newport News,July 2000 .V. Bernard, H . Krebs andUlf-G . Meißner, Phys .Rev. C61 (2000) 058201 .H . Arenhoevel, Few-Body Syst . 27 (1999) 141 .V . Bernard, H. Krebs and Ulf-G . Meißner, inpreparation.

Complete one-loop analysis of the nucleon's spin polarizabilities

Low energy Compton scattering off the nucleon isan important probe to unravel the nonperturbativestructure of QCD since the electromagnetic interac-tions in the initial and final state are well understood .Quite recently, with the advent of polarized targetsand new sources with a high flux of polarized pho-tons, the case of polarized Compton scattering off theproton yjp"--+ yp has come close to experimental fea-sibility . On the theoretical side it has been shown [1]that one can define 4 spin-dependent electromagneticresponse functions -1i, i = 1 . . . 4, which in analogy toelectromagnetic polarizabilities ix , ß are commonlycalled the "spin-polarizabilites" of the proton . In [2]we have taken up the challenge on the theory sidewithin the context of Heavy Baryon Chiral Pertur-bation Theory (HBCHPT) and presented a full one-loop, C(p4), analysis . The pertinent results of thisinvestigation are :1. At 0(p4) one has to resort to a definition of the(spin-) polarizabilities that is soundly based on fieldtheory, we therefore advocate the following defini-tion for the spin-dependent polarizabilities in (chi-ral) effective field theories : Given a complete set ofspin-structure amplitudes for Compton scattering toa certain order in perturbation theory, one first re-moves all one-particle (i .e . one-nucleon or one-pion)reducible (1PR) contributions from the full spin-structure amplitudes . To be more precise, at order0(p4) one removes F(w)/w terms from the ampli-tude, where F(w) denotes the energy dependence ofthe yNN vertex function .2 . Utilizing this definition, we have calculated thefirst subleading correction, (ß(p 4), to the 4 isoscalarspin-polarizabilities y(s) already determined to 0(p3)in [3] in SU(2) HBCHPT. The resulting expressionscan be given in closed analytical form and are free ofundetermined parameters. The results are collectedin the table (in the units of 10-4 fm4) .

With the notable exception of y4s), which evenchanges its sign due to a large C(p4) correction,we show that this first subleading order of y(s)13amounts to a 25-45% correction to the leading or-der result . This does not quite correspond to theexpected M,r/mN correction of (naive) dimensionalanalysis, but can be considered acceptable . The largecorrection in -14s~ should be considered accidental . Itis not related to any large A effects, because thesewill only show up at 0(p5) in the HBCHPT frame-work.

G . Gellas, T.R . Hemmert, Ulf-G . Meißner

89

3. We further report the first results for the 4isovector spin-polarizabilities yi~") obtained in theframework of chiral effective field theories . Previ-ous calculations at third order were only sensitiveto the isoscalar spin-polarizabilities . Again, we haveparameter-free predictions:

with'Y4")

References:

e29Ä f 57r96 7r3F72

LO -urM72 g]

'

e29r

(1

+

h(s))~11927r3F2M2

0 -

4e29A 71

3847r3F~ M~ LO + p 4

'0,

p. = Mr/MN. The resulting numerical valuesare yiv) = -1 .3, -I(V) = -0.2 and yäv) = 0 .1 (incanonical units) . The result of our investigation isthat the size of the 7i") really tends to be an orderof magnitude smaller than the one of they~s) (withthe possible exception of y("), supporting the scal-ing expectation, yc") N (Mn/mN)y~s) from .(naive) .dimensional analysis . This is reminiscent of the sit-uation in the spin-independent electromagnetic po-larizabilities ä("), P("), which are also suppressed byone chiral power relative to their isoscalar partners

, ß(s) .4. We have also commented on the comparison be-tween our results and existing calculations using dis-persion analyses . In an effective field theory approachincluding also the delta resonance, it was alreadyshown [4] that 2 ('Y2, y4) of the 4 spin-polarizabilitiesreceive large corrections due to 0(1232) related ef-fects, resulting in a big correction to the leading1/M,2 behavior . Therefore, we do not consider our0(p4) HBCHPT result for y23~,y4') to be meaning-ful. Their large inherent 0(1232) related contribu-tion just cannot be included (via a counterterm) be-fore 0(p5) in HBCHPT that only deals with pionand nucleon degrees of freedom. The correspondingisovector combinations, however, again seem to agreequite well with the dispersive results and so far wehave no reason to suspect that they might be af-fected by the poor convergence behavior of some oftheir isoscalar counterparts .

[1] S. Ragusa, Phys . Rev . D47 (1993) 3757 .[2]

G.C. Gellas,T.R . Hemmert andUlf-G . Meißner,Phys . Rev . Lett . 85 (2000) 14 .

[3] V. Bernard, N. Kaiser and Ulf-G. Meißner, Int.J. Mod. Phys . E4 (1995) 193.

[4] T.R . Hemmert, B.R . Holstein, J. Kambor andG. Kn6chlein, Phys . Rev. D57 (1998) 5746 .

0(p3) 0(p4) Sum

yls) +4.6 -2.1 +2.5yäs~ +2 .3 -0.6 +1.7yis) +1.1 -0.5 +0.6y49) -1.1 +1 .5 +0.4

Hadrons are composite objects, characterized by cer-tain probe-dependent sizes . Their structure can beinvestigated by use of electron scattering (or the in-verse process) . The electromagnetic structure of theproton and the neutron has been investigated overdecades. In the non-perturbative low-energy regionof QCD, baryon chiral perturbation theory can beused to calculate these form factors . In a recent pa-per [1] we have shown that relativistic baryon chi-ral perturbation theory (employing the so-called in-frared regularization of [2]) supplemented by explicitvector meson contributions allows for a fairly pre-cise description of these fundamental quantities forphoton virtualities up to QZ - 0.4 GeV2. The exten-sion of these considerations to the three-flavor caseis interesting for various reasons. First, the chargeradius of the E- has recently been measured [3, 4]and thus gives a first glimpse of an electric hyperonform factor . Second, chiral SU(3) can be subject tolarge kaon/eta loop corrections, and the form fac-tors offer another window to study the correspond-ing convergence properties . They might thus indicatewhether or not the strange quark can be consideredlight and lead to a better understanding of SU(3)flavor symmetry breaking . Since the chiral expan-sion of the form factors is well under control in thetwo-flavor case, one can expect to encounter a rea-sonably well-behaved series also in the presence ofthe strange quark. This expectation is borne out bythe results presented in this paper. Third, one canalso address some questions concerning strangenessin the nucleon, more precisely, the role of kaon loopswhich in simplemodels let one expect sizeable contri-butions of strange operators . Fourth, a knowledge ofcertain hyperon form factors, is mandatory to gain anunderstanding of kaon photo- and electroproductionoff nucleons and light nuclei as measured at ELSAand TJNAF. In addition, these form factors have al-ready been calculated in the so-called heavy-baryonapproach, which is a particular limit of the regu-larization procedure employed here . A direct com-parison with the results of that approach can shedfurther light on the dynamics underlying the non-perturbative baryon structure, in particular the roleof recoil corrections . As a final by-product, we canalso readdress the issue of the convergence of thechiral expansion for the magnetic moments, which ismuch discussed in the recent literature .We have studied the electromagnetic form factors ofthe baryon octet in a manifestly Lorentz invariantform of baryon chiral perturbation theory to one-loop (fourth) order employing the so-called infraredregularization of loop graphs [5] . The pertinent re-sults of our investigation can be summarized as fol-lows :

Baryon form factors in chiral perturbation theory

Bastian Kubis and Ulf-G. Meißner

90

(2) To fourth order, only two LECs affect the elec-tric radii . These can be fixed from the mea-sured neutron and proton radii . Always using the empirical magnetic moments in theFoldy term, we have shown that the fourthorder corrections to the electric radii are as-tonishingly small, and so are the resulting un-certainties. The prediction for the E- radius,(r,-)1/2 = 0.67 ± 0.03 fm, agrees with the re-cent result from the SELEX collaboration [4] .Thepion-kaon mass difference leads to sizeabledeviations from flavor SU(3) symmetry .

We have argued that the chiral expansion ofthemagnetic moments in the relativistic scheme isambiguous at third order, such that no clearstatement can be made whether or not conver-gence is improved in comparison to the heavy-baryon scheme . At fourth order, due to thepresence of seven low-energy constants, onecan only predict the A-E° transition moment,YAEO = 1.61±0.01 n.m., in stunning agreementwith the empirical value.

The magnetic radii cannot be predicted so pre-cisely. Again, one finds large SU(3) breakingdue to loop corrections . In particular, the mag-netic radius of the E- is largest (as it is alsofound in lattice gauge theory studies) .

(4) For the electric form factors of the charged par-ticles, the pure chiral representation providestoo little curvature . With vector mesons included as in [1], the QZ-dependence of variouscharged form factors is given up to virtualitiesof QZ .-_ 0.3 GeV2 . For the neutral particleswe find in general a large cancellation of thesevector meson contributions, and the resultingform factors for the neutral hyperons displayless curvature than the neutron one . We donot observe any sizeable effects in the electricproton and neutron form factors when goingfrom SU(2) to SU(3) . Again, the correspond-ing magnetic form factors cannot be predictedso precisely.

References:[1] B. Kubis and Ulf-G. Meißner, hep-ph/0007066,

Nucl . Phys . A679 (2001) 698 .[2] T. Becher and H. Leutwyler, Bur. Phys . J . C9

(1999) 643.[3] M. Adamovich et al ., Eur. Phys . J . C8 (1999)

59 .[4][5]

I . Eschrich et al ., hep-ex/9811003 .B . Kubis and Ulf-G . Meißner, hep-ph/0010283,Bur. Phys . J . C (2001), in print .

Low energy analysis of the nucleon electromagnetic form factors

The electromagnetic structure of the nucleon as re-vealed in elastic electron-nucleon scattering is pa-rameterized in terms of four form factors, either theDirac (Fl) and Pauli (F2) or the Sachs (electric, GE,and magnetic, GM) ones . The understanding oftheseform factors is of utmost importance in any theoryor model of the strong interactions . Abundant dataon these form factors over a large range of momen-tum transfer already exist, and this data base willconsiderably improve in the few GpV region as soonas further experiments at CEBAF will be completedand analyzed . In addition, experiments involving po-larized beams and/or targets are also performed atlower energies to give better data in particular forthe electric form factor of the neutron, but also forthe magnetic proton and neutron ones . Such kinds ofexperiments have been performed or are under wayat NIKHEF, MAMI, ELSA, MIT-Bates and otherplaces . Clearly, theory has to provide a tool to in-terpret these data in a model-independent fashion.For small momentum transfer, this can be done inthe framework of baryon chiral perturbation theory(ChPT), which is the effective field theory of theStandard Model at low energies .We have studied the electromagnetic form factors ofthe nucleon [1] in a manifestly Lorentz invariant formof baryon chiral perturbation theory [2] to completeone-loop (fourth) order. This scheme is based on theso-called "infrared regularization" of loop graphs,and one is able to set up asystematic power countingscheme [2], based on the observation that contribu-tions generated by large loop momenta can be sys-tematically absorbed in local contact terms of the ef-fective Lagrangian . Being relativistic, this approachleads by construction to the correct behavior of thespectral functions in the low energy domain . Fur-thermore, it is expected to improve the convergenceof the chiral expansion because it automatically re-sums all recoil-type corrections - p/m through theDirac propagator for the nucleon. It is also impor-tant to stress that the results obtained previously inthe heavy baryon approach [3, 4] can be straightfor-wardly deduced from the framework employed here,shedding some more light on these previous results .The pertinent results of our investigation can besummarized as follows [1] :* To fourth order, the neutron and proton electricform factors each contain one low-energy constantwhich can be fixed from the empirical informationon the corresponding charge radii . This gives a gooddescription of the neutron charge form factor up tofour-momentum transfer squared of Q2 = 0.4 GeV2,see fig.1, and, furthermore, exhibits convergence inthat the corrections when going from third to fourthorder are small. This is in contrast to the heavybaryon expansion and can be traced back to the

Bastian Kubis and Ulf-G. Meißner

91

proper resummation of the recoil terms in the rela-tivistic expansion . For the electric form factor of theproton, the one-loop representation gives too littlecurvature and thus deviates from the data alreadyat Q2 - 0.2 GeV2 , similar to the heavy baryon de-scription . However, no large fourth order correctionsare found below Q2 = 0 .4 GeV2 .

Figure 1: The neutron electric form factor in rela-tivistic baryon chiräl perturbation theory (solid lines,IR) to third and fourth order . For comparison, theresults of the heavy baryon approach are also shown(dashed, HB) . Also given is the result of the disper-sion theoretical analysis (dot-dashed curve, DR) .

* To third order, the momentum dependence of themagnetic proton and neutron form factor is givenparameter-free . The 1/m corrections present in ourapproach worsen the prediction for the magneticradii based on the leading chiral singularities, likee.g . in the heavy baryon approach . The leading chi-ral limit behavior is not agood approximation for theGoldstone boson contribution to the magnetic radii(as it is often stated) . At fourth order, the magneticradii can be fixed due to the appearance of two coun-terterms . Again, there is not enough curvature in theone-loop representation and one observes large cor-rections when going from third to fourth order al-ready at QZ - 0.1 GeV2.9 We have demonstrated explicitly that the spectralfunctions of the isovector form factors have the cor-rect threshold behavior as deduced from analyticityand unitarity. The strong momentum-dependence ofthese spectral functions close to threshold is due tothe branch point singularity on the second Riemannsheet inherited from the 7r7r -+ NN P-wave partialwave amplitudes . This makes explicit that IR of loopintegrals leads to the correct analytic behaviour inthe low-energy domain .* We have included the low-lying vector mesonsp, w, 0 in a chirally symmetric manner based onan antisymmetric tensor field representation . This

does not introduce any new parameters since these(masses and coupling constants) are taken from thePDG tables and from a dispersion theoretical anal-ysis [5] . Refitting the previously defined low-energyconstants by subtracting the vector meson contribu-tion, we find a good description of all four form fac-tors already at third order, with small fourth ordercontributions, which further improve the theoreticaldescription, see figs.2,3,4 . In particular, we demon-strate that the vector meson contributions cancel toa large extent in the neutron charge form factor, thussolidifying the result obtained in the chiral expan-sion . We also note that the novel results from Jef-ferson Lab for the neutron magnetic form factor forQZ = 0 .1 and 0 .2 GeV2 [6] agree perfectly with thechiral plus vector meson prediction .

Figure 2: The proton electric form factor in relativis-tic baryon chiral perturbation theory including vec-tor mesons to third (dashed) and fourth (solid) order,divided by the dipole form factor . For comparison, weshow the dispersion theoretical result (dot-dashedcurve) and the world data available in this energyrange.

Figure 3: The proton magnetic form factor in rela-tivistic baryon chiral perturbation theory includingvector mesons to third (dashed) and fourth (solid)order, divided by the dipole form factor . For com-parison, we show the dispersion theoretical result(dot-dashed curve) and the world data available inthis energy range .

" The inclusion of vector mesons allows to investi-gate the resonance saturation hypothesis for these

92

Figure 4: The neutron magnetic form factor in rela-tivistic baryon chiral perturbation theory includingvector mesons to third (dashed) and fourth (solid)order, divided by the dipole form factor . For compar-ison, we show the dispersion theoretical result (blackdot-dashed curve) and the world data available inthis energy range.

couplings. We find that the couplings related to themagnetic moments and the isoscalar radii are al-most completely saturated by the low-lying vectormesons . This is, however, not the case for the low-energy constants entering the isovector radii . Thiscan be traced back to the fact that while the w andthe 0 already give a good description of the isoscalarform factors, for the isovector ones one has to in-clude higher mass states than the p, in agreementwith findings from dispersion theory.Obviously, the same method is being used to investi-gate the so-called strange form factors of the nucelonas well as the hyperon electromagnetic structure.

References :

B . Kubis and Ulf-G. Meißner, hep-ph/0007056,Nucl . Phys . A 679 (2001) 698 .

[2] T. Becher and H. Leutwyler, Eur. Phys . J. C9(1999) 643 .

V. Bernard, N. Kaiser, J. Kambor, and Ulf-G . Meißner, Nucl . Phys . B388 (1992) 315.[4] V. Bernard, H.W. Fearing, T.R . Hemmert, andUlf-G . Meißner, Nucl . Phys . A635 (1998) 121 ;(E) Nucl . Phys . A642 (1998) 563.

P. Mergell, Ulf-G. Meißner, and D. Drechsel,Nucl . Phys . A596 (1996) 367.

[6) W. Xu et al ., Phys . Rev. Lett . 85 (2000) 2900 .

Ordinary and radiative muon capture on the proton and the induced pseudoscalar

Ordinary and radiative muon capture on the pro-ton at rest can be considered as an excellent testingground for our understanding of dynamical and ex-plicit chiral symmetry breaking in QCD. This stemsfrom the fact that the typical momentum transferin these reactions is very small, of the order of themuon mass, and one therefore can apply effectivefield theory methods, in particular baryon chiral per-turbation theory . Ordinary muon capture (OMC),p- + p -4 v1, -I- n, allows to measure the so-calledinduced pseudoscalar coupling constant, gp . The ex-isting data are in agreement with the pion pole pre-diction, gp = 8.9 and also the one-loop chiral per-turbation theory result, gp = 8.4±0.2 [1] but too im-precise to discriminate between these numbers . Ra-diative muon capture (RMC), y- -I- p -4 v. -f- n +,y,has a variable t and one can get up to t = m2, atthe maximumphoton energy of about k - 100 MeV,which is very close to the pion pole . This amounts ap-proximately to a four times larger sensitivity to gp inRMC than OMC. However, this increased sensitivityis upset by the very small partial branching ratio inhydrogen and one thus has to deal with large back-grounds. Precisely for this reason only very recentlya first measurement of RMC on the proton has beenpublished [2] . The resulting number for gp, whichwas obtained using a relativistic tree model includ-ing the A-isobar, came out significantly larger thanexpected from OMC, gRMC = 12 .35 ± 0.88 ± 0 .38 =1.46gpHPT . It should be noted that in this analy-sis the momentum dependence is entirely given interms of the pion pole and the induced pseudoscalarcoupling is obtained as a multiplicative factor fromdirect comparison to the photon spectrum and thepartial RMC branching ratio (photon energies largerthan 60 MeV) . It was also argued in [2] that theatomic and molecular physics related to the bindingof the muon in singlet and triplet atomic lip and or-tho and para pyp molecular states is sufficiently wellunder control. To shed light on this puzzling result,we have studied OMC and RMC in heavy baryonchiral perturbation theory as well as in an effectivefield theory including the delta isobar, in which thenucleon-delta mass splitting is considered as an ad-ditional small parameter (the small scale expansion,SSE) [3] . The pertinent results of our investigationcan be summarized as follows:- To third order in the small scale expansion, ordi-nary muon capture is almost not affected by 0(1232)isobar effects. The only effect comesvia the Pauli ra-dius and is extremely small. The NLO contributionto the total capture rate amounts to a 25% correctionof the leading term . This is in agreement with naivedimensional counting, which lets one expect correc-tions of the size mm/Ax. This calculation involvesvery few and well-controlled parameters . We arguedthat a formula derived from a relativistic calculation

V . Bernard (Strasbourg), T.R . Hemmert, Ulf-G. Meißner

93

and extensively used in the literature does not holdin the modern view point of power counting . We havestressed the importance of the upcoming PSI exper-iment.- To second order in the small scale expansion, wehave considered radiative muon capture. 0(1232) re-lated effects only appear at NLO and its effects onthe total capture rate and the photon spectrum areof the order of a few percent. The smallness of theA(1232) contributions is due to a combination of ef-fects as discussed in [3] . This agrees with earlier find-ings in a more phenomenological approach . Isobareffects can therefore not resolve the discrepancy be-tween the TRIUMF measurement for the partial de-cay width r(w > 60 MeV) and the theoretical predic-tions. We have, however, pointed out severe loopholesconcerning the extraction ofgp as done in ref. [2], oneof them being the contradiction with the OMC data .In our opinion the most probable explanation of thediscrepancy is a combination of many small effects,see fig . l.

form factor

Figure 1 : Photon spectra for RMC for theatomic/molecular input as used in the TRIUMFanalysis . Solid line : Prediction of the small scale ex-pansion to order e2 . Dash-dotted line : Same as thesolid line but with gp scaled by a factor 1.5 . Dashedline : Various small modifications as explained in [3] .Dotted line : Same as the dashed line but using theneutral instead of the charged pion mass .

- The induced pseudoscalar form factor measuredin charged pion electroproduction is not very welldetermined, but clearly is in agreement with theone-loop chiral perturbation theory prediction [1] .A more precise measurement for small invariant mo-mentum transfer squared as proposed at MAMI iscalled for.References :

[1] V . Bernard, N. Kaiser and Ulf-G . Meißner,Phys . Rev. D50 (1994) 6899 .

[2]

G. Jonkmans et al ., Phys . Rev. Lett . 77 (1996)4512 ; D.H . Wright et al ., Phys . Rev . C57 (1998)373.

[3]

V. Bernard, T.R. Hemmert and Ulf-G . Meißner,Nucl . Phys . A (2001) in print, hep-ph/0001052 .

Eliminating the high momentum components from realistic NN potentials

Recently the two-nucleon potential based on themost general chiral effective pion-nucleon La-grangian has been applied at first time to the three-(3N) and four-nucleon (4N) systems [1] . It wasshown, that the chiral forces are very well suitedto describe low-energy observables in those systems.In particular, the predicted nd scattering observ-ables agree rather well with the data and their de-pendence on the momentum cut-off, chosen in thetwo-nucleon (2N) system, is rather mild . The pre-dicted 3N and4N binding energies are-all in the samerange as for standard NN potentials, but show some-what larger cut-off dependence . An important out-come of this study is an improvement of the so-calledAy-puzzle in the low-energy elastic nd scattering .The predicted values of the nd analyzing power Ayare rather close to the experimental values and thusthe Ay-puzzle is absent at the considered next-to-leading order (NLO) . It is, of course, quite interest-ing and important to understand the mechanism ofsuch an improvement. Clearly, the NLO chiral po-tential is substantially different from the standardones . It includes the leading two-pion exchange con-tributions, which are usually not present in the re-alistic forces . Furthermore, the potential is stronglynon-local . Another important difference is that itis much "softer" and vanishes for high relative mo-menta. Consequently, the range of integration in therelative momenta in the 3N Faddeev equation couldbe very much reduced from its typical value for re-alistic forces . In this study we want to investigatethe effects of the high momentum components of therealistic NN forces on the many-body low-energy ob-servables . This might shed light on the mechanism ofimprovement for the Ay .

It has been shown in [2] how to construct the effectivelow-momentum theory from a given 2N interaction,which leads to the same S-matrix below the momen-tum cut-of A. To be more precise, one applies theMethod of Unitary Transformation (MUT) to decou-ple the subspaces of low (below A) and high (aboveA) momenta, i .e . to block-diagonalize the Hamilto-nian with respect to those subspaces. Since we areinterested in the low-momentum theory and the twosubspaces are not coupled any more, one chooses theeffective potential as the low-momentum componentof the transformed potential . Consequently, the ef-fective potential vanishes for momenta larger thanA. Choosing the same values of the cut-off as in thecase of the chiral NLO potential we obtain the effec-tive realistic potential defined in the same momen-tum region as the chiral one.

In [2] the MUT has been applied to a toy S-wavepotential of the Malfiiet-Tjon type . The unitary op-erator U has been parametrized in terms of anotheroperator A, which has to satisfy the following non-

E. Epelbaum, H. Kamada, and Ch. Elster

linear equationA(H - [H, A] -AHA)r7 =0 . (1)

Here H is the Hamiltonian and 77 (A) is the projec-tor onto the subspace of low (high) momenta. Wehave generalized the formalism described in [2] toarbitrary partial wave and applied it to several re-alistic potentials . In Fig. 1 we show the NLO chiralpotential and the effective Bonn B potential in themomentum space, corresponding to the momentumcut-off A = 500 MeV (here and below c = 1) . Notethat both potentials are strongly non-local. It is now

94

.Fig . 1: Chiral (left panel) and effective Bonn B (rightpanel) potentials V(p,p') [GeV-2] versus pand p' in GeV in the 'So channel.

possible to separate the effects of the high momen-tum components to various low-energy observablesin the 3N and 4N systems. As the first application, wehave calculated the triton binding energy for the ef-fective Nijmegen 93 potential, see Fig. 2. The bindingenergy was found to increase if the cut-off decreasesto 2 fm-1 . This might be an indication that less 3Nforce is needed after integrating out high momentumcomponents . However, to draw the final conclusionone needs to calculate various scattering observables .

W

References :

-7.6

-7 .8

-8

-8.2

-8.4

-8 .62 2.5 3 3.5 4

A [fm-1 ]4.5 5

Fig. 2: Triton binding energy E versus the cut-off Afor the Nijmegen 93 potential (solid line) com-pared with its original value (dashed line) .

(1] E.Epelbaum et al ., nuci-th/o0o70S ?,[2] E.Epelbaum et al ., Nucl . Phys . A645 (1999) 413.

Charge-dependent nucleon-nucleon potential from chiral effective field theory

It is well established that the nucleon-nucleon in-teraction is charge dependent (denoted CIB) andalso that charge symmetry is broken (called CSB) .Within QCD (plus QED), CSB and CIB are of coursedue to the different masses and charges of the upand down quarks . Such isospin violating effects canbe systematically analyzed within the framework ofchiral effective field theories . Here, we present such acharge-dependent potential form effective field the-ory [1] . Based on a modified Weinberg power count-ing, we have systematically included strong and elec-tromagnetic isospin violation in a chiral two-nucleonpotential at next-to-leading order (NLO) . Strongisospin violation due to mu :A and can easily be incor-porated by means of an external scalar source . Theelectromagnetic effects due to hard photons are rep-resented by local contact interactions . Soft photonsappear in loop diagrams and also generate the long-range Coulomb potential . The corresponding classi-fication scheme for the various contributions to CIBand CSB based on the extended power counting atLO and NLO is given in table 1, in terms of the finestructure constant a and the quark mass differencee-and-mu .

The resulting potential consists of two distinctpieces, the strong (nuclear) potential includingisospin violating effects and the Coulomb poten-tial . The nuclear potential consists of one- and two-pion exchange graphs (with different pion and nu-cleon masses), 7ry exchange diagrams and a set oflocal four-nucleon operators. Since the nuclear ef-fective potential is naturally formulated in momen-tum space, we use a momentum space matchingprocedure to incorporate the correct asymptoticalCoulomb states . The necessary regularization of thepotential is performed on the level of the Lippmann-Schwinger equation, using a sharp momentum spacecut-off A. The low-energy constants accompanyingthe contact interactions and the cut-oft' A are de-termined by a simultaneous best fit to the S- andP-waves of the Nijmegen phase shift analysis in thenp and the pp systems for laboratory energies below50 MeV. This allows to predict these partial wavesat higher energies and all higher partial waves. Mostphysical observables come out independent of thecut-off for A between 300 and 500 MeV . The upper

Markus Walzl, Ulf-G. Meißner, Evgeny Epelbaum

95

Figure 1 : 3Po phase shifts for the np and pp systemsim comparison to the Nijmegen PSA.

limit on this range is determined by the pp interac-tions . A typical result for 3P0 is shown in fig.l . Wehave studied in detail the range expansion for thenp and the pp system . We have dissected the var-ious contributions to CIB in the scattering length,reconfirming the importance of the pion mass differ-ence in the OPE. The TPE contribution is smallerin size but of opposite sign, and also strongly cut-offdependent . We have also studied the nn system, per-forming effective range fits based on the "standard"value for ann = -18.9 fm and using the most recentresult from deuteron break-up, an,, = -16.4 fm . Thisleads to rather different physics underlying chargesymmetry breaking, see also fig.2 .

References :

's0

np

---- nn (Bonn 99)--- nn (Staus 89)

" Nijm np 93o Nijm 93 pp

Figure 2 : Range fit for the nn ISO phase shift basedon different scattering lengths (ann = -18.9 fm:long-dashed line, ann = -16 .4 fm : short-dashed line)in comparison to the np and pp phases .

[1] M. Walzl, Ulf-G. Meißner and E. Epelbaum,nucl-th/0010019 .

Order Para . ContributionLO a Pion mass difference in OPE

a Coulomb potentialNLO a Pion mass difference in TPE

a 7ry-exchangea four-nucleon contact

interaction - (NtT3N)2

E four-nucleon contactinteraction - (NtT3N)(NtN)

Three and four nucleon systems from chiral effective field theory

E. Epelbaum, H. Kamada, A. Nogga (Bochum), H. Witala (Krakau), W. Glöckle (Bochum), Ulf-G. Meißner

Chiral effective field theory can be applied succes-fully to the pion and the pion-nucleon systems . Forprocesses involving more than one nucleon, the ap-pearance of shallow nuclear bound states requiresan additional non-perturbatioe resummation . Wein-berg [1] suggested to apply power counting to thetwo-nucleon (NN) potential based on time-orderedperturbation theory (TOPT), generating bound andscattering states from the Schrödinger or Lippmann-Schwinger (LS) equation . In [2] it was shown how tomodify this power counting to generate an energy-independent hermitean potential by means of theFST-Okubo projection formalism . In addition, theso constructed wave functions are fully orthonor-mal, whereas in TOPT this only holds to the or-der one is working. The NNLO np potential wasconstructed in [3] and shown to reproduce most npphase shifts to good precision up to pion productionthreshold . For that, the LS equation was solved usinga momentum-space regulator in harmony with theunderlying symmetries . Typical cut-off values rangefrom 500 MeV to 1 GeV . In particular, the two S-waves are cut-off independent and as precisely givenas in the so-called realistic potentials . The D-wavesshow some cut-off dependence which can be curedat N'LO. However, the most important 3Di phase isvery stable against changes in A. Similarly, with noparameter tuning the deuteron properties can be de-scribed fairly accurately. As in all modern potential,the quadrupole moment calculated from the one-body currents comes out smaller than the empir-ical value. The construction of the pertinent two-body operators is in progress . Next, we have appliedthe NLO np potential to systems of three and fournucleons[4] . At this order, one has no three-nucleonforces (3NF) and thus obtains parameter-free pre-dictions . For changing the cut-off between 540 and600 MeV, the 3H and 3He binding energies vary be-tween -7.55 . . . - 8.28 and -24.0 . . . -28.0 MeV, re-spectively, showing the need for some small 3NF. Itis also important to note that the kinetic energiesin 3N and 4N bound states are smaller and two-nucleon correlation functions are smoother than forstandard NN forces, indicating a change of the wavefunctions . 3N scattering can be solved exactly, in thefigure we show the result for elastic nd scattering at3 and 10 MeV. While for the cross section (and alsothe tensor analyzing powers T2k) the results usingthe chiral force are in agreement with what is foundfor high precision potentials like CD-Bonn, we finda clear improvement in the analyzing power Ay , seeFig-l.This clearly shows that the chiral NN forcesare different from the ones based on "realistic" po-tentials . We also stress that we perfectly reproducethe np analyzing powers at 3 and 12 MeV, which isan important consistency check. The difference ofthechiral and the "standard wave" functions can also be

seen in the exact numerical solution of the Faddeev-Yakubowsky equations, one can reduce the cut-offsfor the momentum integrations in the relative mo-menta from their typical values 8 fm -1 arising withstandard potentials down to 4 fm -1 without chang-ing the result .

96

0

0 .02

0

-042

-0.04

0 .06

0 .02

0 .01

0

0

-0.01

-0 .02

-0.00

References :

0

0.1

0

0

-0.10

-0.1

[T20

0 45 90 135 100 0 46 60 105 160

0 (deg]

0 (deg(

Figure 1 : nd elastic scattering observables atEn = 3MeV (left column) and En, = 10 MeV (rightcolumn) for the chiral force (A = 540 MeV, dottedcurve; A = 600 MeV, dashed curve) and CD-Bonn(solid curve) .

These very first results using chiral NN forces in 3Nand 4N systems are very promising . Even though werestricted ourselves to NLO, our results already showthat these effective chiral forces are very well suitedto describe also low energy properties of nuclear sys-tems beyond A-_ 2. Most importantly, the Ay puzzleseems to get resolved in a consistent fashion . Clearly,a NNLO analysis is needed to further quantify thesepromising results and to pin down the 3NF system-atically.

[1] S. Weinberg, Nucl . Phys . B363 (1991) 33-[21 E. Epelbaoum, W. Glöckle and

Nucl . Phys . A637 (1998) 107.[3] E. Epelbaum, W. Glöckle and

Nucl . Phys . A671 (2000) 295 .[4]

E. Epelbaum et al ., nucl-th/0007057 .

Ulf-G. Meißner,

Ulf-G . Meißner,

400

100

2.00

0

25

0.20.06

0.04

0.02

Two-nucleon scattering at intermediate energies of afew hundred MeV requires quite a few angular mo-mentum states in order to achieve convergence ofe.g . scattering observables . This is even more true forthe scattering of three or more nucleons upon eachother. An alternative approach to the conventionalone, which is based on angular momentum decompo-sition, is to work directly with momentum vectors,specifically with the magnitudes of the momenta andthe angles between them. We formulated and numer-ically illustrated [1] this alternative approach for thecases of NN scattering using two realistic interac-tion models, the Bonn-B [2] and the Argonne AV18[3] potentials . The momentum vectors enter directlyinto the scattering equation, and the total spin ofthe two nucleons is treated in a helicity represen-tation with respect to the relative momenta of thetwo nucleons . Using rotational and parity invarianceone fins in the triplet case S=1 a set of two coupledLippmann-Schwinger equations for each parity andeach initial helicity state . Because ofsymmetry prop-erties only two of the originally three initial helicitystates need to be considered . In the singlet case S=0there is only one single Lippmann-Schwinger equa-tion for each parity. Those equations (uncoupled andcoupled) are two-dimensional integral equations intwo variables for the half-shell t-matrix and in threevariables for the fully-off-shell t-matrix, namely twomagnitudes of momenta and one angle.

Nucleon-Nucleon Scattering in a Three-Dimensional ApproachI. Fachruddin, Ch. Elster, W. Glöckle

Fig. 1 : do--j-. as a function of 0 for qo=375 MeV/c cal-culated from the Bonn-B potential.

We demonstrated the feasibility and accuracy ofour three-dimensional formulation by projecting theon-shell t-matrix elements on angular momentumstates and compare the resulting phase-shifts withthose obtained from standard partial wave projectedLippmann-Schwinger equations. The agreement isvery good and demonstrates the numerical reliabilityand accuracy of out method. In Fig. 1 we display thedifferential cross section at Blab=300 MeV togetherwith partial wave sums for selected total angular mo-menta imax "

97

Fig. 2: The on-the-energy-shell t-matrix ampli-tudes as given in the form of the six in-dependent amplitudes J(mim2JTJmlm2)1 2la(viv2mimigoql Tlva.v2mim2go)a1 2 ,where m _ ±2 . We show the amplitudes1(+ + ITI + +(12 and 1(+ + ITI _ _( 12 inunitsl0-14 MeV-4 as function of energy andc.m . scattering angle cos 0.

In Fig. 2 we show a selection of the six independentphysical amplitudes as function of the laboratory en-ergy and the c.m . scattering angle. Though both po-tentials are only meant to be applied below the pionproduction threshold, we show the on-shell ampli-tudes up to 1 GeV. Since we do not work with par-tial waves, a calculation at higher energies takes thesame effort as one at very low energies . We emphasizethat the here developed scheme is algebraically verysimple to handle provided potentials are given in anoperator form . This is e.g . the case for all interac-tions developed within a field theoretic frame work .In addition, the solution of two-dimensional integralequations does not pose any difficulty for moderncomputers .

References :[1] I . Fachruddin, Ch. Elster, and W. Gl8ckle,

Phys.Rev.C62, 044002 (2000) .[2] R. Machleidt, Adv. Nucl . Phys . 19, 189 (1989)(3] R. B. Wiringa, V. G . J. Stoks, R. Schiavilla,

Phys . Rev. C51, 38 (1995) .

Spin Configurations in the Deuteron

I. Fachruddin, Ch. Elster, W. Glöckle

Fig. 1 : The probability density p4(q) in units 10-10McV-3 for one nucleon having spin up andthe other having spin down . The contoursrepresent equidensity lines along a verticalsection in the x-z plane.

As an object with internal structure it is tempting toinvestigate the deuteron properties three dimension-ally. To that aim we study the deuteron propertiesin a representation based on the total helicity of thetwo-body system taken along the relative momentumof the two particles [1] . Though originally developedfor describing NN scattering [2], the method is gen-eral and can be used to solve bound state problemsas well . We introduce deuteron wave function com-ponents in the helicity basis. They depend on themagnitude q of the relative momentum and the an-gle 0 of the relative momentum q to the z axis andare solutions of a set of two coupled eigenvalue equa-tions .We derived an `operator form' of the deuteron wavefunction to obtain insight into the analytical an-gular behavior of those wave function components .The operator form is also an ideal tool to expressprobabilities for different spin configurations withinthe deuteron . As an example we choose a polarizeddeuteron with Md = 1, where Md is the projectionof the total angular momentum along a chosen axis,e.g. the z-axis . Cases of interest are if (1) both nu-cleons have their spins up, (2) both nucleons havetheir spins down, (3) one nucleon has spin up andthe other has spin down, (4) one nucleon has spinup and the other has arbitrary spin orientation and(5) one nucleon has spin down and the other hasarbitrary spin orientation. As examples we give theprobability density for one nucleon having spin upand the other having spin down

piI (q)

qfd*(q)2 [1 + ~z(1)] 2[1 _ ~z(2)]

d(q)

and the probability density for both nucleons havingspin down

98

39 cos2 9 sine 6,02 (q)

p4 (q)

=

~ä'*(q) 2 [1 _" ß' z (1)] 2 [1- ßz(2)] Td(d)

32-7r sin4 8 ' 2 (q)

References :

Here 02 (q) denotes the usual deuteron D-wave,whereas '1'd(q) describes the full deuteron state withMd = 1 . For the case where the spins of the two nu-cleons point into opposite directions, the probabil-ity density is shown in Fig. 1 . According to Eq. (1),this density is given solely by the deuteron D-waveand a function of the angle 8 . It has four peaks ofequal height in each quadrant of the q., - q,-planeat Jgxi = JgzI = gmax cos(4) . Rotating the verticalsection in the x-z-plane around the z-axis will reveala double toroidal structure.

Fig. 2: Two selected equidensity surfaces of the prob-ability density pfiy (q) for one nucleon havingspin up and the other having spin down.

For the image in Fig. 2 two equidensity surfaces arepicked and rotated around the z-axis, resulting ina double torus being cut open vertically. The innertubes represent surfaces of higher density comparedto the outer ones . The shape is characteristic for aspherical harmonics with l = 2,m = 1 . A measure-ment on the deuteron at rest would see in the max-ima the two nucleons with momenta back to backpointing at 0 = 45° .

[1] I. Fachruddin, Ch. Elster, andW. Glöckle, `NewForms of Deuteron Equations and Wave Func-tion Representations', nucl-th/0101009 and sub-mitted to Phys. Rev. C

[2] I. Fachruddin, Ch. Elster, and W. Glöckle, Phys .Rev. C 62 , 044002 (2000) .

Theoretically as well as experimentally it is well es-tablished that the one-pion-exchange (OPE) pro-vides the long range part of the nucleon-nucleon(NN) interaction. The offshell behavior of the OPEdepends on whether a pseudoscalar (ps) or pseu-dovector (pv) pion-nucleon coupling is used . In ad-dition, there has always been some ambiguity aboutoff-shell effects in NN potentials, which have beencharacterized by Friar [1] into three types: (i) thosecaused by an energy dependent potential which oc-cur naturally when expanding energy denominatorsin Schr6dinger perturbation-theory treatments of theexchanged meson; (ii) those arising from unitarytransformations of field variables used in the La-grangians, and (iii) those due to different choices ofrelativistic Hamiltonians . Here we want to concen-trate on the different off-shell forms that arise fromdifferent forms of the coupling . We derive the pv-coupling in the framework of time-ordered perturba-tion theory and compare the off-shell behavior of thepotential to the one obtained form ps-coupling.For the pv-coupling the 7rN vertex is given by

In time-ordered perturbation theory one needs to cal-culate the matrix elements of the Hamiltonian den-sity, which is obtained as

71

Pseudovector NN7r Coupling in Time-Ordered Perturbation Theory

LNN7r

74571,f~m,r

2=

W0 - ,CNN7r'+. 2 ~MW i'i5'70~~

(2)

In the derivation one needs to consider that the timederivative of the meson field in Eq. (1) introducesan additional contact term in the interaction part of7l . Thus, the NN7r quasipotential is represented bythe following diagrams The contact term is necessary

VPvNN,r(foq1 , z) _

G. Caia, J.W. Durso, Ch. Elster, J. Hardenbauer

Fig. 1: Diagram contributing to the OPE in pv cou-pling. The last diagram represent the contactterm.

to obtain the correct Feynman amplitude in the on-shell limit. Evaluating the diagrams in the c-m. frameleads to

99

E99"Eq -w) [(75)1(75)2(27 .)3 w(z -(Eg' -

2mBI)

[(7570)1(75)2 + (75)1(757°)2]

E , E 2( 44m2

e) ('Y ^10)1('YS 'Y °)2I

2

+

(27r)3 4m2 (757°)1(757°)2

(27.)s 4m2 (z -Eq, - E9 - w)(757 °)1 (757°)2

Here z = 2Ego, the total energy of the NN system,

vertices of nucleons 1 and 2 are taken between freepositive energy Dirac spinors . For the pion couplingconstant we used g,2, = 14.6 together with the re-lation g,2 /4m2 = f12r/mI. and employed a cutoff ofdipole type with a cutoff mass A=1750 MeV. Thecontributions to the NN7r-potential VNN,(q, q0 , Eq0)in the 'So state are shown in Fig. 2 for q0=350 MeV.The first line of the right hand side of Eq. (3) repre-sent the ps-coupling and is represented by the dash-dotted line . All terms proportional to the propagatorare summed up in the dashed line (a), then succes-sively the contribution of the contact term (ct) andthe term given in the last row of Eq. (3) are added toobtain the full result for the pv-coupling. Though thetwo different couplings give on-shell identical results,their off-shell extrapolation differs considerably.

References :

q, = 350MeV

Fig. 2: OPE Potential in the 'So state . The dash-dotted line (ps) represents the calculationwith pseudoscalar coupling, the dashed line(a) all contributions to the pseudovector cou-pling proportional to the meson propagator,for the dotted line (ct) the contact termis added to the previous contributions. Thesolid line (pv) represents the full pseudovec-tor OPE potential.

[1] J.L . Friar, Phys. Rev. C60, 034002 (1999) .

Some results presented in Ref. (1] suggest an almostperfect factorization of the on-shell momentum de-pendence of the half-shell NN S-wave T matrix, i.e .

This means that the ratio T(k, q)/T(k, k) does notdepend on the on-shell nucleon momentum k, but isonly a function of the off-shell momentum q .This scaling property of. the half-off-shell matrixT(k, q) provides a computational simplification inevaluating the final state NN interaction, that ef-fects meson production in nucleon-nucleon collisionsnear threshold . Furthermore, the scaling allows quitestraightforward evaluation [1] of the beam energy de-pendence of the meson production cross section. Thecrucial question is up to what maximal momenta kand to what accuracy can one use such a scalingproperty of the T matrix .

T(k,q) ;z~ T(k,k)T(q).(1)

Scaling property of the half-off-shell T matrix

A. Sibirtsev, Ch. Elster and J. Haidenbauer

q (GeV/c)

Figure 1: Scaling of the on-shell momentum depen-dence for the half-off-shell T matrix obtained fromthe CD-Bonn model. The results are shown for theon-shell nucleon momenta 1<k<100 MeV/c.

Here we investigate the scaling property of thehalf-off-shell T matrix obtained from the CD-Bonnmodel [2] . The ratio RT(k, q)IRT(k, k) for the ISOnp interaction is shown in Fig.l as a function of q .The set of lines indicates the ratio evaluated for theon-shell nucleon momenta from 1 to 100 MeV/c.If the scaling property would hold exactly, thecurves shown in Fig. 1 for the different on-shell

100

momenta k should lie on top of each other. Forthe CD-Bonn model scaling is approximately full-filled, as can be seen in Fig.l . Within the range1<k<100 MeV/c the deviations are roughly around10%. Indeed, in this range the q-dependence of theratio RT(q, k)/NT(q, q) can be approximated by thesimple function

with the off-shell nucleon momentum q given inGeV/c.However, the scaling of the T(q, k) IT (q, q) ratio isviolated substantially for on-shell nucleon momentaabove 120 MeV/c, as is illustrated by the Fig.2 .

exp[-3.28g2) cos[3.9q],

(2)

3

0

-2

References :

q (GeV/c)

Figure 2: Violation of the scaling of the half-off-shellT matrix at the momenta 120<k<300 MeV/c.

Since the final on-shell nucleon center-off-mass mo-mentum is related to the excess energy E for the me-son production as k- EmN, the discussed scalingcan be applied up to the E-12 MeV, which corre-sponds to the energy range available for the COSY-11 experiments.

[1] J . Adam Jr . et al ., Nucl . Phys . A 631 (1998)570, Phys . Lett . B 407 (1997) 97 .

(2] R. Machleidt, Phys. Rev. C 63 (2001) 024001 .

Chiral dynamics in the presence of bound states: kaon-nucleon interactions revisited

The IfN interaction is of interest for nuclear, par-ticle and astrophysics . It is characterized by largerescattering effects between different channels andby the presence of the A(1405) resonance just be-low the RN threshold . From the theoretical point ofview one expects that chiral symmetry severely con-strains the interactions between the different chan-nels. However, because of such large rescattering ef-fects, for short unitarity corrections, pure meson-baryon chiral perturbation theory (CHPT) cannotbe applied. In particular, the resonance A(1405) canbe never reproduced in such a perturbative frame-work at any finite order because it is not perturba-tive in the chiral counting . Of course, one can cou-ple in an explicit A(1405) field, but in that case aconsistent power counting does not exist. As a con-sequence of that, a proper way of resummation ofthese strong unitarity corrections in the chiral expan-sion is necessary . One solution is to apply the chiralexpansion to generate an "effective potential" whichis then iterated in a Lippmann-Schwinger equationto calculate the whole S-matrix . Such ideas havebeen successfully pursued for ifN scattering basedon chiral Lagrangians and coupled channel pseudo-potentials in regulated Lippmann-Schwinger equa-tions, see [l, 2] . In these studies the nonperturba-tive nature of the strangeness S = -1 S-wave kaon-nucleon interaction was clearly established. However,from the theoretical point of view, the methods em-ployed in [l, 2] should further be improved . First,although chiral perturbation theory Lagrangians areused, a direct matching to the proper CHPT ampli-tudes is not done . Second, the results presented in[l, 2] show a strong sensitivity to the cut-off or reg-ulator masses . This can be avoided e.g . by employingsubtracted dispersion relations, with the added ad-vantage that the subtraction constants can even betaken at some unphysical points, where they can beconstrained by chiral symmetry. Third, the explicitinclusion of resonance fields in these schemes is not atall obvious . This becomes of importance if one wantsto decide whether a resonance is simply generatedby the strong meson-baryon dynamics or also has a"preexisting" (quark model) component . We presenthere a general and alternative scheme to that of in-troducing a potential in order to still apply chiralLagrangians to those situations where the perturba-tive chiral expansion fails because of the strong self-interactions between the relevant degrees of freedom .Note that these strong interactions can even gener-ate poles (e .g . bound states) in the S-matrix as ithappens e.g . in some channels of the IAN, nucleon-nucleon and even of the meson-meson systems. Theapproach is based on coupled channel subtracted dis-persion relations and on matching the general ex-pression for the pertinent partial wave amplitudesto the results of any given CHPT calculation in a

Ulf-G. Meißner and J .A . Oller

well defined chiral power counting . By construction,our approach is fully relativistic and thus one neverhas to make recourse to any expansion in the in-verse of the baryon mass. The method is suited toinclude the contributions of explicit resonance fields,if desired. It is a natural extension and reformulationof our previous work on pion-nucleon scattering [3].Although our approach is more general, in ref.[4] wehave shown that even starting from the lowest ordertree-level amplitudes of the kaon-nucleon system,one can fairly well describe the threshold branchingratios and scattering data as well as the event distri-butions . Note that we have developed an improvedmethod for calculating these event distributions asshown below .We briefly outline the general scheme that can beapplied to any order in the chiral calculations . TheIfN states couple strongly to several channels . Tobe consistent with lowest order CHPT, where allthe baryons belonging to the same SU(3) multipletare degenerate, one should consider the -whole set ofstates : K-p, b' on, ir°Eo, 7r+E, 7r E+, 7roA, nA,77Eo , K+E , KOEO . Unitarity gives rise to a cut in theT-matrix of partial wave amplitudes which is usuallycalled the unitarity or right-hand cut. Hence we canwrite down coupled channel dispersion relations forT-1(W)i7,

x f"0

-T-1(W)ij =--

Jijrai(so)+ s7r

so

ds' (S, -S)s)i- so) +T-1(W)_j,./ S(

where si is the value of the s = WZ variable (cmenergy squared) at the threshold of channel i and

7'-1 (W )i.9 indicates other contributions coming fromlocal and pole terms as well as crossed channel dy-namics . These extra terms will be taken directly fromCHPT after requiring the matching of our general re-sult to the CHPT expressions . For further details, see[4] . The calculated amplitudes T(W) depend on thevalues of the parameters mo and Fo (coming from

the lowest order CHPT amplitudes) and on the sub-

traction constants ai(y) . It is in fact sufficient to use

one single (average) value a(p) for all of them . We

first consider the set of natural values mo = 1 .15

GeV, Fo = 86.4 MeV and a(p) = -2, which we will

call set II in the following. In fig.l, the results of

our approach for this case for several K-p cross sec-

tions from threshold up to 250 MeV of the incoming

kaon three-momentum in the laboratory frame, kL,

are shown by the dashed lines . The values of the so-

called threshold ratios are: y = 2.05, Re = 0 .624 and

R,, = 0.264, quite close to the experimental values .

The case in which all the parameters mo, Fo and

a(y) are free is called set I. The parameters are fit-

ted to the scattering data below kL = 150 MeV and

to the threshold ratios . The values are: mo = 1286MeV, Fo = 74.1 MeV and a(y) = -2 .23, leadingto the threshold ratios, y = 2 .33, Rc = 0 .645, andR,, = 0.227 . It is remarkable that the values of theparameters mo, Fo and a(M) turn out to be in therange of the expected values from other sources ofphenomenology . On the other hand, although the re-production of the scattering data (as given by thesolid lines in fig.2) is very similar in quality to thatobtained with the previously fixed values for mo, Foand a(p), the ratios are better described.

Figure l: Scattering data in the low energy region .The solid and dashed lines refer to the parametersets I and II, respectively, as explained in the text .

We now consider the 7r-E+ event distribution in thevicinity of the A(1405). Typically this observable hasbeen calculated assuming that the process is domi-nated by the 7rE I = 0 system, so that it is pro-portional to the strong I = 0 TAE-+,F, S-wave am-plitude . However, we want to stress that this is anoversimplification since the threshold ofthe KN sys-tem is very close to 1 .4 GeV and one should considerfrom the beginning a coupled channel scheme . We dothis here following the approach given in ref. [5] forthe study of the J/T decays to a vector (0(1020) orw(782)) and to two pions or kaons . That problem isvery similar to the one here . In fig.2, we compare ourcalculated event distribution (shaded area) for set Iwith the experimental data from . The agreement israther satisfactory. Notice that this event distribu-tion is a result of the already fixed strong scatteringamplitudes .We have derived a general and systematic method toresum the right-hand cut contributions from a per-turbative (chiral) series . This method should be ap-plied whenever these contributions become far frombeing perturbative both in the low (or higher) en-ergy regimes, as for instance in the S-wave kaon-nucleon interactions for strangeness S = -1 as dis-cussed in detail here . The theory can be seen as areformulation in more general terms of the approachalready applied to study the meson-meson scatter-ing. Dispersion relations are used to perform the nec-

References :

Figure 2 : Event distribution in the region of theA(1405) for set I (shaded area) in comparison to thedata .

essary resummation of the chiral perturbation theoryamplitudes given at any order. These CHPT ampli-tudes are then incorporated in our general expres-sions for the partial wave amplitudes by requiringthe matching between both results in a well definedchiral power counting . Here, we have simply consid-ered the lowest order (tree level) CHPT approxima-tion as our starting point. A good description of thescattering data in the K-p, 7rF, and 7rA channels aswell as for the threshold branching ratios is obtained .In addition, we have given an improved theoreticalprescription to calculate the Ear event distributionsin the region of the A(1405) leading to a good re-production of the data . In the future, one should ex-tend these considerations . First, a second or thirdorder (relativistic) CHPT amplitude should be usedas input and higher partial waves should be included.Second, one should consider other strangeness chan-nels and also include explicit resonance fields (as it ispossible in this framework) . This is of particular in-terest for the question whether the A(1405) is a puremeson-baryon boundstate or has a small "preexist-ing" component.

[1]

N. Kaiser, P.B . Siegel and W. Weise, Nucl . Phys .A594 (1995) 325 .

[2]

E. Oset and A. Ramos, Nucl . Phys . A635 (1998)99 .

[3]

Ulf-G . Meißner and J.A . Oller, Nucl. Phys . A673(2000) 311.

[4] J .A . Oller and Ulf-G. Meißner, Phys . Lett . B(2001), in print, hep-ph/0011146 .

[5]

Ulf-G . Meißner andJ.A . Oller, Nucl . Phys . A679(2001) 671,hep-ph/0006263 .

1.

Introduction and formalism

In this work ref. [1] we develop an appropriate uni-tarization method to take into account the finalstate interaction corrections to the tree level ampli-tudes calculated from lowest order Chiral Perturba-tion Theory (XPT) [2] and from the inclusion of ex-plicit resonance fields in a chiral symmetric way[3] .We will work in the isospin limit considering the I7r7r)and IKIf) states, together with the p resonance, forthe I=1 channel. Furthermore, we also use a ma-trix notation, labeling pions with 1 and kaons with2. In the I=0 case we only have kaons (and the wand 0 resonances) . Starting from the unitarity of theS-matrix and the introduction of the electromag-netic meson form factor FMM, (s) defined as usual :

(y(q)ITIM(p)M I(pl))= ec,, (q)(p-p~)`'FMM'(s) (1)with q2 = s, e the modulus of the electron chargeand ey (q) the photon polarization vector, one arrivesto the expression :

FI(s)=[I+Q-1(s) .KI (s) .Q(s) .g'(s)J-iRI(s)

(2)

where Qij(s) = pi(s)Jij and KI(s) is the matrixcollecting the tree level scattering amplitudes#' be-tween definite 7rr and Iflf states . FI(s) is the col-umn matrix FI(s)i = Fir(s) ; RI(s) is a vector madeup by functions without any cut and gz(s) is thediagonal matrix given by the loop with two mesonpropagators (see ref.[1]) .The expression for the P-wave amplitudes TI(s) thatwe have used to go from eq.(1) to eq.(2) is providedby the NID method adapted to the chiral framework[4] .Loop physics is suppressed in the large Nr limit.Thus, in this limit FI(s) = RN, = Ft(s), whereFt(s) is the tree level form factor #2 . Thus one canwrite:

F"(s)

_

[I -t- Q-1(s) - KI(s) - Q(s) - 91 (3)] -1

[Ft(s) -f. SRI (s)]

(3)

where SRI(s) is a subleading polynomial in the largeNo counting O(Nj 1) . If we require that the vectorform factor of eq.(3) vanishes when s -+ oo as issuggested by experiment, we find that SRI (s) mustbe a constant . We fix the values of d= (parametersappearing in the gi functions [1]) and SRI=° (s) bymatching our results to those of the one loop XPT.*'Derived from lowest order XPTplus s-channel vector res-

onance exchange contributionscorresponding to the transitioni -+ j.#2The tree level form factors are also evaluated using the

lowest order XPT Lagrangian [2] plus the chiral resonanceones [3] .

Pion and kaon vector form factors

J. A. Oller, E. Oseta and J . Paloma'a Departamento de Ffsica Te6rica and IFIC, Valencia, Spain

On the other hand, the bare masses of the reso-nances are fixed by the requirement that the moduliof the scattering amplitudes have a maximum for

= MPesönänce We take SRI=1 (s) = 0 in order toconstraint further our approach although a best fitalso gives a value around zero with negligible influ-ence .

2 .

Results and conclusions

We can see a good agreement with experimental dataas shown in Fig.l . Furthermore, for low energies our

0.5

-0.5

-1 .5

160

120

100

so

60

40

20

b)

. .0 '

1 1000

,2000

500

-750 " 1000 "1250 1500w(uev)

Figure 1 : W is defined as Vs for s > 0 and as -vf--sfor s < 0. From left to right: a) 7r+ 7r- vector form fac-tor. b) 7r7r P-wave phase shifts . For the experimentaldata see ref.[1] .

amplitudes drive the correct resummation of the oneloop XPT vector form factors, being the agreementwith the two loop CHPT calculations much betterthan with the one loop results .References :[1] J. A. Oller, E. Oset and J. Palomar, 'Pion

and Kaon Vector Form Factors', FZJ-IKP(TH)-2000-10 . To be published in Phys . Rev. D.

[2]

J. Gasser and H. Leutwyler, Ann . Phys . NY 158

(1984) 142; J. Gasser and H. Leutwyler, Nucl .Phys . B250 (1985) 465, 517, 539.

[3] G . Ecker, J . Gasser, A. Pich and E. de Rafael,Nucl . Phys . B321 (1989) 311.

[4] J. A . Oller and E. Oset, Phys . Rev. D60 (1999)074023 .

1. Introduction

In ref.[1] we address the issue of giving a reliableand theoretically well sounded determination of thestrangeness-changing scalar form factors for the K7r,Kr7 and Kq' states up to around 2 GeV. These mag-nitudes are necessary in order to improve the QCDsum rule determination of the mass of the strangequark, which is a fundamentalparameter of the Stan-dard Model, as well as in the study of the leadingJ = 0 contribution to the T decay width.Our basic theoretical tools are Chiral PerturbationTheory (CHPT) [2], the chiral Lagrangians in thepresence of resonances[3] and the Chiral UnitaryApproach[4] .CHPT provides a systematic way to derive the QCDGreen functions as a power expansion in momentaand quark masses valid at low energies . Unfortu-nately, this framework breaks down for higher en-ergies and is only valid near threshold . The reasonis two fold : 1) The presence of explicit resonances,e.g . the p(770) and 2) the appearance of large uni-tary corrections, that is, contributions coming fromthe unitarity cut. The latter are particularly large inthe scalar sector, the one we are interested in .The first problem can be solved by constructing chi-ral symmetric effective field theories with explicitresonance fields[3]. The predictive power of theseLagrangians is largely increased by imposing QCDshort distance constraints which establish relationsamong the parameters of the theory and hence thenumber of free ones is reduced. In our study we willuse these Lagrangians to provide a prediction for thestrangeness-changing scalar form factors valid in thelarge N,, plus resonance saturation hypothesis . Wealso impose that the calculated tree level scalar formfactors vanish for s --* oo .The problem due to the large unitarity loop con-tributions, is handled by using the Chiral UnitaryApproach[4] . This approach establishes a rationaleto provide partial wave amplitudes that resum, toall orders in the chiral expansion, the right hand cutcontributions. The resulting final expressions are de-duced from the N/D method or directly by workingout a dispersion representation for the inverse of apartial wave amplitude. The input is provided bynext-to-leading order CHPT and by the resonancechiral Lagrangians, guaranteeing by construction themathcing with the chiral expansion at low energies .

2.

Results and discussion

The previous ingredients, namely, chiral Lagrangianswith or without resonances, the Chiral Unitary Ap-proach, together with the short distance constraints,

The K7r scalar form factor

M. Jamin', J. A. Oller and A. Pichb'Institut für Theoretische Physik, Universität Heidelberg, Germanyb Departamento de Fisica Te6rica and IFIC, Valencia, Spain

gave rise to a precise study of the S-wave K7r, Kr7and Kr7' scattering up to 2 GeV in ref.[5] . We fi-nally obtain the desired scalar form factors from thelatter partial wave amplitudes by using dispersionrelations .Unitarity of the S-matrix implies that ImFk (s) -~; ai(s)Fi(s)(t0(s))* where the scalar form factorsare Fk(s) _ -i-

2 (O~ä~`(üy~s)(0)~K~k) with01,2,3 = 7r, r/ and rl', in order . On the other hand,o-;(s) is the phase space and t° (s) the S-wave I=1/2partial wave amplitude[5] . Assuming that the formfactors vanish for s -+ oo and taking into accountthat the latter are analytical functions of s in thephysical sheet except for a cut from threshold up toinfinity due to unitarity, we can write the followingset of coupled integral equations for Fk(s) :

The previous equations are solved iteratively. Firstwe consider just the elastic K7r case which is morethan merely academic since the Kzr scattering is elas-tic up to rather high energies, 1.3 GeV or so . Thesolution to this case is the well known Omnes so-lution with the normalization at the origin fixed tothat of CHPT. We then implement the two chan-nel case by including the K77', since the Krl channelalthough lighter is almost negligible[5] . In fact, thetree level Kr7 form factor vanishes . First, we con-sider the previous Omnes solution and by makinguse of unitarity we obtain a first estimate of the Krfform factor . Then this result is introduced in eq.(1)and finally convergence is obtained after about 20iterations . We also notice that the final solution isindependent of the initial input since it is the samewhenever we cancel the initial K7f scalar or reverseits sign . Finally, we include the Kq channel whichonly gives rise to tiny corrections with respect thetwo channel case close to its threshold .References:

[2]

J. Gasser and H. Leutwyler, Nucl . Phys . B250(1985) 465, 517, 539.G . Ecker, J. Gasser, A. Pich and E. de Rafael,Nucl . Phys . B321 (1989) 311 .

[4] J. A. Oller, E. Oset and A. Ramos, Prog . Part .Nucl . Phys . 45, 157 (2000) ; J. A. Oller and U .-G . Meißner, hep-ph/0011146, to be published inPhys . Lett . B .

Fk (s) = E 1

ds~o-i(s')F'z(s')(t0 (s ')) * .

(1)i Jilth i

(s' - s - i 0+)

M. Jamin, J. A. Oller and A. Pich, `The K7rscalar form factor', in progress .

M. J'min, J . A . Oller and A. Pich, Nucl . Phys .B587, 331 (2000) .

J/,P -} Oww(KK) decays, chiral dynamics and OZI violation

The decays of the J/T into a 0 (or w) meson anda Goldstone boson pair (7r7r or KT) can be usedto investigate the dynamics of the interacting pseu-doscalars . These processes are considered to be me-diated by the corresponding scalar form factors ofthe pseudoscalar mesons if one considers the emit-ted vector meson as a spectator, see fig.1 . In ref.[1],we have developed a model for this process based onan effective Lagrangian . These reactions are rather

Figure 1 : Anatomy of the J/T decay into a 0 and aGoldstone boson pair (M = 7r or K) . S is the interpo-lating scalar field . The cross-shaded blob symbolizesthe final state interactions in the coupled 7r7r/K'Ksystem .

interesting since they are very sensitive to OZI vio-lation physics, in our scheme parameterized by theconstants ap and the low energy constants L4 andL6 of chiral perturbation theory (which vanish in thelarge N, limit where the OZI rule is exact) . The firstof these constants parameterizes the direct admix-ture of non-strange quarks to the scalar interpolat-ing field S for our model of the J/T decay with the0 playing the role of a spectator, see fig.l . The twolow energy constants enter the one loop descriptionof the pion and kaon scalar form factors. To describethese properly for the range of energies relevant here,we have combined information coming from next-to-leading order (one loop) chiral perturbation theory(CHPT) with the unitarity requirements which arevalid to all orders in the chiral expansion . In addition,we also have calculated for the first time the next-to-leading order CHPT kaon scalar form factors,for strange, ss, and non-strange, üu -I- id, scalar-isoscalar quark densities. The unitarity requirementswere imposed by using the strong I = 0 7r7r andK amplitudes derived in Ref.[2] . The amplitudesgiven in that paper not only describe accurately theS-wave I = 0 and I = 1 strong scattering data butalso have been used to successfully reproduce or evenpredict experimental data for a whole set of reac-tions, like e.g . -1y -+ 7r°7ro, 7r+7r- , K+K - , K°Ii-0and 7r°77 or 0 --) 'y7r° 7r° , y7r+7r- and -17<O77 . With thisinput, we have successfully described, from thresh-old up to around 1 .2 GeV, the event distribution ofthe 7r+7r- system in the J/T -~ 07r+7r- decay, seefig .2 . We have then predicted, in agreement with the

Ulf-G . Meißner, J .A . Oller

105

Figure 2: 7r+7r- event distribution in the J/1F ->

07r+7r- decay. The width of the bin is 25 MeV . Thesolid line corresponds to the best fit, the dashed anddot-dashed lines represent some of the theoreticaluncertainty, see [1] .

data from MARK-III, the event distribution of kaonsin the J/T -+ OK+K- reaction and the low energypart, where the S-wave dominates, of the event dis-tribution of 7r+7r- pairs in the J/T -+ w7r+7r- de-cay. Furthermore, the OZI violation parameter AO

comes out different from zero, AO = 0.17 f 0.06.This also holds for the low energy constants L4and L6 . We get 103 L4(1 .08 GeV) = 0 .44 ± 0 .11,103 Ls(1 .08 GeV) = -0.38±0.06 . While the value ofthe latter agrees with previous estimates, our resultfor L4 is sizeably larger in magnitude as most previ-ous estimations . However, it is compatible within er-rors with the quite constraint value derived by com-bining the information from O(p6) SU(2) and SU(3)CHPT . This offers another indication that the OZIrule does not account for the physics in the scalar0++ channel, as stressed e.g . in refs .[3, 4] . The schemeemployed here offers a unique approach to describethe scalar sector, which has been at the heart of manyinvestigations over the last decade .

References :

[1]

Ulf-G. Meißner and J.A . Oller, Nucl . Phys . A679(2001) 671, hep-ph/0005253 .

[2]

J. A. Oller andE. Oset, Nucl . Phys . A620 (1997)438; (E) Nucl . Phys . A652 (1999) 407.

[3] P. Geiger and N. Isgur, Phys . Rev. D47 (1993)5050 .

[4] S. Descotes, L. Girlanda and J. Stern, JHEP0001 (2000) 041.

1 .

Introduction and formalism

A precise determination of the strange quark mass,being one of the fundamental parameters in the Stan-dard Model (SM), is of paramount interest in severalareas of present day particle phenomenology beingthe topic of the work [1] . Until today two main meth-ods have been employed to achieve this task . QCDsum rules [2] and more recently also lattice QCD .The most recent unquenched lattice results[3] indi-cate a 25% reduction with respect the quenched ones .In this way, the values of the former tend to clus-ter around m, (2 GeV) = 90 f 6 MeV while the upto now QCD sum rules analyses give m, (2 GeV) -119±15 MeV. As a result, an update of the QCDsum rules analyses incorporating the new advancesin hadron physics given by the so called Chiral Uni-tary Approach[4] is mandatory .We consider the two-point function jy(g2) -i fdx e Tgx(0IT {j(x)j (0)t } 10), where in our case j(x)is the divergence of the vector current j(x) =&'(s'YN,u)(x)=i(m, - mu)(su)(x).After taking two derivatives of @(q2),

'F"(q2) van-ishes for large q2 and one can write a dispersion re-lation without subtractions,

"(q 2 ) = 2

00f ds (s - q2(-

i0+)s

The strange quark mass from QCD scalar sum rules

where p(s) is the spectral function of T(s), p(s)1ImT(s -+- i 0+).It is further convenient to apply a Borel transfor-mation to eq.(1) to suppress contributions comingfrom higher excited states . The left-hand side of theformer equation can be calculated within QCD whilethe right-hand side, under the assumption of duality,can be calculated from hadron physics .Nevertheless, the phenomenological spectral functionpph (s) is only known from threshold up to some en-ergy so . Above this value, one can also use the per-turbative expression pth (s) for the right-hand side forlarge enough values of so . Then the central equationof our sum-rule analysis is :

s0

00

U

th (u)=f ds e-s1upph (s)+f ds e -'1upth (s) .0

50

The theoretical two-point function is evaluated byusing the operator product expansion where theBorel transform f(u) can be expanded in powers of1/u as :

~(u)=(m,-mu)2+0(4d)+ T(u) I+Tü2

u) +11,us

u) -I-

By far, the most important contribution just comesfrom the pure perturbative result TO (u) with the rest

M. Jamin', J. A. Oller and A. Pichb'Institut für Theoretische Physik, Universität Heidelberg, Germanyb Departamento de Fisica Te6rica and IFIC, Valencia, Spain

106

of terms largely suppressed by powers of quantitiesof order ms over large scales of order 4 GeV2 .The phenomenological spectral function is given bythe modulus squared of the strangeness-changingscalar form factor[5] sum over the channels with theappropriate quantum numbers (in practice K7r, Kqand Krf) times phase space.

2 .

Results and discussion

Applying the previous scheme for three different val-ues of AQCD with three flavours, one obtains a verystable determination of m, with a very long plateaustarting at 2 GeV and extending up to 4 GeV, seeFig. l for m, (1 GeV) . Running to 2 GeV, we obtain :

References:

emen (G.V) et mu.t MV. .77 .5l0. FuN NWIte .09WdMntSR.

e~T3

1-M840YV81i4Y.:

.dar u.hu +x . .. .. .. .

.

. ..... . . . . .. . . .. . . .... . ..... . . .

...... . .....~. . . . ..... .,.

-. .. . .~: .

Figure 1 : Central values of m, (1 GeV) for three val-ues of AQCD =280, 380 and 480 MeV .

m, (2 GeV) = 112, 97 and 85 MeV for AQCD = 280,380 and 480 MeV, in order. An error analysis is stilllacking but these central values are in fair agreementwith the recent unquenched lattice determinations .

M. Jamin, J. A. Oller and A. Pich, `The strangequark mass from scalar sum rules', in progress .

[2] M. A . Shifm'n, A. I. Vainshtein and V. I. Za-kharov, Nucl . Phys . B147, 385, 448 (l979) .A. Ali Kahn et al . (CP-PACS Collaboration),hep-lat/0010078 ; D. Pleiter et al . (QCDSFand UKQCD Collaboration), hep-lat/0010063 .See also S . Narison, hep-ph/9911454 and H.Leutwyler, hep-ph/0011049 .

[4] J. A. Oller, E. Oset and A. Ramos, Prog .Part . Nucl . Phys . 45, 157 (2000) and referencestherein.M . Jamin, J. A. Oller and A. Pich, `The Kirscalar form factors', in progress . See also theseannual reports.

Chiral SU(3) low energy constants from 7r7r and 7rK scattering

The pseudoscalar octet of pions, kaons and the 77 maybe viewed as the Goldstone bosons of the sponta-neously broken approximate symmetry of the QCDLagrangian whose interactions may be described bySU(3) chiral perturbation theory [1] . The 7r7r and 7rKscattering amplitudes have been computed in thisframework sometime ago, see, ref. [2] . As chiral per-turbation theory is a non-renormalizable theory, itinvolves additional low energy constants (LECs) thathave to be introduced at each order of the momen-tum expansion. These constants are not determinedby chiral symmetry only, but have to be fixed fromexperimental values . As pointed out elsewhere [3],the most suitable region to match chiral quantities toexperimental values is some unphysical region insidethe Mandelstam triangle of the process under con-sideration . Dispersion relations are the suitable toolto analytically continue the available experimentalinformation to unphysical regions. Since 7r7r and 7rKscattering at low energies are governed by the S- andP-waves, it is justifiable to neglect the higher partialwaves (l >_ 2) in the dispersive framework .The structure of the 7rK amplitudes is best revealedby considering the 7rK amplitudes T' (s, t, u) whichare even and odd under the interchange of s andu, respectively . In the chiral framework up to or-der O(q6) these amplitudes can be written in termsof three functions of one variable whose absorptiveparts are related to those of the S- and P-waves,e.g .

T+ (s, t, u) = Zö (s) -{- Zö (u) + Zt (t)

+(t - s +A2

)Zi (u) + (t - u +02

)Z1 (s) .

In field theory the scattering amplitudes T+ and T-verify fixed-t dispersion relations, under conventionalassumptions regarding the high energy behaviour,the former with two subtractions and latter withnone . In practice, we have found that in order tomeet the requirements of matching the chiral expan-sion with the axiomatic representation, dispersion re-lations with two subtractions for T- as well proveto be convenient [4] . By using hyperbolic dispersionrelations the unknown subtraction constants can beexpressed in terms of the scattering lengths aö andso ,e.g .

T+(s, t, u) = 87r(m+M)aö + S+ + L+(t)

+U+(t) + ~ /'d2'[S

/s2s + s,

u2

u] As (s', t),

where S+, L+(t) and U+(t) are integrals over theabsorptive parts of T+(s, t, u) .Writing the Zt in a dispersive representation, onecan demonstrate in the S- and P-wave approxima-tion the equivalence of the structure of the dispersive

*Centre for Theoretical Studies, Indian Instituteof Science,560 012 Bangalore, India

P. Büttiker and B . Ananthanarayan*

107

representation to that of the chiral result . This allowsus to match the two representations in the low energydomain .To saturate the dispersion relations we use a simpleK-matrix approach providing the first estimates forcertain combinations of the low energy constants ofSU(3),e.g .

4L2 -I- L3

=

0.0016)

which has to be compared with [5]

4L2 + L3

=

0.0019 ± 0.0013.

To obtain predictions for further combinations of lowenergy constants, ?rir scattering can be treated in asimilar way. Using the available phase shift analyseswe find

to be compared with [5]

Although most of the estimates are in reasonableagreement with previous determinations, the devi-ations of some of our predictions emphasize the needof a more detailed analysis of the 7rK partial wavesand the importance of the contributions of the higherpartial waves. Work on that is in progress .

References :

[1] J. Gasser and H. Leutwyler, Nucl . Phys . B250(1985) 465.

[2]

V. Bernard, N. Kaiser and U.G . Meißner, Nucl .Phys . B357 (1991) 129 .

[3] P. Büttiker and U. Meißner, Nucl . Phys . A668(2000) 97, [hep-ph/9908247] .

[4] B . Ananthanarayan and P. Biittiker, [hep-ph/0012023], to be published in Eur . Phys . J . C

[5] J. Bijnens, G. Ecker and J. Gasser, [hep-ph/9411232] .

Lz = 0.00163,2Li + L3 = -0.0023,2L4 + L5r = -0.00156,

Lr2 = 'O .00135± 0.0003,2Li + L3 = -0.0027f 0.0012,2L' + Ls = 0 .0008 f 0.0009.

14

Correlating s- and t-channel form factors by dispersion relations

The GAMS and the BNL collaborations have pro-vided experimental results on the two-meson interactionvia the pion-proton reaction which has been claimed toinvalidate the interpretation of the fo(980) resonanceas a KK-molecule [1] . Since the Jiilich model gener-ates the fo(980) in such a way, we examined whetherthere is still sufficient attraction in the KK-channel toform a molecule, if we no longer use empirical cou-pling constants and form factors for the t-channel-interaction . We eliminate the need for empirical t-channel form factors by using the dispersion relation(1) to continue the microscopically calculated form fac-tor from the s-channel to the t-channel . Here r(iA 2 )is limt-, ig2 r(t)(t - iA2)/A2 with r(t) the microscopicform factor and A the cutoff in the empirical part of thes-channel form factor .

r(t)

-

n4A+t2 (A2R(r(iA2)) +ts(T(iA2))) (1)1 fcut

dt'7r

t

9t (r(9))

Figure 1 : Real part of the microscopic form factor atthe p7r7r- and pKK-vertices . Ticks: microscopically cal-culated values . Lines: Continuation to the t-channel(s-channel) .

The microscopic form factor for the s-channel is cal-culated by using the non-pole part of the ir7r-interactionto dress the p7r,7r-vertex, which by itself contains an em-pirical form factor to mimic theQCD part of the interac-tion. Figures 1 and 2 show the results of the microscopiccalculation for the p7r7r- and the pKK-form factors ascrosses and continuations to the t-channel as lines, in thecase that there is no coupling between the 7r7r- and theKK-channel. The plots show that the behavior of theform factor is dominated by the form factor introducedto take care of the QCD part of the interaction.Computing the phaseshifts and inelasticities dis-played in Figure 3, we also include the selfenergy forthe p in the t-channel, which we derive by dispersion re-lation from the s-channel . Up to a certain energy, wherefurther resonances need to be included, the results agreewell with the old data .

108

F. Sassen, S. Krewald, and J. Speth

250

200

150w

100

50

0.25

0.2

0.15

0.05

400350300250

w 200160100500L0

0

2000 -1000 0 1000 2000 3000 4000 5000+1)"2 ,0' In MoV

Figure 2: Imaginary part of the microscopic form factorat the p7r7r- and pKK-vertices . Ticks: microscopicallycalculated values . Lines: Continuation to the t-channel(s-channel) .

1 .0,J.O

1.0, J.0

CalculationProtopoPeacu t--+--+

Froggall x

1 .11

0.90.80.7

e 0.60.60.40.30.20.1

200 400 600 8001000120014001600

400

600

800 1000 1200 1400 1600Em� in MeV

Em � in MeV

1 .1, J.1

1.1, J.11.11

0.90.80.70.80.60.40.30 `+-rW~

i

0.2 1

,0

200 400 800 201000120014001600

400

600

BW 1000 1200 1400 1600E-In MeV

Eva, In MeV

References

a

Figure 3: Phase shifts and inelasticities in the J = O,I =0 and J = 1,I = 1 channel for our model including thep and the fo(1370) as exchange mesons . Data : [2, 3] .Lines: Theory

We find that the attraction in KK-channel is rela-tively weak, but sufficient to generate the fo(980) res-onance . The onset of the fo(1370) resonance is neededto generate a detailed agreement with the experimentalphase shifts . Till now no genuine fo(980) is needed inthe model.

[1]

Yu.D. Prokoshkin, Phys . At . Nucl 62 (1999) 356.

[2] S .D . Protopopescu et al ., Phys.Rev . D 7 (1973)1279 .

[3] C .D . Froggatt, J.L . Petersen, Nucl . Phys . B 129(1977) 89 .

On the Possibility of Observation of ao - fo Mixing in the pn -+ dao Reaction

The origin of the lightest, virtually mass-degenerate,scalar mesons ao(980) (1-0++) and fo(980) (0+0++)is one of the most important problems of hadronphysics. Different assumptions exist about the struc-ture of these mesons, from the standart qq states [1]to the 4-quark configurations [2] and and the light-est scalar mesons as "minions" in the Gribov con-finement model [3] . The problem of the structure ofao and fo mesons is closely related to the problemof ao - fo mixing . If the ao and fo mesons haveclose structures, then the mixing with violation ofisospin conservation could be large . Along with thedirect aoo -4 fo transition due to isospin violation inthe quark sector , these mesons can mix due to theisospin-violating interaction in the decay channels .It is convenient to examine ao - fo mixing in thereaction of production of neutral ao meson:

a'(pn -+ dao) oc Q3/ 2 ,

pn -3 dao.

(1)Note that the forward-backward asymmetry in thereaction (1) is absent if isospin is conserved . Anisovector ao meson can be produced near the thresh-old of the reaction (1) only in the p-wave with respectto the deuteron . At the same time if isoscalar fo isproduced in the reaction

pn -4 dfo,

(2)the final orbital angular momentum of the dfo sys-tem may be zero . This conclusion follows from theisospin, parity and total angular momentum conser-vation laws . Thus if isospin is conserved, the reac-tions (1) and (2) should have different energy andangular dependences . In particular, for the near-threshold production of stable mesons, one has

a-(pn -3 dfo) oc Q1/ 2 ,

(3)

where Q =V- ynd - fh is energy release in therespective reaction .Let us assume, that the fo -} ao transition can pro-ceed without isospin conservation . Then, the ao me-son in the reaction (1) can be produced in the s wavewith respect to the deuteron . Therefore, the p-waveamplitude of the main process (1) interferences withthe 8-wave amplitude of the isospin-violating processpn -' dfo -+ dao. Due to this interference, an asym-metry arises in the forward-backward escape of theao meson in the reaction (1), which is defined as

ir+--o'-

7:k = da

(4)

where 0 is the polar CM angle of aö-meson escape .We consider, that the ao - fo transition vertex Aafis the sum of main three terms shown in Fig. 1,Aaf = Adir+A �,i+ArtrR . The first term corresponds

A.Kudryavtsev a, V.Tarasov',

109

to direct transition from ao -+ fo at quark level . Weestimated vertex A�,, by direct calculation of dia-gramm in Fig.lb. The A,,, vertex corresponding tothe 7ro -71-transition in this diagramm is known fromthe analysis of the reaction 77 --> 37ro . The mechanismof external mixing due to the IiIf-channel is shownin Fig lc . This effect was discussed recently in ref .[4] . In our calculation we took into account only thecontributions from external mixing due to 7rrl andKK channels .We suggest to measure asymmetry A (4) looking forthe decay channel into rl7r . The lower limit of themass interval of the Iron-system is an important fac-tor for estimating asymmetry . The differential crosssection for the reaction pn -+ d7roq can be writttenas

TO =N ,~Q+m IM12kdm,

(5)mmin

where mmin = Yn - C(I'o/2), C is a variable pa-rameter. The calculations of asymmetry A (4) wereperformed at C = 1 and C = 2. The energy releasewas taken to be within f10MeV around threshold.The resulting asymmetry in the near-threshold re-gion was found to be large ( about 10-15 %), whichenables us to believe, that it can be experimentallyobserved . The more detailed version of this paper ispresented in ref.[5] .

b)

c)

Fig. 1: Different types of interactions resulting in the

aö - fo mixing.

a)

fo

a,-,fo

~tüO

a°

f°

``-If "~

aö

'also at : Inst . of Theoretical and Experimental Physics,117258, B.Cheremushkinskaya 25, Moscow, Russia

References :[1] N.A.Tomquist, Phys. Rev. Lett.49,624 (1982)[2] N.N.Achasov and G.N.Shestakov, Usp. Fiz. Nauk

161, 53 (1991) [Sov.Phys.Usp.34,471 (1991)].[3] V.N.Gribov, et all., Phys.Lett.B 319,291 (1993) .[4] B .Kerbikov and F.Tabakin, nucl-th/0006017, 2000 .[5] A.Kudryavtsev and V.Tarasov . JETP Letters,

72,410 (2000) .

On the origin of the short-range repulsion in the KN system

A few years ago the Jiilich group has presented ameson-exchange model for the K+N system [l, 2] .This model includes single boson exchanges (o-, p,w) together with contributions from higher-order di-agrams involving N, A, K and K* intermediatestates . It turned out that the KN experiments canonly be described with this model if one increasesthe value of the Kh'w coupling constant about60 % above the value that follows from the SU(3)(quark flavor) symmetry. This certainly surprisingresult was interpreted as a strong indication that w-exchange, as treated in this meson-exchange model,is an effective contribution that parametrizes be-sides the "physical" w-exchange also further shorter-ranged mesonic contributions or genuine quark-gluoneffects or both [1] . Indeed, the results presented inRef. [1] indicated clearly that the required additionalcontributions must be much shorter ranged than thew exchange . This was shown by a model analysiswhere the coupling constants of the w meson (gKKw,9NNw) were kept at their SU(3) symmetry valuesand an additional phenomological (extremely short-ranged) repulsive contribution, a "arep" with a massof about 1 .2 GeV, was introduced [l, 2] .However, it is still an open question whether this con-tribution, which was introduced phenomenologicallyin Refs . [l, 2], can be understood dynamically. Inour study we want to address the question whetherquark-gluon dynamics can provide sufficient addi-tional repulsion as required by the data . Recently,one of us (D .H .) has derived the contribution of thespin-spin part of the one-gluon exchange to the cen-tral part of the KN interaction [3]. With the centralpart one can already get a quantitative insight intothe quark-gluon effects on the KN S-waves becausethe other components of the one-gluon exchange suchas the Coulomb piece are expected to yield only mi-nor contribution here [4] .Our results for the Sol and Sll KN partial waves (weuse the standard notation L21,2J) are presented inFig. 1 . The solid curves show the result for the orig-inal Jülich model I [2] . (Note that we have switchedoff the contributions from higher-order (box) dia-grams for simplicity reasons. Those box diagramsinfluence mostly the higher partial waves, anyway[1]) . The dashed curves represent the results wherethe phenomenological repulsive short-range contri-bution, a'rep, is switched off. It is evident that theO"rep plays an important role for the S-waves. Thedash-dotted curves are obtained when the contri-butions from the one-gluon exchange potential areadded to the Jiilich model instead of the arep . Wecan see that for the isospin I=1 channel the con-tribution from the quark-gluon potential is indeedalmost large enough to explain the phenomologicalrepulsion needed in the Rilich KN model . Its contri-bution in the I=0 channel is, however, significantly

D. Hadjimichefl, J. Haidenbauer, and G. Krein2

smaller and therefore not sufficiant to describe themissing repulsion .We are presently working on the derivation ofthe spin-orbit interaction resulting from the quark-model. This will allow us to investigate also thebehaviour of the higher partial waves of the KNsystem . Furthermore, we want to take into accountthe Coulomb piece of the one-gluon exchange whichyields a contribution to the central part of the KNinteraction . It will be interesting to see whether thisadditional piece can modify the results for the S-waves qualitatively.

Fig. 1 : S-wave KN phase shifts for the isospin zero(top) and isospin one (bottom) channels . Thesolid line is the result of the Jillich model I[2]. The dashed curves show the results with-out the contributions of the phenomenologi-cal repulsive o-,,p exchange . The dash-dottedcurves are the results where the contributionsfrom the one-gluon exchange are included in-stead of the repulsive a,,p .

References :[1] R. Büttgen et al ., Nucl . Phys . A 506, 586 (1990)-[2] M . Hoffmann et al ., Nucl . Phys . A 593, 341

(1995) .[3] D. Hadjimichef, hep-ph/0006330 .[4] D . Hadjimichef et al ., in preparation.Departamento de Fisica, Universidade Federal de

Pelotas, Pelotas, BrazilInstituto de Fisica Te6rica, Universidade Estadual

Paulista, SSo Paulo, Brazil

Direct CP violation can be measured in the decay--> Air -> p7r7r . To extract the CP violating phase,

one has to know the strong ATr S- and P-wave phaseshifts at the mass of the cascade, denoted So andSl , respectively. While earlier calculations were in-conclusive on the value of S0, a leading order heavybaryon chiral perturbation theory (HBCHPT) anal-ysis led to a vanishing S-wave phase shift and cor-rections including excited E intermediate states wereshown to give a bound of So - 0.50 . Relativistic treelevel calculations have also been performed, leadingto a somewhat larger band of values for S0 , but stilllJo l < 2' . A more recent calculation using also di-mension two operators [1] with the correspondinglow-energy constants fixed from kaon-nucleon scat-tering gave the range -3.00 <_ So <_ +0.40 . In thatpaper, the effect of channel coupling was also inves-tigated, based on the observation that in SU(3), theAir state is coupled to the E7r, NIf, Erg and 'EKstates with strangeness S = -1 and isospin I = 1. AK-matrix approach was used to calculate the chan-nel coupling effects and a surprisingly large So - -7°was found. The authors of ref.[1] have been careful topoint out that more refined coupled channel calcu-lations based on chiral perturbation theory (CHPT)are necessary to further clarify this surprising result .This was done in ref. [21, using a novel relativistic chi-ral unitary approach based on coupled channels [3] .Dispersion relations are used to perform the neces-sary resummation of the lowest order relativistic chi-ral Lagrangian . Within this framework, the S-wavekaon-nucleon interactions for strangeness S = -1were studied and a good description ofthe data in theK-p, 7rE and 7rA channels (cross sections, thresholdratios, mass distribution in the region of the A(1405))was obtained . It is straightforward to project out theA7r -> Air amplitude from our coupled channel solu-tions and extract in a parameter-free manner thecorresponding S-wave phase shift.Using the lowest order relativistic (tree level) CHPTamplitudes for Goldstone boson-baryon scattering,OiBa -+ OjBb, as input, one obtains a very good de-scription of the scattering data in the KN system,in terms of three parameters . These are the baryonoctet mass in the chiral limit, mo, the chiral limitvalue of the three-flavor meson decay constant, Fo,and a subtraction constant a(y) . In ref. [31, two sets ofparameters were considered, set I describing the bestfit and set II using the so-called natural values . Thepertinent numbers are for set I: mo = 1 .286 GeV,F'0 = 74 .1 MeV a(p) = -2.23, and for set II_ mo =1.151 GeV, F0 = 86 .4 MeV, a(y) = -2 at the scaleF1 = 630 MeV. Of course, physical observables arescale-independent . It is now straightforward to ex-tract the A7r phase shift as shown in fig . 1 by thesolid line (set I) and the dashed line (set II). Thecorresponding phases at the mass of the SO and the

The S-wave Air phase shift at the mass of the E

Ulf-G . Meißner and J .A . Oller

are:set I : So(m-Eo) = 0 .10° , So (m_-) = 0.16° ,set II : So(rn_o) = 0 .92° ,So(m_-) = 1.11 0 ,

consistent with earlier CHPT findings . We shouldstress that set I gives the better fit in the KN sectorand should be preferred .

Figure 1: The A7r phase shift in degrees versus thecm energy (see text for explanations) .

It is important to understand the large result ob-tained in the K-matrix formalism [1] . The K-matrixapproach is one particular approximation to ourscheme in that ones simplifies the scalar meson-baryon loop function as g(s)i = -(iqi)/(87rW) . Inorder to see the importance of keeping the wholeg(s)i function, compare the dashed and dash-dottedlines in fig.l . The latter is obtained for set II by mak-ing by using the K-matrix approximation for g(s)i .The differences are huge and for the second case theresults are similar to the findings of ref.[1] . Conse-quently, the large and negative value for So = -7°of ref.[1] can be ruled out. Furthermore, the phasesare sensitive to Fo and mo . We conclude from ourapproach that indeed So is narrowly bounded,

00 <S0<1.10 ,

( 1)

and that the large value found in the K-matrix ap-proach should not be used .

References :

J. Tandean, A.W. Thomas and G . Valencia,subm . to Phys . Rev. D, hep-ph/0011214 .

[2] J.A . Oller and Ulf-G. Meißner, subm. to Phys .Rev . D, hep-ph/00112 93 .

[3] J .A . Oller and Ulf-G. Meißner, Phys . Lett . B(2001), in print, hep-ph/0011146 .

Recently we developed a model for the reactionspp -+ ppw and pp -} ppo within the conventionalmeson-exchange picture [l, 2] . In this model mesonproduction is described by the mechanisms, namelythe nucleonic current and the 7rpV (V = w, 0) me-son exchange current, cf. Ref. [1] for details . We em-ployed this model for a combined analysis of close-to-threshold 0 and w production data with specialemphasis on the apparent violation of the Okubo-Zweig-Iizuka (OZI) rule reported by the DISTO col-laboration [3] . It turned out that the data do not re-quire a large NNO coupling constant [2]. Indeed therange of values for 9NNO extracted from this analy-sis was found to be compatible with the OZI value- which might be interpreted as an indication thatthere is no need for introducing an ss componentinto the nucleon in order to understand those data .Now we have applied this model to the reactionspn -} dw and pn -4 d¢ [4] . We would like to empha-size that all our model parameters are already fixedfrom our previous study [2], where they were con-strained by requiring a consistent description of thereactions pp -} ppw andpp -+ ppo. Therefore, we areable to provide genuine predictions for observablesof the reactions pn -+ dw and pn -+ do. However,the lack of a more complete set of data for the ppinduced reactions prevented us from determining aunique parameter set in Ref. [2]. Rather, we arrivedat four different model solutions that all provide acomparably good description of the pp -+ ppw andpp -+ ppo data, cf. Ref. [2]. It will be interesting tosee whether these models lead to distinctly differentresults for the reactions pn -+ dw and pn -4 do.Predictions for the reaction pn -+ do are shown inFig. 1 (for parameter set 1 of given in Table II ofRef. [2]) where we also indicate the contributions ofthe nucleonic and the meson-exchange currents . Ev-idently, the reaction pn -+ do is strongly dominatedby the meson exchange current. The relative magni-tude of the contribution from the nucleonic currentis even smaller than in case of pp -+ ppo [2] . Like forpp -> ppo, there is a destructive interference betweenthe nucleonic current and the meson exchange cur-rent which, however, is now much less pronounced .The features found for the other model parametersets are practically the same. Corresponding resultscan be found in Ref. [4].Fig . 1 contains also our predictions for the reac-tion pn -+ dw. Also here we observe that the me-son exchange current is the dominant productionmechanism . Its relative importance is likewise in-creased compared to pp -+ ppw . However, for the caseof w production the nucleonic current is still largeenough to introduce sizable interference effects. Theextent of these interferences depends significantly onthe specific model parameters . Consequently, we ob-tain a much stronger variation of the predicted cross

The reactions pn -~ dw and pn -+ do near thresholdK. Nakayamm', J. Haidenbauer, and J. Speth

sections for pn -+ dw than for pn -+ do . Indeedthe results vary by a factor of roughly 3 [4] . Thestronger variations in the w production cross sectionhave also consequences for the cross section ratioRol,, _ O'pn-+d¢/O'pn-+dw relevant for the compari-son with the prediction that follows from the naiveOZI rule [5] . These aspects are discussed in detail inRef. [4] .

10'

1e

10-'

10-' 0 10 20 30 40 50 60 70 80 90 100Q [MeV]

Fig . l: Total cross section for the reactions pn -4 do(top) and pn -3 dw (bottom) as predicted bythe model set 1 as a function of the excessenergy Q. The solid line is the result of thefull model. The dashed (dash-dotted) curvesshow the contributions of the nucleonic cur-rent (meson exchange current) alone .

References:[1] K. Nakayama, A. Szczurek, C . Hanhart, J .

Haidenbauer, and J. Speth, Phys. Rev. C57,1580 (1998) .

[2] K. Nakayama, J.W. Durso, J . Haidenbauer, C .Hanhart, and J. Speth, Phys . Rev. C60, 055209(1999) .

[3] F. Balestra et al ., Phys . Rev. Lett . 81, 4572(1998) .

[4] K . Nakayama, J . Haidenbauer, and J . Speth,Phys . Rev. C63, 015201 (200l) .

[5] H.J . Lipkin, Phys . Lett . 60B, 371 (l976) .

1 Department of Physics and Astronomy, Universityof Georgia, Athens, GA 30602, USA

A recent measurement of the reactions pp --+ pAK+and pp --) pE'K+ close to their thresholds revealeda strong suppression of the Eo production . Its crosssection turned out to be a factor of 30 smaller thenthat for the A production [1] . In contrast to thatthe Eo production at higher energies is only about afactor of 3 smaller.In a previous work [2] we argued that this large crosssection ratio can be possibly explained by an inter-ference between the two basic mechanisms of thesereactions, namely K and 7r exchanges (Fig . 1) .

~, K

The reaction pp -+ NEK close to threshold

A.M . Gasparian', J. Haidenbauer, C. Hanhartz , L. Kondratyuk', and J. Speth

Fig. 1 : Contributions to the pp -+ pYK amplitude .

This interference is unimportant for the A produc-tion, since it is dominated by the K exchange [2] .However, for the reaction pp -4 pEOK+ the two con-tributions are of the same order and they can add upconstructively or nearly cancel each other. Indeed,the results presented in Ref. [2] suggest that onlywith a destructive interference (we will note this casewith "K - 7r" in the following) one is able to achievea cross section ratio that is close to the experimentalone, whereas a constructive interference ("K -1- 7r")unavoidably yields much too small ratios .Of course, the interference pattern has also conse-quences for the other E production channels . Thus,it is interesting to look at the corresponding predic-tions. E.g ., for the reaction pp -+ nE+K+ the in-terference pattern is just the opposite as for pp -+PE OK+, cf. Fig. 2. Specifically, for the "K - 7r"case favoured by the experimental A/Eo produc-tion ratio our calculation yields a cross section forpp -+ nE+K+ that is about 3 times larger then theone for pp -4 pEOK+ . Such a ratio is in fair agree-ment with data at higher energies [3] . The otherchoice, "K + 7r", leads to a upp->nE+K+ that is afactor of about 3 smaller than O'pp-+pEOK+ - a resultwhich is rather difficult to reconcile with the presentknowledge about these reactions at higher energies .In case of the reaction pp -+ pE+Ko the inter-ference pattern turns out to be the same as forpp -4 PEOK+, cf . Fig. 2 . Here the cross section forpp -+ pE+Ko is about 3(6) times larger then the onefor pp --~ PEoK+ when choosing "K -h 7r" ("h' - 7r") .We should mention that the experimental evidenceat higher energies suggests a ratio of around 1 forthose channels .

1000

100

b 10

1000

100

References:

0

1000

100

10

pp-4ploK+

5 10 15excess energy [MeV]

0 5 10 15excess energy [MeV]

0 5 10 15excess energy [MeV]

Fig. 2 : Total cross section for the reactions pp -+ NEK.The data are from Ref. [1] .

Note that all curves in Fig. 2 are multiplied by acommon reduction factor of 0.3 [2] to compensate forISI effects [4] . Also we want to emphasize that thecorresponding results for the reaction pp -> pAK+(for "K + 7r" as well as "h' - 7r") are in agreementwith the experiment [2].'also at : Inst . of Theoretical and Experimental Physics,117258, B.Cheremushkinskaya 25, Moscow, Russia'Nuclear Theory Group and INT, Dept . of Physics, Uni-versity of Washington, Seattle, WA 98195-1560, USA

[1] S. Sewerin et al ., Phys . Rev. Lett . 83, 682 (1999) .[2] A.M . Gasparian et al., Phys . Lett. B 480, 273

(2000) .[3] J.M . Laget, Phys . Lett . B 259, 24 (1991) .[4] M. Batinic et al., Phys . Scripta 56, 321 (1997) .

N Y ~, K Y N

N Y Y NK 7c

P P P P

We have performed a microscopic calculation of thereaction pp -+ pp7l in the near-threshold region . Theproduction mechanisms which have been includedconsist ofrescatterings terms withM= p, 7r, rl, o- me-son exchanges (Fig.la) and the direct 77 production(Fig . 1b),

77-meson production in the reaction pp -+ pprlV. Barua, A.M. Gaspariana, A. Kudryavtseva, J. Haidenbauer, and J . Speth

p

p

Fig. 1: Diagrams for n production . (a) One-boson ex-change contribution (M = 7r, n, p, o) ; (b) directproduction

Since we are not far from threshold the outgoing par-ticles are assumed to be in S-waves. Effects of thefinal (FSI) and initial state interaction (ISI) betweenthe nucleons are taken into account via correspond-ing calculations of one loop diagrams in the finaland initial states, respectively. For the NN inter-action we utilize the Paris potential [1] and a ver-sion of the Bonn NN model (CCF of Ref. [2]) . Themain novelty of our calculation lies in the employ-ment of a realistic model for the MN -+ r7N tran-sition amplitudes . They are taken from a coupled-channel model of the rrN system developed in Jülich[3] . It contains explicitly the channels 7rN, pN, r7N,7rN* (1520), o"N, and rrA . This model yields a satis-factory description of the available 7rN phase shiftsand inelasticities from the rrN threshold up to ener-gies of about 1 .9 GeV as well as of the TrN -+ r7Nand rrN -4 pN transition cross sections . The formfactors appearing at the MNN vertices (in Fig. la)are assumed to be of monopole type . Correspond-ing vertex parameters (cutoff masses and couplingconstants) are taken over from the full Bonn NNpotential .Resulting total cross sections for the reaction pppprl are shown in Fig. 2. Obviously the predictionsare sensitive to the employed NN model. Also, wesee that the calculated energy dependence deviatessomewhat from the one shown by the experimentaldata. Most likely this is due to effects of the 77N-interaction in the final state [4, 5], which is - so far- not taken into account in our analysis . The maincontribution to the cross section comes from the p-exchange amplitude Mp as can be seen in Fig. 3.The contributions of rr and 77 are comparable (onlythe former is shown in Fig. 3), but M� is almostorthogonal to Mp , whereas M,7 contributes construc-tively . Due to a cancellation between the o--exchangeamplitude and the contribution of the direct produc-

tion term the calculated cross section is mainly de-termined by the p, 7r, and rl rescattering diagrams .At present we are working on the inclusion of higherpartial waves both for the NN- and for the qN-interaction. Then we are able to extend our inves-tigations to higher energies and to look at other ob-servables like differential cross sections and polariza-tions for which experimental data are already pub-lished or about to became available [6] .

F4

b

Fig. 2: Total cross section for the reaction pp -+ ppqcalculated with different potentials for the NNinteraction . The solid curve corresponds to theParis potential, the dotted one to the Bonn po-tential (CCF version) .

References :

0L0

5

2

5 10 15 20 25Q [Mev]

Fig. 3: Contributions of the different rescattering pro-cesses to the total cross section . The Paris po-tential is employed.

aalso at : Institute of Theoretical and Experimental Phy-sics, 117258, B.Cheremushkinskaya 25, Moscow, Russia

[1) M. Lacombe et al ., Phys. Rev,2] J. Haidenbauer, K . Holinde,Phys . Rev. C 48, 2190 (19931

[3] O. Krehl, Jülich-Report RU-36.92 (1999) ; O. Krehl et

al., Phys . Rev. C 62, 025207 (2000) .5 H. Calen et al ., Phys . Lett . B366, 39 (1996) .J. Smyrski et al ., Phys . Lett . B474 182 (2000) .~6] H. Calen et al ., nucl-ex/9811o03 (1998) ; J. Sm rskiet al ., Annual Report 1998, p. 39 .

C 21, 861 (1980) .and M.B . Johnson,

..71 p p p

-_ _ -o d

p p p

Pion-nucleon scattering to fourth order in chiral perturbation theory

Pion-nucleon scattering at low energies is one of themajor playgrounds to test our understanding of thespontaneous and explicit chiral symmetry breakingof QCD. It has already been investigated to third or-der in the chiral expansion in refs .[l, 2], raising somequestions about the convergence. In addition, acom-plete one-loop analysis must also include all fourthorder terms. Such an analysis was provided in ref.[3] .The complete one-loop amplitude for elastic pion-nucleon scattering in heavy baryon chiral perturba-tion theory contains 13 low-energy constants (LECs)plus one related to fixing the pion-nucleon couplingconstant through the Goldberger-Treiman discrep-ancy . Their values can be determined by fitting to thetwo S- and four P-wave partial wave amplitudes forthree different sets of available pion-nucleon phaseshifts in the physical region at low energies (typi-cally in the range of 40 to 100 MeV pion momentumin the laboratory frame) . We have performed twotypes of fits . In the first one, we fit four combinationsof the dimension two and four LECs, together withfive LECs from the third and five from the fourthorder. This means that the dimension two LECs aresubject to quark mass renormalizations from certainfourth order terms . Most fitted LECs are of "natu-ral" size . In the second approach, we fix the dimen-sion two LECs as determined from the third orderfit and determine the corresponding dimension fourLEC combinations separately. We have studied theconvergence of the chiral expansion by comparing thebest fits based on the second, third and fourth or-der representation of the scattering amplitudes . Thefourth order corrections are in general not large, butthey improve the description of most partial waves.This indicates convergence ofthe chiral expansion, asshown in table 1 for the S-wave scattering lengths,and in the fig . 1 for the phases .

Table 1: Convergence of the S-wave scatteringlengths for the three fits, see ref.[3] . O(q") meansthat all terms up-to-and-including order n are given.Units are 10 -2/MV .We can predict the phases at lowerand at higher en-ergies (see fig . 1), in particular the threshold param-eters (scattering lengths and effective ranges). Theresults are not very different from the third orderstudy in [2], but the description of the P-waves isimproved, in particular the scattering length in thedelta channel (P33) and the energy dependence of the

Nadia Fettes, Ulf-G . Meißner

small P-waves. The errors on the S-wave scatteringlengths are as in [2] since they are due to the dif-ferences in the partial wave analyses used as input .Our theoretical predictions are consistent with recentdeterminations from picnic hydrogen and deuterium(done at PSI) .

References:

50 100 150 200S31 q� [MeV]

S11 q, [MeV]

0

50 100 1so 200P33 q,[MeVI P31

q . [MeV]

-2

0 50 100 150 200 0 50 100 150 200P13 q.[MeVI P11 q,[MeV1

Figure 1 : Fits and Predictions for the EM98 phaseshifts as a function of q, . Fitted in each partial waveare the data between 41 and 97 MeV (filled circles) .For higher and lower energies, the phases are pre-dicted as shown by the solid/dashed/dotted lines tofourth, third and second order. The leading order re-sult free of LECs is shown by the dot-dashed lines .

The pion-nucleon sigma term (at zero momentumtransfer) can not be predicted without further inputsince at fourth order a new combination of LECsappears, that is not pinned down by the scatteringdata . Therefore, we have analyzed the sigma termat the Cheng-Dashen point. Using a family of sumrules which relate this quantity to threshold param-eters and known dispersive integrals, we find resultsconsistent with other determinations using the vari-ous partial wave analyses .

. 0

[1] M. Mojzis, Eur. Phys . J . C2 (1998) 181.[2] N. Fettes, Ulf-G. Meißner and S. Steininger,

Nucl . Phys . A640 (1998) 199.[3]

N. Fettes and Ulf-G. Meißner, Nucl . Phys . A676(2000) 311 .

O(q) O(q') d(q) d (q4)

fit 1 0 .0 0 .46 -1.00 -0 .96ao+ fit 2 0 .0 0 .24 0.49 0.45

fit 3 0 .0 1 .01 0.14 0.27fit 1 7 .90 7 .90 9.05 9.03

ao+ fit 2 7.90 7 .90 7.72 7.71fit 3 7 .90 7.90 8.70 8.67

Pion-nucleon scattering in an effective chiral field theory with explicit spin-3/2 fields

Pion-nucleon scattering is an important testingground for our understanding of the chiral dynamicsof QCD . It has been investigated to third and fourthorder in the chiral expansion, leading e.g . to pre-cise predictions for the threshold parameters . Thisapproach is based on an effective field theory withthe active degrees of freedom being the asymptoti-cally observable pion and nucleon fields . When go-ing to higher energies, the usefulness of the chiralexpansion is limited by the appearance of the nu-cleon resonances, the most prominent and importantof these being the 0(1232) with spin and isospin3/2. Its implications for hadronic and nuclear physicsare well established. Consequently, one would liketo have a consistent and systematic framework toinclude this important degree of freedom in baryonchiral perturbation theory, as first stressed by Jenk-ins and Manohar [1] and only recently formalized byHemmert, Holstein and Kambor [2]. Counting thenucleon-delta mass splitting as an additional smallparameter, one arrives at the so-called small scaleexpansion (which differs from the chiral expansionbecause the NA splitting does not vanish in the chi-ral limit) . We have constructed the one-loop ampli-tude for elastic pion-nucleon scattering based on aneffective field theory including pions, nucleons anddeltas to third order in the small scale expansion,(x(83 ), where e collects all small parameters (exter-nal momenta, the pion mass and the nucleon-deltamass splitting) [3] . We have constructed the per-tinent terms of the effective Lagrangian includingthe 1/m corrections. The amplitude contains alto-gether 14 low-energy constants from the nucleon, thenucleon-delta and the delta sector (if we count theleading 7rNA coupling constant g7rNo as a LEC) .The values of the LECs can be determined by fit-ting to the two S- and four P-wave amplitudes fordifferent sets of available pion-nucleon phase shiftsin the physical region at low energies . We have per-formed two types offits . In the first one, we fit to theMatsinos phase shifts in the range of 40 to 100 MeVpion momentum in the laboratory frame. This al-lows for a direct comparison with the results basedon the chiral expansion. We find that the third orderSSE results are clearly better than the ones of thethird order chiral expansion and only slightly worsethan the ones obtained at fourth order in the pion-nucleon EFT. Second, we have fitted to the Karl-sruhe phase shifts for pion lab momenta between 40and 200 MeV. This allows for a better study of theresonance region . In both cases, most fitted LECs areof "natural" size . We have studied the convergenceof the small scale expansion by comparing the bestfits based on the first (leaving the coupling constantg7rwo free), second and third order representationof the scattering amplitudes . The third order cor-rections are in general not large, but they improve

Nadia Fettes, Ulf-G. Meißner

the description of most partial waves. This indicatesconvergence of the small scale expansion for this pro-cess . As anticipated, the most important contribu-tions come from the tree (Born) graphs with interme-diate delta states . This allows to pin down the cou-pling constant gnNO fairly precisely. We can predictthe phases at lower and at higher energies, in . par-ticular the threshold parameters (scattering lengthsand effective ranges) . The results are not very dif-ferent from the third and fourth order studies basedon the chiral expansion, but the description of thescattering length and the energy dependence in thedelta channel are clearly improved, see fig .l . Whilethe convergence of the isovector S-wave scatteringlength is satisfactory to third order in the small scaleexpansion, for drawing a conclusion on the isoscalarS-wave scattering length a fourth order calculationis mandatory . We have also studied a-term .

25

"ö 20

15

0

'0-0.5

References :

50 100 150 200 0 50 100 150 200S31 q.[MeVI

S11 q., IMeVJ

0

-2

0 0

50

100

150

200

00

,50 , ,100 ' , , 150 , " ,200P33

q. [MeV]

P31 q � IMeVI

0

-0 .5

-1 .5

-2

0 50 100 150 200 0 50 100 150 200P13

q, [MeV]

P1 1

q .. [MeV]

Figure 1: Fits and predictions for the EM98 phaseshifts as a function of the pion lab momentum . Fit-ted in each partial wave are the data between 41 and97 MeV . For higher and lower energies, the phasesare predicted as shown by the solid lines . Dottedand dashed lines: Third and fourth order calculationbased on the chiral expansion .

E. Jenkins and AN. Manohar, Phys . Lett . B259(1991) 353.T.R . Hemmert, B.R . Holstein and J. Kambor,J. Phys . G: Nucl . Part . Phys . 24 (1998) 1831 .N . Fettes and Ulf-G. Meißner, Nucl . Phys . A679(2001) 629, hep-ph/0006299 .

Towards an understanding of isospin violation in pion-nucleon scattering

Pion-nucleon scattering (7rN) is one of the primereactions to test our understanding not only of thespontaneous and explicit chiral symmetry breakingQCD is supposed to undergo, but also ofisospin sym-metry violation . The pion-nucleon system is partic-ularly well suited for such an analysis, since chiralsymmetry breaking and isospin breaking appear atthe same chiral order.

The analysis of isospin violation in 7rN scatteringproceeds essentially in three steps. First, one ignoresall isospin breaking effects, i.e . one sets e = 0 andmu = Md . This is the approximation on which theanalysis in refs . [1, 2] was based. These papers com-prise the most detailed studies of pion-nucleon scat-tering in the framework of heavy-baryon chiral per-turbation theory . It is obvious that one needs a pre-cise description of the large isospin symmetric "back-ground" of the scattering amplitude in order to beable to pin down the small isospin violating effects .The quality of the results obtained in refs . [1, 2]makes us feel confident that we have a sufficientlyaccurate starting point.

.

In the second step, one should include the leadingisospin breaking terms encoded in the pion and nu-cleon mass differences. The mass splitting for thenucleons amounts to about 1 MeV, whereas thecharged- to neutral-pion mass difference is ofthe or-der of 5 MeV. To the accuracy we are working (thethird order in small momenta and charges) one hasto consider such effects. The strength of chiral per-turbation theory now lies in the fact that one canconsistently take into account only the effect fromthose isospin violating low-energy constants whichenter the particles' masses . This is the approxima-tion which we will consider here . In fact, in neutral-pion photoproduction off nucleons, to third order insmall momenta, this approximation leads to the onlyisospin breaking effect, which reveals itself in thelarge cusp effect at the secondary threshold (i .e . atthe 7r+n threshold in the case of yp -} 7rop) .

In a third step, one has to include all virtual pho-ton effects and directly fit to cross section data topin down the novel electromagnetic low-energy con-stants .We have performed an analysis of isospin breakingeffects in pion-nucleon scattering due to the lightquark mass difference and the dominant virtual-photon effects, corresponding to step two mentionedbefore, see ref.[3] . The pertinent results of that studyare:

(i) We have taken into account all operators re-lated to strong isospin breaking and the elec-tromagnetic ones that lead to the pion and nu-cleon mass differences. Stated differently, the

Nadia Fettes, Ulf-G. Meißner

finite parts of some of the virtual-photon op-erators contributing at this order have beenset to zero . This allows in particular to isolatethe contribution of the strong isospin breakingdimension-two isovector operator first consid-ered by Weinberg, We have considered a setof six ratios R2, which vanish in the limit ofisospin conservation . From these, four involveisovector and isoscalar amplitudes while thetwo others are of purely isoscalar type .

(ii) We have extended the analysis of ref. [4]to higher center-of-mass energies . In the S-wave, isospin violating effects tend to disappear rather quickly in energy. But in the Pi-wave, due to a very small isospin symmetricpart, relative isospin violation becomes verylarge in some ratios . In order to give a morereliable description of the phenomenon, we pre-sented isospin breaking in two other quantities,which are more directly related to the spin-flip and spin-non-flip amplitudes . We concludethat isospin violation effects are small in thesenew projections .

(iii) We have tabulated the theoretical predictionsfor S-wave scattering lengths in the eight phys-ical channels and stressed the importance ofmeasuring the elusive 7r°p channel via precisephotoproduction experiments (which should befeasible at MAMI or the TUNL-FELL) .

We want to note again that within the frameworkpresented here, a unique and unambiguous separa-tion of all different isospin violating effects is possi-ble. To access the size of isospin violation encoded inthe presently available pion-nucleon scattering data,the extension of this scheme to include hard and softphotons is mandatory . Once this is done, it will bepossible to analyze the cross section data directlywithout recourse to any model for separating elec-tromagnetic or hadronic mass effects, thus avoidingany mismatch by combining different approaches ormodels .

References :

N . Fettes, Ulf-G. Meißner and S . Steininger,Nucl . Phys . A640 (1998) 199.

[2]

N. Fettes andUlf-G . Meißner, Nucl . Phys . A676(2000) 311.

[3] N. Fettes and Ulf-G. Meißner, Phys . Rev . C(2001), in print, hep-ph/0008181 .

[4] N. Fettes, Ulf-G . Meißner and S. Steininger,Phys. Lett . B451 (1999) 233.

Two Pion Production on the Proton in Hadronic

S. Schneider, S. Krewald,

Many quark models have problems in describing thefirst positive parity nuclear resonance N*(1440), theRoper resonance. Different interaction mechanisms havebeen employed to account for its low mass. Further in-formation on the structure of the Roper resonance canbe gained by investigating its decay properties .

The Jiilich model for 7rN scattering is based on thesolution of a full coupled channel Lippmann-Schwingerequation . In this approach, resonances can also be gen-erated dynamically through meson-baryon interactionin addition to the genuine qqq poles. With the couplingofthe 7rN channel to the inelastic channels r?N, aN, pN,7rA and 7rN*(1520), the Jülich model can describe the7rN phase shifts and inelasticities up to c.m. energies of1.8 GeV [1].

In particular, the Roper resonance can be generateddynamically by the strong coupling to the aN channel,which serves as a parameterization of a (7r7r)SN state.So it is a logical step to investigate also the two piondecay of the Roper resonance.

We extendthe 7rN model to the reaction 7rN -> 7r7rNby considering the decay of the effective 7r7rN statespN, aN and 7rA . The full relativistic treatment of thethree particle final state interaction is a complex prob-lem which has not yet been solved in general. So we mapthe reaction 7rN -3 7r7rN onto tree-level diagrams as astarting point. The contribution ofthe Roper resonanceis now given by an effective diagram which describes the7rN -+ aN T-matrix of the 7rN model. The couplingconstants and resonance parameters are fixed from the7rN model.

The use of the tree-level model leads to an overes-timation of the total cross sections . This shows thatwe need to include final state interaction effects. Weanalysed the mesonic and baryonic contributions andfound that the 7r7r interaction is dominant in the 7r-p ->7r+7r-n and 7r-p -4 7ro7ron reaction channels. In theabove mentioned 7r7r contribution, the nucleon emits avirtual pion which then interacts with the incoming pionvia p-meson exchange . The non-pole part of this 7r?r in-teraction overestimates the 7r7r cross sections . By includ-ing the final state interaction of the two pions we candescribe both the 7r7r partial wave cross sections andthe7r_P -> 7r+7r-n and 7r-p --> 7roOn total cross sections(see r.h.s. of fig. 1) .

In the 7r+p -+ 7r+7r+n and 7r+p -+ 7r+7rop reactionchannels, the main contribution comes from the excita-tion of a 0 isobar . In such diagrams we have not yetincluded any kind of final state interaction . Already inthe threshold region, our model tends to overestimatethe data in these reaction channels.

The contribution of the Roper resonance (not shownhere) is largest in the 7r-p -> 7r+7r-n and 7r-p -> 7roOnreactions, but even in these channels the contribution isonly marginal . So the pion-induced pion production onthe nucleon is not well suited for studies ofthe two piondecay of the Roper resonance. We nowextend our modelto the ap reaction, where a resonant structure has beennhsprved in thePnemv rpLrion of the Roper rpgonance f21.

120b

10

15

110b

5

and J. Speth

20

10015 [ ittn-' iri'c'n

80

10 1

1 -

1

60b E

f / a 40

1

0.16 0.18 0.2 0.22 0.24Tx [GeV]

Processes

5 I

�

_ -- -1 20

40.16 0.18

0.2

0.22 0.24100.16

0.18

0.2 0.22 0.24

30 [

,r+n -4 ir*,r°n

j

80

604020

:__*--r- , 0200.16 0.18 0.2 0.22 0.24 0.16 0.18 0.2 0.22 0 .24'

,Tx[Gev]

Figure 1: 7rN --+ 7r7rN total cross sections close tothreshold. The solid lines show the results of the fullmodel. The dash-dotted line refers to the sum of alldiagrams involving one or two A isobars. The dashedline shows the contribution of those diagrams where theincoming pion interacts with a virtual pion via p-mesonexchange.

and the electroproduction of nuclear resonances whichis currently measured at Jefferson Lab.

References[1] 0. Krehl, C. Hanhart, S. Krewald, and J. Speth,

Phys. Rev. C 62 (2000) 025207

[2] H.P. Morsch et al ., Phys. Rev. Lett . 69 (1992) 1336

The 7l-photoproduction on the deuteron provides anaccess to the elementary reaction on the neutronand is a general method of investigation the isotopicstructure of the N(1535) photoexcitation amplitude.The separation of the isoscalar and isovector com-ponents is possible by the independent considerationof the y+p-+77+p amplitude, which is given by hy-drogen data, and the y+n-}7l+n amplitude, whichis extracted from deuteron data by means of a con-ventional impulse approximation (IA) .Recently, the preliminary results on photoproduc-tion of ?J-mesons off the deuteron were reportedby TAPS and A2 Collaborations [1]. In Fig. 1 thecross section for inclusive 7l-photoproduction on thedeuteron is displayed as a function of the photonenergy, E., . Our IA calculation is indicated by thedashed line . It reproduces the data reasonably wellfor E y>700 MeV, thus providing the isoscalar tothe proton amplitude ratio of a=0.1 . This result isin agreement with a=0.096±0.02 extracted by thespectator-nucleon experiment [2], but contradicts theanalysis of data on coherent 77-meson photoproduc-tion on the deuteron, which provide substantiallylarger ratio, a=0.20±0.02 [2]. In addition, our pho-ton amplitudes are close to the results from quarkmodel [3] . The deuteron wave function adopted inour IA calculation is obtained from the CD-Bonnmodel [4].

0

1072L600

Incoherent photoproduction of 71-mesons o$' deuterium

yd ->r7np

E,. (MeV)Figure 1 : The cross section for inclusive photopro-duction of 7l-mesons off deuterium. Experimentaldata are taken from Ref. [1]. The dashed line showsthe IA calculation, while the solid line is the resultwith p-n final state interaction.

As evident from Fig. 1, our IA calculation underes-timates the 71-meson photoproduction cross sectionnear the reaction threshold. This underprediction of

A. Sibirtsev and Ch. Elster

the data has been attributed to the final state in-teraction between the neutron and proton [5]. Toaccount for them, we perform the one loop calcula-tions of the neutron-proton (np) final state interac-tion, using half-shell T-matrices obtained from theCD-Bonn model [4] . In Fig. 2 the real part of theT(k, q) is displayed as a function of the off-shell nu-cleon momentum k and for the set of the on-shellnucleon momenta q.

0v

0

aD -20=

0 500 1000 1500

k (MeV/c)

Figure 2: The half-off shell proton-neutron T-matrixas a function of the off-shell momentum k calculatedby CD-Bonn potential model. Here q indicates theon-shell nucleon momentum.

Our calculation including the np final state inter-action is given by the solid line in the Fig. 1 .With the final state interaction the cross section isnow also reasonably well described near the produc-tion threshold . Moreover, since the elementary 7l-photoproduction amplitude is now fixed by the totalreaction cross section, forthcoming data [1] on differ-ential 77-meson spectra at different photon energiescan be used as a verification of our model.References :

[1] V. Metag, Proceedings of the 8-th Int. Conf.on the Structure of Baryons, Bonn (1998), H.Str8her, V. Metag and J. Weiss, private comm.

[2] Hoffmann-Rothe et al ., Phys . Rev. Lett . 78(1997) 4697.

[3]

R. Koniuk and N. Isgur, Phys . Rev. D 21 (1980)1868 .

[4] R. Machleidt, Phys . Rev. C63 024001 (2001) .

[5]

A. Fix and H. Arenh6vel, Z. Phys . A 359 (1997)427.

Coherent dissociation of pions into hard dijets on nuclei

Motivated by the recent data from the E791 Fer-milab experiment [1], where the coherent produc-tion of hard dijets in pion-nucleus collisions 7rA -+Jetl Jet 2 A was studied with a 500 GeV pion beamcolliding on carbon and platinum targets, we inves-tigated the nuclear effects on the dijet productionfrom the multiple scattering of the qq-dipole in thenucleus [2] . The starting point was a construction ofthe pion-nucleon amplitudes 7rp --> qqp, which area building block of the nuclear rescattering problem.The dijet cross section is desribed on the partoniclevel, and we follow the by now standard approach, inwhich diffraction dissociation ofphotonsand hadronsis modelled by excitation of their qq, qqg,, ., Fockstates which are lifted on their mass shell throughthe t-channel exchange of a QCD Pomeron withthe target hadron [3] . The color singlet two-gluonstructure of the Pomeron gives rise to two distinctforward qq' dijet production subprocesses : The firstone, of fig . la, is a counterpart of the classic Lan-dau, Pomeranchuk, Feinberg, and Glauber, [4] mech-anism of diffraction dissociation of deuterons intothe proton-neutron continuum and can be dubbedthe splitting of the beam particle into the dijet, be-cause the transverse momentum k ofjets comes fromthe intrinsic transverse momentum ofquarks and an-tiquarks in the beam particle . Specific of QCD isthe mechanism of fig . 1b where jets receive a trans-verse momentum from gluons in the Pomeron. Aswas shown by Nikolaev and Zakharov [5], the sec-ond mechanism dominates at a sufficiently large kand in this regime diffractioe amplitudes are propor-tional to the differential (unintegrated) gluon struc-ture function Y(x,k2) = aG(x,k2)/alogk2. Corre-spondingly, this mechanism has been dubbed split-ting of the Pomeron into dijets . In diffractioe DIS thePomeron splitting dominates at k >> Q, whereas thesomewhat modified Landau et al . mechanism dom-inates at k < Q. It turns out,that because of thenon-pointlike nature of the 7r -+ qq vertex, it is pre-cisely the Pomeron splitting mechanism which dom-inates at large k. The necessary 7r -+ qqq Fock statelight cone wave function was constructed to be con-sistent with various observables as the pion decayconstant and 7r° decay width into yy as well as thecharge form factor [6] . Furthermore, in the Pomeronsplitting regime diffraction amplitudes are found tobe proportional to the much discussed pion distribu-tion amplitude [7]. The nuclear rescatterings shownin Fig.l lead to two distinct effects: first a broadening of the k-spectrum of dijets through the (mul-tiple) pomeron splitting mechanism, and second toa nuclear attenuation associated with multiple softrescatterings. It turns out that the interplay betweenbroadening and attenuation is controlled by the largek behaviour of the differential gluon density in theproton . The phenomenologically sound gluon density

N.N . Nikolaev, W. Schäfer and G. Schwiete

120

as determined in [8] leads to an intriguing cancella-tion of the broadening and soft rescattering effects .Here we only show our result for the large k asymp-totics of the diffractioe dijet cross section:

References:

dvD _ _21r5dzdk2

27 F~ ~7r (z)Gem (xIPmN)

,p(1xm, k2)

2

3A2as (k2)

2k4 (Reh)

(tC72r (z» 2

21rCAAas (k2)

1

2

Cl+

k2 [2(n7r(z))

;nf +

3(R,h)

G( 2xm'k2)] , (1)

Here the parameter CA N 1 depends slightly on theshape of the nuclear matter distribution, R,:h is thenuclear charge radius, the factor Ge»,(x 2mmr,) de-scribes the effect of finite longitudinal momentumtransfer x]p972N to the target nucleus. Notice thatthe behaviour oc k - s expected from naive dimen-sional counting receives potentially large. correctionsfrom the scaling violations in the unintegrated gluondistribution .W(2x3p, k2) . Remarkably, the leadingtwist term does not contain any free parameters andthus is the perturbatively calculable quantity . The z-dependence of the moment of the pion wave function(n2,(z)) is sufficiently weak and does not precludethe determination of the pion distribution amplitude0,r(z) from the z-distribution of dijets . In fig . 2 weonly show the numerical result of the k dependence ofthe dijet cross section with the (unnormalized) pre-liminary data from E791 . We note in passing that theregion of jet momenta k < 1 .5 GeV is contaminatedby diffractioe excitation of al, 7r', etc, and in this re-gion the use of plane wave parton model formulas isnot warranted. In the pomeron splitting dominanceregion of k > 1 .5 GeV we find good agreement withexperiment . We wish to warn the reader however,that for the kinematics of E791 the dijet cross sec-tion receives huge contributions from higher twists,which is exemplified by the large contribution fromthe second term in the curly braces in the expansion(1) .

[1]

D. Ashery, Invited talk at XInternational Light-Cone Meeting, Heidelberg, June 2000, hep-ex/0008036 .

[2] N.N . Nikolaev, W. Schäfer and G. Schwiete,JETP Lett . 72 (2000) 405; Phys. Rev. D63(2000) 014020 .

(3] N.N . Nikolaev and B.G . Zakharov, Z. Phys . C53(1992) 331 .

[4] L.D . Landau and I.Ya. Pomeranchuk, J. Exp.Theor. Phys . 24 (1953) 505 ; E.L . Feinberg andI.Ya. Pomeranchuk, Nuovo Cim. (Suppl .) 4; R.J .Glauber, Phys . Rev. 99 (1955) 1515 .

N.N . Nikolaev and B.G. Zakharov, Phys . Lett .B332 (1994) 177.

[6] G. Schwiete, Diploma Thesis, University ofBonn, (2000), see also W. Jaus, Phys . Rev. D44(1991) 2851 .

V.L . Chernyak and A.R . Zhitnitsky, Phys .Rept. 112 (1984) 173 ; P. Kroll, 7rN Newslett .15(1999) ; R. Jakob and P. Kroll, Phys . Lett .B315 (1993) 463. Erratum-ibid . B319 (1993)G.P . Lepage and S.J . Brodsky, Phys. Rev. D22(1980) 2157 ; S .J . Brodsky, H.-C. Pauli and S .S .Pinsky, Phys. Rept . 301 (1998) 299.

[8]

I.P. Ivanov and N.N . Nikolaev, hep-ph/0004206 .

[9] N.N . Nikolaev and B.G. Zakharov, Z. Phys .C49 (1991) 607 .

d)

Figure 1 : Sample Feynman diagrams for diffractivedijet excitation in 7rN collisions diagrams la),lb)Jand typical rescattering corrections to the nuclear co-herent amplitude (diagrams ic),ld),le)J.

k [GeV]

Figure 2: The E791 data [1] for the differentialdiffractive dijet cross section dv/dk for the 196pt tar-get with the theoretical calculations. The data are notnormalized . The dash-dotted and dashed lines showthe contributions from various helicity amplitudes .The solid line is the total result .

Diffractive structure function at very small P and unitarity corrections in the color dipoleapproach

One of the prominent findings of the HERA physicsare the diffractioe deep inelastic processes (DDIS)-y*p -~ Xp which make up on the order of 10%of the total virtual photoabsorption cross section.Now it is well known, that the opening of diffractioechannels comes along with the absorptive (screen-ing,shadowing,unitarization) correction to the totalcross section. In particular the absorptive correctionsspoil the property of the total photoabsorption crosssection being a linear functional of the parton den-sities, upon which assumption all two-parton lad-der perturbative QCD phenomenology of deep in-elastic structure functions is based. While the DDISdata from HERA indicate that the unitarity effectsat HERA cannot be much stronger than the abovementioned 10% it is nevertheless interesting to ex-plore the region of high mass diffraction (the diffrac-tive structure function at very small P), which willdrive the unitarity corrections at still higher energies .The particularly well suited approach, which allows aconsistent treatment of diffactive channels as well asofthe total cross section at small x is the color dipoleapproach ([1]) . Deep inelastic scattering at large val-ues of the Regge parameter 1/x = (WZ +QZ)IQ' »1 ( with Wa = (p -{- q)2 the y*-target cms-energysquared, and Q2 = _q2, the photon virtuality) isconveniently viewed in terms of the scattering of theqq color-dipoles of sizes r and r' in the photon andtarget t respectively . Making use of the color dipole(CD) factorization the y*t cross section takes theform:

U,y* (x, Q2) =1 dzd2rdz'd2r' ilpy . (z, r) ( 2

Here JAFy " ,t(z,r)i2 denotes the probability to find aqq dipole of tranverse size and orientation r in the-y*, t with a partitioning z,1- z of the -/*, t-lightconemomentabetween its constituents . The principal dy-namical quantity of the color dipole approach isthe dipole-dipole cross section v(x, r, r'), whose x-dependence is governed by a generalized BFKL equartion, for details see [2]. Diffractive processes emergenaturally as the quasielastic scattering of the qq(small diffractioe masses M, large fl = QZ/(Q2+M2)and qqg (large M, small P) components of the virtualphoton . While the former can be reinterpreted withsome care in terms of the valence quark content of thePomeron, the latter can be associated with the pho-toabsorption on a sea-quark in the Pomeron, whichin turn was radiatively generated from a 'valence-gluon' in the Pomeron. The corresponding two-gluonwavefunction of the Pomeron was derived in (1] :

ITrn(zg,P,xrn)i2oc s [agg(PZII',P) ] . ..~(R~)

N.N . Nikolaev, W. Schäfer and V.R . Zoller*

I9Yt(z', r')12 . a(x, r, r') .

122

and is the starting point of our generalization of theCD-Regge expansion to diffractioe DIS (DDIS) . Twomajor conclusions follow : first, the two gluon wave-function prescribes how the Pomeron enters as a tar-get in the CD-Regge expansion, which can now bestraightforwardly applied to the diffractioe structurefunction, alias the y*IP total cross section. This al-lows us to build up the full %ß-dependence associatedwith the triple-IP regime of DDIS at fixed value ofxjp . And second, we make the crucial observationthat the strong dependence on x]p must be subjectto the unitarity constraints for the s-channel par-tial waves. In view of the parameter R'IR22 « 1,the natural quantity is the dipole-quark scatteringprofile function (s-channel partial wave amplitude)

-b2ro(x~ , P, b) = 3

47rB(x))

exp [2B(xip)1 .

Here Egg is the cross section for scattering of a gg-dipole on a nucleon, and the Regge slope B(xip) =1/3R,' -I- 2a1P log(xo/xm), a'a, N 0.07GeV- 2.The essence of s-channel unitarity is the boundI'(xi , p, b = 0) <_ 1 on the relevant partial waveswhich we achive by means of plugging the bare 1'ointo an eikonal formula yielding the unitarized crosssection au (x1p, p), and hence the unitarity correctedJTrn(zg,p,xn')12 . Our procedure sums the multi-pomeron exchanges which couple to the lowest laddercell in the cut Pomeron, and hence allow the full fl-span to evolve from small size 1/Q at the y* vertexto large size R,~ at the lower end [1] . At small P thisarguably dominates the much popular fan diagramsummation. An estimate of the absorptive correctionto the proton structure function can be obtained byintegrating the diffractioe cross section over masses .Our calculation gives Rsh = AshF2p/F2p N 0.3 atx N 10-4 , Q2 = 1GeV2 growing to Rsh N 0.35 atx N 10-6 . Hence we see no sign of reaching the blackdisc limit R, h = 0.5 anysoon . However we stress thatthe found unitarity corrections are large enough toprovide a substantial systematic uncertainty for alltwo-parton ladder based DIS-phenomenology.References:[1] N.N . Nikolaev and B.G. Zakharov Z. Phys . C

64 (631) 1994(2] N.N . Nikolaev, B.G . Zakharov and V.R .

Zoller, JETP Lett. 59 N.Nikolaev et al .Phys.LettB473,157(2000)

[3] M.Genovese et al . JETP81, 625,633(1995) ; M.Bertini et al . Phys . Lett.B 422;238,(1998) ;

[4] N.N . Nikolaev, W.Sch9fer, and V.R . Zoller, inpreparation .

* ITEP, Moscow, Russia

Anatomy of the differential gluon structure function of the proton from the experimental dataon F2p(x, Q2)

In the last 20 years the DGLAP approach has pro-vided a very successful description of many high-energy scattering processes of hadrons. The quarkand gluon integral densities, being the key quanti-ties for this description, have become the most stud-ied objects in particle phenomenology. In particular,several groups, notably GRV, MRS and CTEQ, haveworked out convenient parameterizations for thesedensities, which incorporate the DGLAP dynamicsup to NLO.However, it has been understood for a long time thatthe approximations the DGLAP approach rests onbecome unjustified in the very low xBj domain . Infact this is precisely the applicability domain of theBFKL dynamics, known also as the rc-factorizationapproach . The principal quantity here is the fully dif-ferential gluon structure function (DGSF) .T(x, r.2),for which unfortunately no convenient parameteriza-tion has been developed. The detailed understandingof its behavior, its properties, and the level of arbi-trariness it entailes upon being included in the cal-culations have also been lacking. All this definitelyconstituted a serious impediment to the quantitativeanalysis of many high-energy reactions within the rc-factorization approach.In the present work we fill this blank. We first de-termine the form of DGSF from experimental dataon F2p and then bring it under close scrutiny.Our Ansatz for DGSF is partially built on the avail-able parameterizations of the integrated DGLAPgluon densities with a proper extrapolation into thesoft domain . So built gluon density constitutesthe hard part of the DGSF; we then accompanyit with a purely soft non-perturbative part . Thenrc-factorization predictions for the proton structurefunction F2p(x, Q2) based on so-constructed gluondensity are tested against the data in the entiredomain of Q 2 , and the set of parameters allowingfor the best fit is obtained . The net result of thisphenomenological determination of the unintegratedgluon structure function from the experimental dataconsists in compact, simple, ready-to-use parameter-izations of .f(x, rc 2 ) (Fig . 1), which can now be ana-lyzed and used for computation of high-energy pro-cesses .Having determined the form of the differential gluondensity, we turn to investigation of its properties .First, we analyze soft-to-hard decomposition of theDGSF itself and of the intergated quantities G(x, Q 2)and F2p(x, Q2) . We observe two remarkable proper-ties of soft-to-hard diffusion, the intrinsic feature ofthe rc-factorization approach . We find that predom-inantly hard gluons influence the integrated quanti-ties even at Q2 = 0. In particular, the hard part ofDGSF is solely responsible for the energy rise of thetotal real photcabsorption cross section (in a sharp

I.Ivanova ,b, N.Nikolaeva ,a

123

contrast to Donnachie-Landshof type models, wherethe rise ofpomeron soft component is explicitly intro-duced) . The same diffusion phenomenon leads alsoto intrusion of soft gluons into large Q 2 domain, caus-ing non-decreasing and even rising soft contrubutionto intergrated quantities . For example, for not toosmall xB.1 (XBj - 10'3), the non-perturbative partof F2p dominates up to Q2 - 10 GeV2 .Another insight into the properties of DGSF is givenby analysis of energy rise both of DGSF itself andof integral quantities . This energy rise can be conve-niently represented in terms of effective intercepts .We found that the effective intercept of the hardpart of DGSF is a quickly varying function of Q 2 ,which leads to similar fast Q2-variation of the to-tal interceps of DGSF (recall that in our Ansatz thesoft piece of DGSF is energy-independent) . However,when we switch to the proton structure function F2p ,

we observe a dramatic flattening of the hard inter-cept . Thus we find that proton structure functionF2p naturally allows for a simple Regge /picture :it can be contructed from energy-independent softpart and almbst fixed-pole hard piece with interceptAhard - 0.4 .

Fig. 1 : Differential gluon structure function .T(x, r.2 )as a function of rc 2 at several values of x .

Dashed and dotted lines represent the soft and

hard components; the total unintegrated gluon

density is shown by the solid line .

"Institut für Kernphysik, Forschungszentrum Jülich,bNovosibirsk University, Novosibirsk, RussiaLandau Institute for Theor. Phys ., Moscow, Russia

References:(1] I.P . Ivanov and N.N . Nikolaev, hep-ph/00%206,

preprint FZJ-IKP-TH-2000-08, submitted to Eur.Phys.J . C.

CP-odd anomalous interactions of Higgs boson in its production at photon colliders

The Standard Model, being based on the Higgsmechanism of providing mass to gauge bosons, hasbeen extremely successful so far. Though the Higgsboson itself has not yet been experimentally found,the majority of researchers does believe in its exis-tance. So, currently the principal question of the-oretical investigation is not "How to find the Higgsboson?" but rather "What else can be learned withits help?" .This is precisely the question we answer in our work .Namely, if there is some New Physics beyond theStandard Model, what observable phenomena canone expect when studying the Higgs boson proper-ties? In particular, what can be told about the CPnature of the Higgs boson and of new interactions (ifthey are present)?We argue that the best way to answer these ques-tions is given by the study of the Higgs boson(s) in-teraction with photons. The motivation is twofold .First, due to their natural suppression in the Stan-dard Model, the Hyy and HZy couplings are verysensitive to possible new interactions . Second, thefuture experiments at photon colliders, which are be-ing planned these days, will be featured by a veryhigh level of cleanness of events, of energy resolu-tion and of control of colliding photons polarizationstates . In our work [1] we use these advantages of thephoton colliders to find out how and up to what ac-curacy this or that type of anomalous interactions,especially those that violate CP parity, can be ob-served . This work is in fact a natural follow-up ofour recent paper [2], where we conducted a similarinvestigation in the case of CP-conserving anomalies .We first wrote down the most general form of theHyy and HZy interactions, which include both theStandard Model contributions and the anomalies .Since we aimed at accounting for the most broadclass of anomalies, we did not place any specific re-strictions on the magnitude or on the phase of newinteractions . Then, we focused on two reactionsyy --+ H and ey -+ eH and determined the polariza-tional and angular asymmetries, sensitive to differ-ent parameters of anomalies. In fact, we developedthe whole strategy of searching for the New Physicsat the photon colliders : we showed how to analyzesimultaneously both reactions and how to extract in-formation about the underlying interactions from thedata.Finally, given prospects of the experimental accuracythat will be achievable in these two reactions, we de-duced the numerical predictions for the magnitudeof the effects. Translated into the energy scales ofthe New Physics phenomena (in the case when thenon-standard phenomena indeed have the high en-ergy origin), the limits read A ti 40 -'. 60 TeV foranomalous Hyy interactions and A 20 TeV forHZ-1 anomalies . Note that the exact number will

I.Ivanov'>b, I F. Ginzburgb

depend on the phases of anomalous terms.Last, for the purpose of illustration of the generalmethod, we applied our scheme to a very specificanomaly: deviations from the Standard Model dueto the two doublet structure of the Higgs sector . Wegave numerical predictions for the most importantasymmetries and explained how the strategy changesfrom low to high tan ,Q region .Institut für Kernphysik, Forschungszentrum Jülich,

bInstitute of Mathematics, Novosibirsk, Russia

References :[1] I.F . Ginzburg, I.P . Ivanov, hep-ph/0004069, preprint

FZJ-IKP-TH-2000-07, submitted to Phys.Rev.D .[2] A.T . Banin, I.F. Ginzburg, I .P. Ivanov, Phys. Rev .

D 59 (1999) 115001

At high quark chemical potential, quantum chromo-dynamics (QCD) is accessible to weak coupling anal-ysis, where the ground state exhibits a robust super-conducting phase, with novel and nonperturbativephenomena [1] . QCD superconductors in the color-flavor-locked (CFL) phase support excitations (gen-eralized mesons) that can be described as pairs ofparticles or holes (rather than particle-hole) arounda gapped Fermi surface.In this paper [2], we have pursued the microscopicanalysis for the generalized scalar, vector and ax-ialvector mesons viewed as composites of pairs ofquasipaxticles or quasiholes in the CFL phase.We have shown that in the CFL phase the scalarexcitations are massless as it is the case for the pseu-doscalar excitations already discussed in [3] . The lat-ter are true Goldstone modes, while the former arewould-be Goldstone modes that combine with thelongitudinal gluons leading to the Meissner effect inthe CFL phase. In other words, the scalar modes areHiggsed by the gluons .Furthermore, we have shown that bound vector andaxial-vector excitations of particles or holes exist inthe CFL phase, and have derived an explicit relationfor their form factors and masses. To leading loga-rithm accuracy the octet of vectors are degeneratewith the octet of axial-vectors, irrespective of theirpolarization . Chiral symmetry is explicitly realizedin the vector spectrum in the CFL phase in lead-ing logarithm approximation, in spite of its breakingin general. The mass of the composite vector exci-tations is close to and bounded by twice the gap inweak coupling 2Go, but goes asymptotically to zerowith increasing coupling thereby realizing Georgi'svector limit [4] in cold and dense matter. In the CFLsuperconductor the vector mesons are characterizedby form factors that are similar but not identical tothose of the generalized pions.Furthermore, we have shown that the composite vec-tor mesons decouple from the Noether currents andthat they do not decay to pions in leading logarithmaccuracy, contrary to their analogues in the QCDvacuum. Moreover, they decouple from the gluons inthe CFL phase as well .We have explicitly shown that the composite vectormesons can be viewed as a gauge manifestation ofa hidden local SU(3),:+v when their size is ignored(their form factor set to one) . In this limit, the effec-tive Lagrangian description suggested in [5, 6, 7] isvalid with the vector mesons described as Higgsedgauge bosons . Only in this limit, which is clearlyapproximative, do we recover concepts such as vec-tor dominance and universality [8] . (This is of coursewhat one would expect in the normal phase as well .)In summary, a hidden local symmetry can only berevealed for zero size pairs, which is not the case formagnetically bound pairs. In other words, the zero-

Generalized Mesons in Dense QCD

M. Rho (Saclay), E. Shuryak (Stony Brook), A. Wirzba and I. Zahed (Stony Brook)

125

size limit is not compatible with the weak couplinglimit, because of the long-range pairing mechanismat work at large quark chemical potential .The existence of bound light scalar, vector and axial-vector mesons in QCD at high density, may haveinteresting consequences on dilepton and neutrinoemissivities in dense environments such as the onesencountered in neutron stars. For example, in youngand hot neutron stars neutrino production via quarksin the superconducting phase can be substantiallymodified if the vector excitations are deeply boundwith a non-vanishing coupling, a plausible situationin QCD in strong coupling, or by P-wave couplingto the massless scalar excitations . These excitationsmay be directly seen by scattering electrons off com-pressed nuclei (with densities that allow for a super-conducting phase to form) and may cause substan-tial soft dilepton emission in the same energy rangein "cold" heavy-ion collisions .

References :

[2] M. Rho, E. Shuryak, A. Wirzba and I. Zahed,Nucl . Phys. A676, 273 (2000) .

[4) H. Georgi, Phys . Rev. Lett . 63, 1917 (1989) ;Nucl . Phys. 13331, 311 (1990) .

[6] R. Casalbuoni and R. Gatto, Phys. Lett . B464,111 (l999) .

B. C. Barrois, Nucl . Phys. 13129, 390 (1977) ;D. Bailin and A. Love, Phys . Rep. 107, 325(1984) ; M. Alford, K. Rajagopal andF. Wilczek,Phys. Lett . 13422, 247 (1998) ; R. Rapp,T. Schiifer, E.V . Shuryak and M. Velkovsky,Phys. Rev. Lett . 81, 53 (1998) ; M. Alford, K.Rajagopal and F. Wilczek, Nucl . Phys . B537,443 (1999) ; T. Schäfer and F. Wilczek, Phys.Rev. Lett . 82, 3956 (1999) ; see F. Wilczek,Nucl . Phys . A663, 257 (2000) and T. Schäfer,nucl-th/9911017 for recent reviews.

M. Rho, A. Wirzba, I. Zahed, hep-ph/9910550,Phys. Lett . B 473, 126 (2000) .

D. K. Hong, M. Rho and I. Zahed, Phys. Lett .13468, 261 (1999) .

D. T. Son and M. A. Stephanov, Phys . Rev. D61, 074012 (2000) .

[8] M. Bando, T. Kugo, S. Uehara, K. Yamawakiand T. Yanagida, Phys . Rev. Lett . 54, 1215(1985) .

M. A. Nowak (Cracow), M. Rho (Saclay), A. Wirzba and I. Zahed (Stony Brook)

At high quark density, QCD exhibits a supercon-ducting phase with novel and nonperturbative phe-nomena [1, 2] . For degenerate quark masses theQCD superconductor breaks color and flavor sponta-neously with the occurrence of Goldstone modes [3]in the form of particle-particle or hole-hole excita-tions. These modes (generalized piones) were ana-lyzed recently using effective Lagrangians [4, 5, 6](zero size) and bound state equations [7, 8] (finitesize) .In the present letter[9] we have analyzed the decayprocess *° -* yy of the generalized pion fro into apair of modified photons y using weak-coupling ar-guments at large quark chemical potential p.In the CFL phase the ordinary photon is screened,and the gluons are either screened or higgsed . How-ever, it was pointed out in Ref. [3] that the CFLphase is transparent to a modified or tilde photon,

A,, = A,, cos 0 +HP sin 0 .(1)Here A. is the ordinary photon field which cou-ples to the charge matrix e Q.. = e diag(2/3,1/3,1/3) of the quarks,' and H,, is the gluon fieldfor U(1)y where gY = g diag(-2/3,1/3,1/3) isthe color-hypercharge matrix . Furthermore, cos 0 =g/

e2 + g2, and sin 0 = e/

e2_+ g2 . A,, carriescolor-flavor and tags to the charges of the Goldstonemodes. The quark coupling to the tilde photon isin units of e = ecos 0. As a result, the CFL phaseis characterized by generalized flavor-color anoma-lies [4]. We have shown in Ref. [9] that the triangleanomaly emerges from a direct calculation of the de-

Figure 1: Leading contributions to jr° --> y~ in the CFLphase. The crosses refer to pair-condensate insertions .

cay of the generalized pion into two generalized pho-tons, fro -+ ;y~, in the leading logarithm approxima-tion, i.e . the amplitude reads

T3)l~v

17P2) = 47rFT

I T3 Q2l e~vaß p1 jj.20 (2)

(with

Here FT is the time-like decay con-stant of the generalized pion in the superconductingphase, p1 and p2 are the momenta of the modifiedphotons . The result (2) is consistent with the modi-fied triangle anomaly

2

_ _ä,a A3

2

4

96,r2 em,paFg"FP'

(3)suggested by the generalized Wess-Zumino-Witten(WZW) term [4] . Here F" is the field strength asso-ciated to Eq . (1) . Note that the conventional triangle

pro -+ yy in Dense QCD

anomaly is larger by a factor N, This factor is ab-sent here, because of the color-flavor locking of thequarks . Furthermore, the internal line between thetwo generalized-photon vertices in Fig. 1 has to cor-respond to an antiparticle . Therefore, the amplitude(2) does not have an explicit t12 dependence whichnaively would be expected from the momentum in-tegration around the Fermi surface. In fact, becauseof the dependence on FT = ti/7r [6, 7], the radiativedecay of the generalized pion (2) vanishes as 1/,u indense matter .To leading logarithm accuracy our result is exact andin agreement with the normalization suggested bythe generalized WZWterm given in [4] . Much like inthe vacuum, the radiative decay of the generalizedpions is dictated by geometry in leading order, andvanishes at asymptotic densities. Clearly our analysisextends to other anomalous as well as nonanomalousprocesses, and should prove useful for the analysis ofemission rates in dense QCD.

References:

B . C. Barrois, Nucl. Phys . 13129, 390 (1977) ;D. Bailin and A. Love, Phys . Rep. 107, 325(1984) ;

[2] M. Alford, K. Rajagopal and F. Wilczek, Phys .Lett . B422, 247 (1998) ; R. Rapp, T. Schäfer,EX. Suuryak and M. Velkovsky, Phys . Rev.Lett . 81, 53 (1998) .

M. Alford, K. Rajagopal and F. Wilczek, Nucl.Phys . 13537, 443 (1999) ; T. Schäfer and F.Wilczek, Phys . Rev. Lett . 82, 3956 (1999) .

[4] D. K . Hong, M. Rho and I. Zahed, Phys. Lett.B468, 261 (1999) .

[5]

[6] D. T. Son and M. A. Stepuanov, Phys . Rev. D

[7]

[8] M. Rho, E. Shuryak, A. Wirzba and I. Zahed,Nucl . Phys . A676, 273 (2000) .

[9]

R. Casalbuoni and R. Gatto, Phys. Lett . B464,111 (1999) .

61, 074012 (2000) .

M. Ruo, A. Wirzba, I. Zahed, Phys . Lett . B473, 126 (2000) .

M. A. Nowak, M. Rho, A. Wirzba and I. Zahed,Phys . Lett . 13497, 85 (2001) .

Instantons As Unitary

M. Napsuciales (Leon), A. Wirzba

The incorporation of the strange (s) quark as athirdflavor degree of freedom into a larger unitary-groupsymmetry is not necessarily unique . Usually, SU(2)udis extended to U(3)uds unitary-spin. This extensionwas in particular justified by the mass compilationof mesons to nonets - the vectorial U(3)uds represen-tation . The matrices representing the diagonal threeflavor generators were chosen in such a manner thatan octet flavor state, i.e . 18) = (üu+dd-2ss)/v/6_,and a singlet flavor state, i.e . 11) = (i1u+dd+ss)l,\,F3,were to appear . This generator choice is referred toas Gell-Mann's octet-singlet basis and it predicts thewave functions of the isoscalar physical mesons tobe patterned correspondingly. Amazingly, only thewave functions of the pseudoscalar and axial-vectormesons are dominated by octet or singlet states .Gell-Mann's basis does not apply to spin-1-- vectorand spin-2++ tensor mesons, where one observes aclear separation between strange, Is) = ss, and non-strange, ins) = (icu+dd)/,/2_ isoscalar quarkonia.It was argued in Ref. [1] that the flavor symmetry forvector mesons respects the quark generations, i.e . itis given by SU(2)ud ® SU(2) cs ® U(ludcs) consid-ered in the limit of heavy spectator c quarks. In thatcase, the diagonal flavor generators are representedby diag(l, -1) and act upon the lst and 2nd quarkgenerations, respectively, while U(1)udcs invariance isassociated with quark-baryon-number conservation.Within this framework, octet and singlet flavor forunnatural parity mesons such as 0-+ and 1++ ap-pear as an artifact of the quark-generation mixingdue to effects brought about by the U(ludcs)A gluonanomaly. To explain the phenomenon of conflictingflavor symmetries for the anomaly-free mesons, onthe one hand, and the anomalous meson sectors, onthe other hand, a rule has been invoked (the so-calledOkubo-Zweig-Iizuka (OZI) rule [2]) that suppressesdisconnected planar (hairpin) gs-iau/dd diagrams .The OZI rule is well respected within the sectorsof the anomaly-free spin-1-- vector and spin-2++mesons . There, it takes its origin in a destructiveinterference of non-planar KK* and KK* loop dia-grams with such containing KK, and K*K*, respec-tively, an observation due to Lipkin [3], and moreimportantly, in the suppression of hairpin diagramsdue to the absence of gluon anomaly effects in thesesectors.For the anomalous sectors of the pseudoscalar andaxial vector mesons, where instanton effects are ex-pected to be substantial, the OZI rule is stronglyviolated . In addition to this strong violation, theremight be other subleading mechanisms breaking theOZIrule, e.g. the incomplete cancellation of the non-planar diagrams due to the absence of the parity-forbidden KK loop diagram [4] . In fact, the scalarmeson sector is more sensitive to such subleadingOZI breaking effects than the pseudoscalar sector .

127

and M. Kirchbach (Zacatecas)

These interfere destructively with the instanton-induced contribution to the mixing, such that thescalars are less strongly mixed than pseudoscalarsand thus again closer to the flavor basis.

It is the goal ofthe present study [5] to show that uni-tary spin is an accidental symmetry due to anoma-lous dynamics that appears preferably for unnaturalparity mesons such as 0-+ and 1++ under the um-brella of the instanton-induced quark-quark interac-tions. We illustrate the formation of the "eightfoldway" within a linear sigma model with 't Hooft' s de-terminantal flavor-dependent interaction, such thatthe mixing of non-strange and strange quarkonia (seealso [6]) in the wave function of the physical 77 me-son is accidental . Especially, we expect that the cou-pling of the 77 to the nucleon does not follow theoctet-singlet scheme, but rather the non-strange-strange scheme, i.e . the (flavor-)coupling-eigenstates(nn" and r7$) should be distinguished from the mass-eigenstates (the physical 77 and rl') . We explore con-sequences of this new coupling scheme for the effec-tive r7-nucleon coupling constant which, according toan old analysis of Ref. [7]'on forward NN. disper-sion relations and a new analysis of Ref. [8] of thedifferential cross sections in the 77 photo-productionofdproton near threshold at the Mainz Microtron(MAMI) [9], is smaller than naively expected in theoctet-singlet scheme.

References :

[2] S. Okubo, Phys. Lett . 5, 165 (l963);G. Zweig, CERN Report No 8419 TH 412(l964) ; J. Iizuka, Prog. Theor. Phys . Suppl. 37-38, 21 (1966) .

Spin Maker

M. Kirchbach, Phys . Rev. D58 117901 (1998) .

H. J. Lipkin, Nucl . Phys. B244, 147 (l984) ;

ibid. B291, 720 (1987) .

[4]

H. J. Lipkin and B. Zou, Phys . Rev. D53, 6693

(1996) ; B . Zou, Phys . Atom. Nucl . 59, 1427

(1996) .

M. Napsuciale, A. Wirzba and M. Kirchbach,FZJ-IKP(TH)-2000-24, to be published.

[6] T. Feldmann, Int. J. Mod. Phys . A15, 159

(2000) .

W. Grein and P. Kroll, Nucl. Phys . A338, 332

(1980) .

[8]

L. Tiator, C. Berrhold and S. S. Kamalov, Nucl .

Phys . A580, 445 (1994) .

B. Krusche et al., Phys. Rev. Lett. 74, 3736

(l995) .

Casimir Interaction among Objects Immersed in a Fermionic Environment

In 1948 Casimir predicted the existence of a very pe-culiar effect, the attraction between two metallic par-allel plates in vacuum [1]. The existence of such anattraction has been confirmed experimentally withhigh accuracy (for a different geometry) only re-cently [2]. The origin of this attractive force can betraced back to the modification of the spectrum ofzero point fluctuations of the electromagnetic field .Similar phenomena are expected to exists for variousother (typically bosonic) fields [3, 4] and the corre-sponding forces are referred to as Casimir or fluctu-ating interactions . A related interaction arises whenthe space is filled with (noninteracting) fermions,which is particularly relevant to the physics of neu-tron staxs [5] . One of the simplest cases correspondsto nuclei embedded in a neutron gas. These how-ever could be replaced with buckyballs immersed inan electron gas, in liquid mercury for example. Par-ticularly attractive candidates for the study of theCasimir effects in essentially perfect degenerate fermisystems are the dilute atomic Fermi condensates [6].In the case of two parallel impenetrable planes, di-mensional arguments suggest that the dependence ofthe Casimir energy for fermions on the distance be-tween the two planes has the form EC = ftF(kFd),where p = h2kF/2m is the chemical potential, kFis the Fermi wave vector and d is the distance be-tween the two planes . For this simple geometry it isstraightforward to evaluate the function F(kFd) [5] .One has to be careful and specify whether the calcu-lation should be performed at fixed particle numberor fixed chemical potential, as one can easily showthat the Casimir energy has a different behavior inthese two limits .For more complicated geometries the evaluation ofthe Casimir energy is generally a rather involved,even though straightforward, numerical procedure .Ourmain goal is to reach a qualitative understandingof the Casimir energy in the case of complicated ge-ometries . In Ref. [7] we consider mainly two obviouslimits, when the objects immersed in the Fermi envi-ronment are either much smaller or much larger thanthe Fermi wave length . We show there that the caseof large scatterers can be treated quite accuratelyusing semiclassical methods at practically all sepa-rations. The most important conclusion we are ableto draw from our study however is that the Casimirinteraction energy in the case of more than two scat-terers can be evaluated quite accurately as a sum ofpairwise interactions between these scatterers . Thisconclusion comes to some extent as a surprise, sinceit is known that Casimir energy is not pairwise ad-ditive .In order to be specific, we have considered in [7] thecase of three and four spheres as a generic modelfor more complicated geometries . For such n-objectsystems there exist periodic trajectories (or stand-

A. Bulgac (Seattle) and A. Wirzba

128

ing waves) bouncing off three or more such objectsand thus the contribution to the density of statesand to the Casimir energy due to such orbits de-pends on the relative arrangement of three or moreobjects, thus leading to genuine three and more bodyinteractions . We observed however that the contri-bution of three or more bounce orbits to the densityof states, and thus to the Casimir energy as well,is never dominant . An analysis of the stability ma-trix of an n-bounce orbit shows that its contributionto the integrated density of states at large distancesis proportional to 1/Ln, where L is the length ofthe orbit, if all the legs of the orbit are comparablein length . Any person who ever played pool (thusin 2D) knows instinctively that long shots are moredifficult than short ones and that the most difficultshots are the many bounce shots. In 3D and higherdimensions orbits are typically more unstable than in2D. An exact evaluation of the stability matrix forvarious periodic trajectories shows that even at smallseparations the contributions of two bounce periodicorbits dominate over the contributions of three ormore bounce periodic orbits . We thus infer that forsufficiently smooth objects, whose various geometriccharacteristic lengths are larger then the Fermi wavelength one can use the simplest semiclassical approxi-mation (the contribution due shortest periodic orbitsonly) to evaluate the Casimir energy. We have alsoshownthat the Casimir energy for several objects canbe represented fairly accurately as a sum of pairwiseCasimir interactions between pairs of objects.

References:

[1] H.B.G . Casimir, Proc . K. Ned. Akad. Wet. 51,793 (l948) .

[2] S. Lamoureaux, Phys . Rev. Lett, 78, 5 (1997) ;81, 5475(E) (1998) ; U. Mohideen and A. Roy,Phys. Rev. Lett . 81, 4549 (1998) .V.M. Mostepanenko and N.N . Trunov, TheCasimir Effect and its Applications. ClarendonPress, Oxford (1997) ; M.E . Fisher and P.G. deGennes, C.R. Acad . Sci. Ser. B 287, 207 (1978) ;A. Hanke et al ., Phys . Rev. Lett . 81,1885 (1998)and references therein.

[4]

M. Kardar andR. Golestanian, Rev. Mod. Phys .71, 1233 (1999) and references therein.

[5]

A. Bulgac and P. Magierski, Nucl . Phys . A383,(2001) and astro-ph/0002377 and referencestherein.

[6] B. Demarco and D. S. Jin, Science 285, 1703(1999) .

[7]

A. Bulgac and A. Wirzba, to be published

4. NUCLEAR STRUCTURE AND REACTIONMECHANISM

Study of the giant monopole resonance in 4°Ca hasa long story, see, for example, [l, 2, 3] and is of greatinterest for several reasons: (1) it is a bridge betweenthe sd and fpnuclei and till very recently there wereproblems connected with the missing of the isoscalarmonopole strength in nuclei with A<90 [l, 4] . (2)Recent 4oCa(a, a') experiments with E, = 240 MeVat small angles including 0° for the first time gave alarge depletion (92 f 15)% of the IS EO EWSR (inthe (8 - 29) MeV interval) [2] . They have confirmed adistinct structure of the IS EO strength. This struc-ture is a challenge for any microscopic theory.Our microscopic calculations [4] describe satisfacto-rily the IS EO resonance in 40 Ca (2] including itsstructure. Earlier, similar calculations by our groupfor 58Ni explained reasonably well not only the ISEO resonance in this nucleus but also the total spec-tra see [4] . Our predictions have recently been con-firmed by the improved 58Ni(a, a') experiments [5].In the present approach we calculate total spectra ofthe 40Ca(a, a')reaction observed in [2]. They havealso a detailed structure but, unfortunately, only as"counts" .

50

20oU

W 10y0U

0

Microscopic description of total spectra in 40Ca(a, a') at Ea = 240 MeV.

5 10 15 20 25Energy (MeV)

S.Kamerdzhiev*, J.Speth, G.Tertychny*

30

Fig.1 Cross sections of 40 Ca(a, a') at Ea = 240 MeVand 9 = 1.1°. The experimental data (dotted line)and the background (dot-dash line) are taken fromRef. [2], Because in.Fig .2 of [2] there are only counts,the experimental hystogram was imposed on the the-oretical curve in such a waythat the maxima of bothcurves coincided. In this way it was possible to es-timate roughly the contribution of the instrumentalbackground as the difference between two horizontalaxes, see text .

We used the same theoretical method [4] as in thecalculations for "Ni. The method took into ac-count all three known mechanisms of giant reso-nance damping, namely the RPA or Landau damp-ing, the spreading width caused by more complexlplh®phonon configurations and the escape widthdue to the inclusion of the single-particle continuum.Because of the energy-dependence of the microscopictransition densities, the energy interval consideredwas divided into 5 MeV bins for which the calcula-tions were performed separatly. For 40Ca, however,it was necessary to use the 2 MeVbins because the ISEO strength and total spectra are much more struc-tured than those in 58Ni. Like In the case of 58Nithe contribution of the IS and IV El and IS E0, E2,E3, E4 resonances has been taken into account andsummed to obtain the final total spectra. These res-onances were calculated within our model with thesame parameters of the Landau-Migdal interaction.

We obtained the following results shown in Fig.l :1.The microscopic theory which uses known andfixed parameters of the interaction describes reason-ably well gross structure of total spectra, except forthe region below 9 MeV which may be connectedwith the excitations of the (a+3sAr) system.2.The difference between two horizontal axes in Fig.1gives an instrumental background of the experi-ment under discussion. This difference is about7 mb/srMeV so that the integrate cross section isabout 7x25 = 175 mb/sr.( These numbers are, ofcourse, very preliminary because they were obtainedfrom imposing the experimental curve on the theo-retical one) . Integration o£ the theoretical curve gives422mb/sr and for the experimental onewe obtained676 mb/sr. So we should compare (676-175) = 501mb/sr (experiment) and 422mb/sr(theory) .3.As can be seen from Fig.1 , the experimental back-ground shown by the dot-dash line contains a notice-able contribution ofgiant resonances including the ISEO one.

References:[1] A. van der Woude, Nucl . Phys . A649, 97c

(1999) .[2] D.H . Youngblood, Y.W. Lui, and H.L . Clark,

Phys . Rev. C 55, 2811 (1997) .[3] S. Kamerdzhiev, J.Speth, G. Tertychny, Nucl .

Phys . A624, 328 (1997)[4] S. Kamerdzhiev, J. Speth, G. Tertychny, Eur.

Phys. J. A 7, 483 (2000) ;IKP Annual Report 1996, p.201 .

[5] Y.-W, Lui, H.L . Clark and D.H . Youngblood,Phys.Rev. C 61, 067307 (2000) .

*The Institute of Physics and Power Engineering,249020 Obninsk, Russia.

Coulomb Dissociation as a Tool for Nuclear Structure and Astrophysics

G . Baur,S.Typel*,H.H.Wolter**,K .Hencken***,and D.Trautmann***

Parts of this work are published in Ref.[l, 2, 3) . Sincethe perturbation due to the electric field of the nu-cleus is exactly known, firm conclusions can be drawnfrom Coulomb dissociation measurements . Electro-magnetic matiixelements and astrophysical S-factorsfor radiative capture processes can be extracted fromexperiments. We describe the basic theory, new re-sults concerning higher order effects in the dissocia-tion of neutron halo nuclei . Some new applicationsof Coulomb dissociation for nuclear astrophysics andnuclear structure physics are discussed.With increasing beam energy higher lying statescan be excited with the Coulomb excitation mech-anism. This can lead to Coulomb dissociation, inaddition to Coulomb excitation of particle boundstates . Such investigations are also well suited forsecondary(radioactive) beams. Due to the time-dependent electromagnetic field the projectile is ex-cited to a bound or continuum state, which can sub-sequently decay. If l" order electromagnetic excita-tion is the dominant effect, experiments can directlybe interpreted in terms of electromagnetic matrix-elements, which also enter e.g . in radiative capturecross-sections The question of higher order effects istherefore very important. We present new results fora simple and realistic model for Coulomb dissociationof neutron halo nuclei . We show that these effectsare reassuringly small. Results from [4] are shownin Fig.l . We also discuss new possibilities, like the

1.2

1.0

0.8a 0.6

ä 0.4b

0.2

0.0.0 0.5 1.0 1.5 2.0 2.5 3.0

E,, [MeV]

Figure 1: Differential cross sections integrated overscattering angle from 0° to 3° for the Coulombdissociation of 67 MeV/u 19C scattered on 20sPbas a function of the relative energy. Analyticalmodel with finite ~-correction : LO-calculation (solidline), LO+NLO-calculation (dashed line); semiclas-sical calculation : El first order (dotted line), E1 dy-namical (dot-dashed line); experimental data from[5) .

experimental study of two-particle capture .Electromagnetic excitation is also used at relativis-tic heavy ion accelerators to obtain nuclear structureinformation. Recent examples are the nuclear fis-sion studies of radioactive nuclei and photofission of"'Pb . Cross-sections for the excitation of the giantdipole resonance ("Weizsäcker-Williams process") at

132

the forthcoming relativistic heavy ion colliders RHICand LHC(Pb-Pb) at CERN are huge , of the orderof 100 b for heavy systems (Au-Au or Pb-Pb) . Incolliders, the effect is considered to be mainly a nui-sance, the excited particles are lost from the beam .On the other hand, the effect will also be useful as aluminosity monitor by detecting the neutrons in theforward direction .Peripheral collisions of medium and high energy nu-clei (stable or radioactive) passing each other atdistances beyond nuclear contact and thus domi-nated by electromagnetic interactions are importanttools of nuclear physics research . The intense sourceof quasi-real (or equivalent) photons has opened awide horizon ofrelated problems and new experimen-tal possibilities especially for the present and forth-coming radioactive beam facilities to investigate ef-ficiently photo-interactions with nuclei (single- andmultiphoton excitations and electromagnetic disso-ciation) .References :

[1) G.Baur,S .Type1,H.H.Wolter,K.Hencken,andDJrautmann, proceedings of the RCNP-TMUSYMPOSIUM on Spins in Nuclear and HadronicReactions , October 26-28 1999, World Scien-tific Publishing Company, (2000)p.119 edited byH.Yabu, T . Suzuki, and H. Toki, see also nucl-th/0001045

[2] G.Baur, K.Hencken, D.Trautmann, S.Typel,and H.H.Wolter nucl-th/008033 to be publishedin the proceedings of the NATO Advanced StudyInstitute "Nuclei Far From Stability and Astro-physics" Predeal, Rumania 28.8.-8.9.2000,KluwerAcademic Publishers

[3) G.Baur, K.Hencken, D.Trautmann S .Typel andH.H.Wolter, nucl-th/0011061, to be published inthe Proceedings of the International Workshopon Nuclear Physics, Brice 16 .24.9 .2000,Progressin Particle and Nuclear Physics Vol-46

(4) S .Typel and G.Baur, nucl-th/0101033, submit-ted to Phys .Rev C

[5] T.Nakamura et al . Phys.Rev .Lett. 83(1999)1112

* NSCL,MSU,East Lansing** Sektion Physik, Universität München, D-85748Garching, Germany***Institut für Theoretische Physik, UniversitätBasel,Klingelbergstraße 82, CH-4056 Basel, Switzerland

In central collisions at relativistic heavy ion col-liders like RHIC at Brookhaven and LHC atCERN/Geneva one aims at producing and detect-ing a new form of hadronic matter, the Quark GluonPlasma . In [1] a complementary aspect of these col-lisions was discussed : the very peripheral ones . Dueto coherence there are strong electromagnetic fieldsof short duration in such collisions . They give riseto photon-photon and photon-hadron collisions upto invariant mass regions hitherto unexplored ex-perimentally. Together with the experimentalists S.Sadovsky andYu. Kharlov a review is being preparedfor Physics Reports [2] to discuss these questions .The Relativistic Heavy Ion Collider RHIC is now inoperation in Brookhaven . A dedicated program ex-ists to study these peripheral collisions [3] . A the-oretical review was given at PHOTON 99 [4] . Theaspects of very peripheral collisions at RHIC withfirst experimental results was recently reviewed in

It was suggested to use the CMS detector at LHC forphoton-photon physics at LHC [6, 7] . Some aspectsof this were also discussed in connection with theLetter of Intent for FELIX [8] .These relativistic heavy ion colliders may also servewell as vector meson factories [9, 1, 5] . At RHIC theinvariant mass region is similar to the one at HERA.A new energy regime will be entered at LHC. InFig. 1 we show the expected rate for vector mesonproduction for Pb-p collisions (the Pb ion providesthe large photon flux) . In AA collisions we have co-herent as well as incoherent vector meson production .In the incoherent case there will be a scaling with A"where the exponent a N 0.9, to take shadowing intoaccount . In the coherent case, the scaling will varyfrom a = 2/3 (black nucleus, relevant for the lightermesons) to a = 4/3 (transparent nucleus, relevantfor the heavier ones J/0 and T) .Production of low mass electron pairs due to thephoton-photon mechanism in central collisions wasrecently studied theoretically in [10] .

References:

Photon-Photon and Photon-Hadron Physics in Very Peripheral Relativistic Heavy IonCollisions

G . Bau1, K. Hencken, and D. Trautmann, Top-ical Review, J. Phys . G 24, 1657 (l998) .

G . Baur,K .Hencken, D.Trautmann, S .Sadovskyand Yu .Kharlov, Phys . Rep. in preparation,(deadline August 2001) .

Star Peripheral Collision group, see, e.g ., athttp ://www .star . bnl .gov/STAR/html/pec1/base .html.

K. Hencken, P. Stagnoli, D . Trautmann, and G .Baur, Nucl . Phys . B 82, 409 (2000) .

G . Bau1, K . Hencken*, and D. Trautmann*

133

10-2

10-4Chw

1o-6

10-8äb

10 -10

10-12

Figure 1 : The cross section and production rates forthe total hadronic production as well as vector mesonproduction are shown for Pb-p collisions at the LHC(L = 10 26cm-2S-1) . Estimates for the cross section'of coherent and incoherent vector meson productionin AA (Pb-Pb) collisions can be obtained by scal-ing with an appropriate power of A . M denotes theinvariant mass of the -1p system .

S . R. Klein, Nonlinear QED Effects in HeavyIon Collisions, LBNL-47144,physics/0012021

[6] G. Baur et al., Photon-Photon Physics withheavy ions at CMS, CMS Note 1998/009,available from the CMS information server athttp://cmsserver .cern.ch, 1998 .

G . Baur et al., Heavy Ion Physics Programmein CMS, CMS NOTE 2000/060, 2000 .G. Baur, in CMS Heavy Ion Meeting in St. Pe-tersburg Junell-14,2000 , edited by M. Bedjid-ian (2000), p. 207 .K . Hencken, in CMS Heavy Ion Meeting in St.Petersburg, edited by M. Bedjidian (2000), p .219.CMS Document 2000-030

K . Eggert et al., FELIX Letter of Intent,LERN/LHCC 97-45, LHCC/I10, to appear inJ. Phys . G (2001) .

S . Klein and J. Nystrand, Phys . Rev. C 60,014903 (1999) .

[10]

K. Hencken, D. Trautmann, and G. Baur, Phys .Rev. C 61, 027901 (2000) .

*Institut für Theoretische Physik, Universität Basel,Klingelbergstrasse 82, CH 4056 Basel, Schweiz

C

a=B+Alogy.

0 10 20

Bound-Rree Pair Production in Relativistic Heavy Ion Collisions

H. Meier*, Z. Halabuka*, K. Hencken*, D. Trautmann*, and G. Baur

This work is published in [1] . We study the electron-positron pair production with electron capture to theK- and higher shells with quantum numbers njlm inrelativistic heavy ion collisions . For a general refer-ence see [9] . The bound-free pair production in thecollision of two charged particles has found an appli-cation in the production of relativistic antihydrogen[4] . The corresponding process is very important atthe relativistic heavy ion colliders RHIC and LHC.Due to the change of the charge to mass ratio in thecapture process

Z + Z -+ Z + (Z + e- )n j lm + e+

( 1 )

the ions will be lost in the circulating beam and theluminosity will be seriously affected . Furthermore,due to localized beam pipe heating, there is a dan-ger of a quenching of the superconducting magnets[2], which is especially serious for the Pb-Pb colli-sions at LHC [3] It is important to know the crosssection very accurately . In [5] and [6] the bound-freepair production leading to relativistic antihydrogenwas calculated in the PWBA. Whereas in the latterreference lepton wave-functions appropriate for thelow values of Z (= +1 and -1)were used, we usenow [1, 8] exact Dirac wave functions.They are alsovalid for the higher Z-values of the relativistic heavyions . The methods of [6] are also applied to the heavyion case in [7]. We find that the cross section can bewritten as

In Fig. 1 we show the dependence of the diferent crosssections on the ion charge Z . As the cross section forthe s states is proportional to Z7 for low values ofZ we divide by this factor . For further details see

30 40 50 60 70 80 90Z

Figure 1 : The cross section for electron capture intodifferent bound states is given as a function of thecharge Z of the ion. A Lorentz factor of y=3400 inthe collider frame is used .

[1] . There is an 1/n3 scaling law for the s-states .Transitions to p states is strongly supressed . Due tothe s-character of the small component of the pl/2

134

wave function, it is enhanced as compared to thep3/2 wave function .

References :

[2] S .R . Klein physics/0005032 to be published inNuclear instruments and Methods

H.Meier, Z.Halabuka,K .Hencken, D.Trautmannand G.Baur, Phys.Rev .A, in print, nucl-th/0008020

CMS document 2000-030, p .295 D.Brandt talkgiven at the CMS Heavy Ion Meeting inSt .Petersburg, Junell-14,2000

[4]

PS21 collaboration, W. Oelert, spokesperson, G.Baur et al ., Phys . Lett . B368 (1996) 251 .

[6] C . A. Bertulani and G. Baur, Phys . Rev. D58(1998) 034005 .

[8] H. A. Bethe and E. E. Salpeter, Quantum Me-chanics of One- and Two-Electron Atoms, 1977,Plenum Publishing Corporation, New York .

H. Meier, Z. Halabuka, K. Hencken, D . Traut-mann, and G . Baur, Eur. Phys. J . C5 (1998)287, see also hep-ph/9712461 .

C.A . Bertulani and D.Dolci Nucl.Phys. A inprint, nucl-th/0008015

G. Baur, K . Hencken, and D . Trautmann, Top-ical Review, J . Phys . G24 (1998)1657 .

*Institut für Theoretische Physik Universitaet Basel,Klingelbergstrasse 82 CH4056Basel Schweiz

10-9 ls1122s 112

10'10 3s 1n c2p1n °

10"11 2p312 r

1042 } .. . . . ... . . --------..ß . . . . . ....... . . .:- . :.4 .

10"13

10-14 7

10-15 1 i ., .

where

Pionium interacting with matter

T.A . Heim*, K. Hencken*, M. Schumann*, D . Trautmann*, and G. Baur

We present results of a detailed investigation ofthe target-elastic and target-inelastic electromag-netic cross sections for pionium scattering off vari-ous target materials . Further details can be found in[1] and [2] . Accurate predictions for this quantity areneeded as a theoretical input in the analysis of theongoing DIRAC experiment at CERN [3] . This ex-periment aims at measuring the pionium lifetime, animportant check on chiral perturbation theory [3].To describe the excitation of the pionium atomsthrough the electromagnetic interaction with thetarget atoms we use the semi-classical approxima-tion (SCA). In the rest-frame of the pionium, themuch heavier target atoms move past with almostthe speed of light on a straight-line trajectory R ={b, 0, vt} and are treated classically, whereas the pio-nium atom is situated at the origin of the coordinatesystem and is treated quantum-mechanically .The non-relativistic Hamiltonian describing this sys-tem is

H = Ho -f- Hint ,

(1)

where the first part, Ho, describes the pionium atom,

Ho = p2

e2

(2)2 - r ~

where I.L is the reduced mass and r" the relative coor-dinate . The second term in (1), Hint , describes theinteraction between the pionium and the target atom

For the calculation of the higher order correctionsonly Hscalar will be considered, as it yields the maincontribution to the cross-section . The effect of themagnetic interaction Hmag (and of relativistic cor-rections) are found to be much smaller than 1% [4] .The transition amplitude afi (b) from an initial statei = {ni, li, mi} to a final state f = {nf, lf, mf},where n, l, and m denote the principal, angular, andmagnetic quantum numbers, respectively, is given inthe sudden (orGlauber) approximation by

afi (b)=fd3r0f (r

[1 - exp (iX(b, rl)] iki (r1, (5)

X(b, rJ _ -

ooHint (b, T, t)dtf .

One can easily check that the term linear in X inthe expansion of the Glauber cross section yields thefirst-order (Born) cross-section [5] where the energydifference w is neglected, which is, in fact, one of the

135

References :

b [a�1

Figure 1: Comparison of the the breakup probabili-ties for the transition 1s-2p of the pionium due to theCoulomb interaction with a Nickel (Z=28)atom . Theslow convergence of 27rb I afi (b) 12 (solid line) is clearlyvisible, whereas the higher order terms (differencebetween first order (Born) and Glauber approxima-tion, dotted line) are limited to small b . Also shownis the relative difference between the probabilities infirst order with and without a finite w. Whereas thisdifference increases with b, it is small in the area of b,where the higher order terms contribute appreciably .

approximations made in Glauber theory (the suddenapproximation) .The results for the breakup probabilities are shownin Fig. 1 as a function of the impact parameter b. Theapplicability of the Glauber theory is also tested byshowing the difference of the first order results withand without taking the finite value ofw into account.The importance of higher order corrections increasesrapidly with the charge number Z. For heavy nucleithey can be as large as 20% of the Born result . Thiswork is in progress .

[1] T. Heim, K. Hencken, D. Trautmann, andG. Baur, J. Phys . B 33 (2000) 3583 .

[2] HadAtom99 Workshop on Hadronic Atoms Oc-tober 14-15,1999, Bern, Switzerland, available ashep-ph/9901381 .

[3] see the homepage of the DIRAC experiment atHTTP ://WWW.CERN.CH/DIRAC/ .

[4] T.A . Heim, K. Hencken, D. Trautmann, andG. Baur, work in progress (2001) .

[5]

Z. Halabuka, T.A . Helm, K. Hencken, D . Traut-mann, and R.D . Viollier, Nucl. Phys . B 554(1999) 86 .

* Institut für Theoretische Physik, Universität Basel,Klingelbergstrasse 82, CH-4056 Basel, Switzerland

Hint = Hscalar -I- Hmag , (3)

where the scalar interaction is given by

Hscalar = e [,D(r/2) - -1)(-r/2)] . (4)

The fundamental feature of the time-evolution of self-organizing complex dynamical systems, such as financialmarkets, is a permanent coexistence and competitionbetween noise and collectivity . Noise is ubiquitous andoverwhelming, and therefore it seems natural that majorityof eigenvalues of the stock market correlation matrix agreevery well [1] with the universal predictions of randommatrix theory [2] . Collectivity on the other hand is muchmore subtle but it is this component which is of principalinterest because it accounts for system-specific non-randomproperties and thus potentially encodes the system's futurestates.Previous works [3] are based on the studies of the singlestock markets, in isolation to all the others . An every dayexperience indicates, however, an increasing role of effectsconnected with the world globalisation, which seems also toaffect the financial markets . It is therefore of great interestto quantify the related characteristics . On a way towardsexploring this issue we study the cross-correlations betweenall the stocks comprised by DAX and by Dow Jones . Bothinclude the same number (30) of the companies and inspace terms represent two distant and at the same timeleading markets in their area. Mixing them up results in 60companies which determines the size of the correlationmatrix to be studied.

Fig. I

ElotmalNieorc ',*,Adon l iablx:(boeMAX andO"Jön .nj

Cross-correlations in the stock market: DAX versus Dow Jones

S . Dro2dz, F . Grümmer, F. Ruf and J . Speth

~or~Dnxj

The time-dependence of the six largest eigenvalues versusthe corresponding two indices (DAX and DJ) is illustratedin Fig . 1 . In contrast to a single stock market case, wheredynamics is typically dominated by one outlyingeigenvalue, here one can systematically identify two largeeigenvalues . The range of variation of the remainingeigenvalues is on average compatible with the limitsprescribed [4] by entirely random correlations . In fact thetwo largest eigenvalues represent the two stock markets as ifthey were largely independent.From the technical perspective reconciling these somewhatconflicting conclusions turns out more straightforward thanexpected and at the same time leads to a new veryinteresting result . By constructing the correlation matrixwith the DAX returns are taken one day advanced relativeto the Dow Jones returns, one obtains the eigenspectrum

136

whose structure significantly changes. Its resulting time-dependence is shown in Fig. 2. Now, except for the early90's, one large eigenvalue dominates the dynamics whichmeans that a sort of a one common market emerges .Consistently, it also obeys the characteristics observedbefore [3] for the single markets : as a rule the collectivity ofthe dynamics is weaker during increases than duringdecreases.

Fig.2

In summary, the present study of the time-dependence ofcross-correlations between all the stocks comprised byDAX and by Dow Jones points to a significant novelelement associated with dynamics of the contemporaryfinancial evolution . By properly taking into account thetime-zone delays both these markets largely merge into asingle one . This becomes particularly spectacular in the lastfew years . At the same time an emerging global marketpreserves the distinct difference in the mechanismgoverning increases and decreases, respectively . Similarlyas for single markets [3] the increases also in this case areless collective and more competitive than decreases . Thisstudy also documents that it is the Dow Jones which takes aleading role in this emerging global market. As aninteresting problem for further study it seems likely thatsuch a global world market involves many other markets aswell .

References[1] L. Laloux, P . Cizeau, J-.P Bouchaud and M. Potters,Phys . Rev . Lett. 83, (1999) 1467[2] M.L. Mehta, Random Matrices (Academic Press,Boston, 1999)[3] S . Drotdz, F . Grümmer, A. G6rski, F. Ruf and J . Speth,Physica A287, (2000) 440[4] A. Edelman, SIAM J. Matrix Anal . Appl . 9, (1988) 543

On the Electric Field of Homogeneosly Charged Ellipsoids .

While the charged ellipsoidal conductor as well as thedielectric ellipsoid are discussed in textbooks of clas-sical electrodynamics, eg . in [1], this does not seemto be true for the homegenously charged ellipsoid . Infact, this problem has been beautifully as well as gen-erally discussed in an old monograph [2], but eventhere the special case of rotationally symmetric ellip-soids is not discussed in detail, in spite of the fact thatonly this allows a solution in closed analytic form .We define a rotationally symmetric prolate ellipsoidby its halfaxes c in z-direction and a in radial direc-tion (with c > a) and the excentricity l = c -a2 .Families of confocal ellipsoids and hyperboloids canthen be written as

u2 u2-1 ' v2 1-v2 'where u and v are elliptical coordinates [3], which arerunning from 1 to oo and -1 to +1, respectively. Thecylindrical coordinates z and p can be expressed bythese through the eqations

z = uvl,

P2 = (u2-1)(1-v2)l2 .

(2)Inside the ellipsoid the constant charge density r. gen-erates a potential that has to follow POISSON'S equa-tion V2 V = -rs. It can easily be seen that the solutionmust have the form

Vin(P,Z)

-- Z2-2+C,where C is a constant and y a yet undetermined pa-rameter that depends on the ratio c/a.Outside the ellipsoid we look for a rotationally sym-metric solution of the LAPLACE equation V2V = 0that depends only on the coordinats z andpor, prefer-ably, on the elliptic coordinates u and v. We get thedifferential equation

T(u2-1) 8u +8v (1-v2) öv .In analogy to the solutions of the SCHRÖDINGER equa-tion we find V(u, v) = f(u)g(v), where f(u) as well asg(v) follow the differential equation

dx2 dxThe separation constant D can be shown to be re-stricted to angular-momentum-like quantum numbersv(v+1) with v = 0,1,2, . . . . So we get two sets of su-lutions, the LEGENDRE functions of the first and thesecond kind [3],

9(v) = P�(v)

and

f(u) = Q,(u) .

(6)

We can use eqs. (2) and this result to rewrite eq . (3) :

'Vin(u'�) =-6(1+2y) Lu2+2y(u2-1)

+2(u2-y(u2-1))P2(v)] +C

V. Klemt

Now our problem can be solved by parametrizing theexterior solution in the form

Vex(u, v) = AQo(u)+BQ2(u)P2(v) ,with

Q2 (U) =3u

2-1

3uQ0(u)--

1Qo(u) = 2 In

U-1'

2

2

and

P2(v) = 3vz-1 .2

In fact, the monopole and quadrupole terms in eq . (8)show the right asymptotic behavior for u -+ oo,

QO(u) -

+C(ü)'

Q2(u) - 15U3 +C \us/'and, in addition, we have four continuity conditionson the surface . The logarithmic derivative of themonopole term determines A, that of the quadrupoleterm y. Finally, the values of the constants C andB follow from the continuity of the monopole andquadrupole parts of the potential itself. We get

A

with uo = c/l and the total charge q = 47ra2cr./3.It is interesting to look at y as a function of the defor-mation parameter A = c2 /a2. After some calculationwe get the two limiting cases

),3/5

and

y(A) -

aIn4a

for small (A = 1+s with e -4 0) and large (A -4 oo)deformations, respectively.For y = A the equipotential surfaces would have thesame c/a-ratio as the ellipsoid itself. In reality, wefind ellipsoids whose eccentricity is reduced.

It remains to be mentioned that there is another lim-iting case of a triaxial ellipsoid, the uniformly chargedelliptical cylinder . Its study is of some practical im-portance in accelerator physics [4], and an analyticalsolution for the interior of the cylinder is known fromthe literature [5] . Also in this case the method out-lined above is suitable for getting a complete analyti-cal solution .

[1] L. D. Landau, E. M. Lifshitz, Electrodynamics ofContinuous Media, Pergamon Press 1970 .

[2] 0. D. Kellogg, Foundations of Potential Theory,Frederick Ungar Publ . Co., New York 1929 .

[3] M. Abramowitz, I. Stegun, Handbook of Mathe-matical Functions, Dover, New York 1964 (Chap-ters 21 and 8) .

[4] H. J . Stein, private communication .[5] L. C. Teng, ANLAD-59 .1960 .

-B 4I1 ' C 8nl Qo (uo)

uo [uo - (uö -1) Qo (uo)](10)

y 2(uö-1) [u0Qo(uo) - 1]

138

III .

Accelerator Division

5. COOLER SYNCHROTRON COSY

6. ION SOURCES AND BEAMTRANSPORT

7. SPECTROMETER BIG KARL

8. RADIATION PROTECTION

5. COOLER SYNCHROTRON COSY

Beam Time Statistics

With 7776 scheduled hours, of which 7457.5 were de-livered, the reliability of all components of COSY wasagain illustrated . 82.7 % of the planned beamtime wasused by experiments, the fraction of experimentalbeamtime with polarized protons being over 1/3 . Sig-nificant improvements can be reported in the conserva-tion of the beam polarization during acceleration, aswell as in an increase of the intensity of the polarizedbeam. The polarized source not only delivered higherintensities but also demonstrated a substantially im-proved reliability .

Acceleration ofDeuterons

Some experiments proposed for COSY are going to usedeuteron beams. To realize this in COSY, the extrac-tion septum of the cyclotron was replaced with a newseptum which can hold the voltage necessary for theextraction of deuteron ions at 76 MeV kinetic energy(momentum = 540 MeV/c) . After installation of theseptum first tests for the preparation of D--beams in theion source and acceleration in the cyclotron were car-ried out. These tests were very successful and a cur-rent of 8 g.A D- was extracted from the cyclotron. In aone day machine development period, the D--ions werestrip injected into COSY, stored as D+ and acceleratedto a momentum of 3 GeV/c. The tests show, thatCOSY is capable of delivering deuteron beams of thesame intensity and quality as in the case of protons .The polarized proton source for COSY is also suitedfor the preparation of polarized deuteron ions . There-fore experiments with polarized deuterons will be pos-sible in the future .

Crossing Transition Energy at COSY with a fast PhaseJump

In a synchrotron the revolution frequency of a particlewith a given energy is determined by the ratio of its ve-locity and mean orbit radius . If, at constant magneticfields, the energy is slightly increased, then both veloc-ity and orbit radius will increase . The change in revolu-tion frequency depends on whether the relative velocitychange is greater than the orbit change or not. For lowenergies the relative velocity change dominates and therevolution frequency increases with increasing energy .At relativistic particle energies the orbit change domi-nates and the revolution frequency decreases when theenergy is raised . That is, a more energetic particleneeds a longer time to complete one turn in the syn-chrotron . Somewhere in between there is an energy,called transition energy or for short transition, at whichthe relative velocity change just compensates the rela-tive orbit change. Particles with slightly different ener-gies now have all the same revolution frequency. Therelative orbit change also depends on the horizontal fo-cusing of the machine : The stronger the focusing thehigher is the transition energy . Ifthe transition energy

Operating Report of COSY in 2000U. Bechstedt, J. Dietrich, B. Lorentz, R. Maier, D.Prasuhn,A.Schnase, H. Schneider, R.Stassen, H.Stockhorst, R.T611e

lies in the covered energy range, as is the case formany proton machines, special care has to be taken toaccelerate the beam to maximum energy . Consider areal beam possessing an energy or momentum distribu-tion . A particle with mean momentum circulates on amean orbit (reference particle) . It stays on the mean or-bit during acceleration if the relative field increaseequals the relative momentum increase determined bythe radio-frequency . In the linear ramp of COSY thereference particle then experiences the same rf-phase(synchronous phase) $S resulting in the constant en-ergy gain VO sin(~S) from turn to turn . Below transi-tion the synchronous phase must lie on the positiveslope of the rf-voltage wave. With respect to the refer-ence particle (A), particles (B) lagging behind gainmore energy and arrive earlier at the cavity in the nextturn while those arriving earlier (C) are slowed down(Fig . 1). Thus, particles with small energy deviationswith respect to the reference particle execute stable os-cillations around the synchronous phase . Their projec-tion onto the phase (time) axis yields the stable particlebunch that is accelerated.

stable phasebelovtransttion

stable phsaeabovetrarpironRFVdtaae

jRFYdtape .

Fig . 1 : Below transition energy the phase of the bunchwith respect to the radio frequency is set on the posi-tive slope ofrf-wave for a stable motion . Above transi-tion energy the phase must be switched to the negativeslope. The double arrows indicate the stable oscillationaround the synchronous particle

No stable oscillation below transition is possible if thesynchronous phase is chosen on the negative slope ofthe rf-wave . The bunch will dilute in phase extent aswell as momentum spread and will be lost. On the con-trary, above transition a stable motion is only possiblewhen the synchronous phase lies on the negative slopeof the rf-voltage wave. For the same energy gain as be-low transition the phase must be set to 7c - OS . Close totransition the bunch becomes very short and the mo-mentum spread very large so that eventually the ma-chine aperture is exceeded. More important, in the vi-cinity of transition intense beams are rather sensitive tospace charge forces leading to a fast emittance blow upin both, transverse and longitudinal phase space. Evenright after transition space charge may be still danger-ous for a period of time because now these spacecharge forces support the focussing forces of the radiofrequency . Any density disturbance within the bunch isnow enhanced resulting in high frequency bunchingwhich may act back on the beam via the impedance ofthe beam pipe. To avoid these problems the transition

energy is generally shifted upwards during accelerationin COSY. Unfortunately, the highest possible sym-metry of the lattice which is of great advantage for po-larized beams (COSY NEWS No. 8) is reduced by thismeasure. A high symmetry of the machine during ac-celeration is only possible if the transition energy iskept fixed at about 1.5 GeV/c. Consequently, this op-erational mode is only interesting for external or thoseinternal experiments that take data sufficiently faraway from transition . First experiments to cross transi-tion energy solely with a fast phase jump were carriedout .

Fig. 2: Transition crossing solely with a phase jumpduring acceleration to 2.027 GeV/c .

Fig. 2 shows a bunch with 2101° protons during ac-celeration to 2.03 GeV/c in the vicinity to transition .Starting below transition 100 bunch profiles were takenconsecutively every 2.5 ms . The bunch with 100 nswidth becomes narrower and the bunch height in-creases when transition is approached. Close to transi-tion the acceleration phase was jumped from 30 to 165degrees within 1 ms . During crossing 15% loss of par-ticles occurred . Bunch oscillations and bunch dilutionwere kept to a minimum by closing the phase controlloop well before transition . After crossing transition at1 .5 GeV/c the beam is again stable.

Fast Extraction for ESS-Target Research at COSY

Since 1993 the research program at COSY with inter-nal as well as external experiments is underway . Forexternal experiments the accelerated beam is extractedout of COSY and led through external beam lines tothe location of the experiment. Stochastic extraction isapplied to extract the stored beam over spill periods upto several minutes with an almost constant flux inmean .

For the European Spallation Source (ESS) target re-search project JESSICA it is necessary to extract thecomplete COSY beam in less than 10-6 s to reach veryhigh flux at the external target location . Since the sto-chastic extraction is not intended for short spills a newextraction method, the fast kicker extraction, was re-cently developed and successfully applied to extractthe beam. For kicker extraction, the stored beam isguided into the extraction septum by means of a fastkicker magnet. Because of space constraints it was notpossible to accommodate a new magnet for this pur-pose, however an already existing kicker magnet wasavailable . First tests showed that this magnet, installedfor beam diagnostics and therefore limited in strength,

is not sufficiently strong to extract the COSY beam be-ing prepared and accelerated in the standard mode ofthe accelerator at higher energies . At lower energies108 protons in pulses of less than 10-6 s could be ex-tracted, but with the standard settings of the acceleratorthe beam dimensions at the location of the extractionseptum were too large to reach higher intensities .

After the feasibility of the method was shown in thesefirst tests a special machine setting with reduced beamdimensions at the extraction septum was developed .The high flexibility of the machine made it possible tochange the orbit in such a way that the beam position atthe location of the extraction septum was put veryclose to the septum such that the strength of the kickermagnet is sufficient to move the beam into the septum.In addition electron cooling at injection energy was ap-plied, which reduces the beam dimension by roughly afactor 5 .

With this special beam preparation it was possible toextract 109 protons in pulses of a few 100 ns length anda repetition rate of 10 Hz at the energy 1.3 GeV fore-seen for the ESS. For diagnostics in the extractionbeam line, a wall current monitor was applied. Thepassing protons induce an image current in the beampipe that is measured through resistors over a ceramicgap in the beam pipe (see Fig . 3) .

Polarized Proton Beam

Vamm

iV 'C

*-

606.0 ~,9 .t V SP7

666 R6/h50 nV ~

1-

Z OC 6.9äV

09l~I~fi6C0

Fig . 3 : Measurement of the time structure of the protonpulse in the extraction beam line with an intensity2.109 protons .

Last year we reported in detail about the methods ap-plied to overcome depolarizing resonances without lossof polarization during acceleration of polarized protonbeams in COSY. At imperfection resonances the reso-nance strength is increased by means of vertical steer-ing such that the polarization of the beam is flippedwhen crossing the resonance . For intrinsic resonances,which depend on the vertical tune in the accelerator,fast quadrupole magnets are used to jump quicklyacross the resonance tune. As a result the polarizationis preserved . In the year 2000 this method could be sig-nificantly improved. It was possible to keep the polari-sation at a value of 0.76 at 3.3 GeV/c, which meansnegligible polarization losses (5 % out of 0.8) duringthe whole acceleration (Fig . 4). The measurement ofthe absolute value of the polarization during accelera-tion was accomplished by measurements of pp elasticscattering using the EDDA detector . At this point we

like to express our gratitude to the EDDA collaborationfor their indispensable assistance.

Fig. 4 : Polarization versus momentum during accelera-tion as measured with the EDDA detector.

In the meantime polarized beam with a high degree ofpolarization is not only used by internal experiment,but also by the external TOF experiment . Here the slowor stochastic extraction is used to extract the beamfrom COSY and guide it to the external experimentalarea . During slow extraction the energy of the storedbeam is held at a constant value for the whole extrac-tion time, which can be several minutes . Thus it is herealso important to avoid an energy close to depolarizingresonances . Even higher order resonances could lead toloss of polarization during the long extraction period .In 2000 during a TOF beam time, the extracted beampolarization as measured via pp elastic scattering bythe TOF collaboration reached a value of 0.8 or larger(Fig . 5) . With this it is demonstrated, that in COSY po-larized beam can be accelerated and extracted withouta significant loss in polarization and polarized beamcan be used by internal and external experiments.

0 .2

-0 .t

-0.x

-0.3

-0.4

-0.5

beam momentum (Mevle)

aptn (up-down)/(up+down)

Fig . 5 : Asymmetry of pp elastic scattering as measuredwith the TOF detector. The asymmetry corresponds toa beam polarization of 0.8 or larger .

Polarimeters for the internal and external COSY beam

F . Bauer*, N. Bongers, C . Deliege, F.-J . Etzkorn, R . Gebel, B. Lorentz, P. v . Rossen, A. Schnase, H. Stockhorst, R . T61le

Up to now polarisation development in COSY depended onthe availability of the EDDA detector which was used as ahighly effective internal polarimeter. On the other hand thisdetector with its appr. 1000 channels is too complex forevery day use and the EDDA staffmay not be available atevery time . Thus in collaboration with the University ofHamburg a polarimeter was developed [1,2,3], which canbe used for the internal beam during acceleration as well asat flat top energy. A smaller version of the polarimeter isused in the extraction beamline .

Fig. 1: Geometry of the scintillators ofthe internal polarimeterThe trajectory angle of the hit protons varies with beammomentum. Arrows indicate the directions for the (in CMS)forward scattered proton andfor the backward scattered proton,resp . By coincidence mainly elastic collisions are counted.

The internal polarimeter, as shown in fig . 1, is equippedwith 18 scintillation detectors. A similar polarimeter isavailable in the extraction beamline.The backward detection system is identical for internal andexternal polarimeter. The external polarimeter is equippedwith only one forward telescope on each side of the beampipe . Before the measurement, the position of the forwarddetector is adjusted to match the pp elastic scattering anglesat extraction energy. The internal polarimeter uses twoforward telescopes at different angles to be able to recordpp elastic scattering events over the whole energy range ofCOSY without a change ofthe detector positions . The dataacquisition software and electronics are the same for bothpolarimeters . It records both protons ofpp elastic scatteringevents from the target in coincidence between forward andbackward detectors on opposite sides of the beam. Tocorrect for possible instrumental asymmetries the - softwarecalculates the pp elastic asymmetry by averaging overmeasurements with opposite beam polarisation . It displayshistograms of asymmetry vs . time and is thus well suitedfor internal measurements both during acceleration and flattop, and for external measurements .At present the signals of only one polarimeter areconnected to the electronics to avoid large area groundloops. Automatic switching is in preparation.After injection the target ofthe internal polarimeter (a 7gmCH2 fibre) is moved into the beam . The lifetime of thecirculating beam is typically a few hundred msec. Duringthat time the elastically scattered protons are counted .Afterwards the target is moved out of the beam. Fig . 2shows the acquired spectrum after 5 min measuring time .The asymmetry is in the order of -30 % at 1.4 GeV/c, Thedigital motor control had to be replaced by a fully analogue

146

design with operational amplifiers because after a defect noreplacement of the controller board was possible .For the same momentum (1 .4 GeV/c) COSY was switchedto extraction mode and the asymmetry in the extractionbeamline was recorded. A 5 mm polyethylene target is usedat this position which remains in the beam until the end ofthe measurement . Fig . 3 shows the result after 8 minmeasuring time . Again the resulting asymmetry is about -30 %.The effective analyzing power of both polarimeters as afunction of energy still has to be determined.

y

Fig. 2: Proton asymmetry @ 1400 MeY/c, internal beam,acquisition time app. S min.

asymmatr

0 .5

y 0 .0

-0.5

0.0

-0.5

1000 1500 2000 2500 3000asym.Ohlsen T2* time [ms]

-1 .04000 4500 5000 5500 6000

asym.Ohlsen T1

References[1] Thesis Karsten Büsser, Univ . Hamburg, 1999[2] Diploma Eike Jonas, Univ . Hamburg, 1999[3] Diploma Frank Bauer, Univ. Hamburg, 1998

*I . Inst . für Experimentalphysik, Univ . ofHamburg

time [ms]

Fig. 3: Proton asymmetry @ 1400 MeY/c, external beam,acquisition time app. 8 min. Asymmetry value of-30% is marked.

D7 - Beams from the Cyclotron JULIC forCOSY

W. Bräutigam, R. Brings,N. Gad, R Gebel, H. Hadamek, U. Rindfleisch

Since about 4 years the cyclotron JULIC is almostexclusively operated as H'-injector for the CoolerSynchrotron COSY which requires ions suitable for theinjection by stripping . In the first years of COSYoperation only HZ+ beams of 76 MeV were used for theinjection into the ring . Switching to . negative ionsbecame necessary after the ion source for polarizedparticles was available for full operation. Since thissystem has to deliver beams with high polarization andbrilliance, a colliding beam type source (CBS) waschosen, providing only negative particles. It is designedto deliver IT and D" ions within the acceptance of thecyclotron (0.5 7c-mm-mrad, ß"y-normalized) during the10. . .20 ms injection period of COSY. Additionally twoindependent sources for unpolarized IT and D' ion beamshave been installed to minimze losses of beamtime bymaintenance.So at the beginning of 1996 the operation of thecyclotron (and consequently the injection into theCOSY-ring) were completely changed to negative ions .Converting JULIC into a negative ion machine waspossible without extensive modification. But achievingthe best performance for this type of accelerator turnedout to be a challenge . - In case of IT ions the cyclotronis operated at 45 MeVwhich is the maximum energy forparticles with Q/A--1 . Especially in case ofpolarized ionsit is not easy to provide the desired beam intensity at theinjection of COSY. Improving the performance of theion source has to be supported by measures at thecyclotron. In case ofJULIC the total beam transmissionis strongly dependent on the transmission ratio of theseptum deflector. While a figure of up to 701/o wasnormal for HZ+ ion beams, not more than 40. . .45% havebeen achieved in case of H" beams. This is due to thefact, that JULIC was originally conceived as anaccelerator for deuterons and a particles with itsspecifications optimized for the maximum energy of 45MeV/A Hence the curvature of the septum deflectorwas optimized for particles with Q/A = 1/2 at the highend of the energy range, where saturation effects in themagnet have to be considered which is not the case forIT beams of 45 MeV. Providing a septum deflector withan adapted radius could solve the problem but is notpracticable for a number ofreasons.In the recent years there is an increasing demand fromthe experiments for deuteron beams at COSY. Inprinciple it should be possible to generate polarized aswell as unpolarized D' ion beam in the various sourcesand to accelerate and extract it at the cyclotron with anenergy close to maximum energy of 90 MeV. But asexpected the operation of the septum deflector withreverse voltage at a high level proved to be impossibledue to severe electrical strength problems (sparking and

dark currents). Since already operating the originalseptum for FT beams with reverse polarity but moderatevoltage had encountered significant problems due tofield emission anew septum deflector had to be designedand developed. The new device should simultaneouslymeet the requirements for IT and D7 ion beams. It is notpracticable to provide individual devices for the differentbeams because this would require breaking the vacuumfor replacement before the according beam time. Severaldays pumping down time are necessary to achieve apressure in the order of 5"10' mbar which is needed foracceptable small beam losses due to residual gasstripping. Additionally it turned out that operation ofany septum deflector with reverse polarity at highvoltages is extremely sensitive to pressure in the vacuumchamber .A new septum deflector should meet a number ofspecifications: The problem of requiring diffrend radiifor extracting Ir and D" ions with good transmissionshould be overcome by larger aperture (from 4 to 5mm). Maximum field strength of about 120 kV/cmrequired for extraction of D' at 90 MeV should beachieved . Septum foil capable of dissipating the totalinternal beam power. System has to fit into the givenspace ofonly 50 mm in vertical direction.

Fig. 1:

Simplified scheme of the septum deflector.High voltage electrode is supported by ceramicinsulators which are also used as tubes for thecooling fluid. Mgh voltage cable is installed in theright tube with Fluorinert FC77 used for insulation.Septum foil consisting oftungsten wires

Many iterative steps were necessary, to develop a newseptum deflector which meets our requirements . Testshad to be done during development under realisticconditions, i, e. in magnetic field at a vacuum pressure of2. . .3 - 10'7 mbar. For this purpose we made use of a testmagnet equipped with a vacuum chamber. Tests ofdifferent electrode materials revealed, that titanium wasthe best choice . Furthermore, the geometry of electrodeand septum support had to be optimized carefiilly .We started with the entrance edge ofthe septum formedby 0.02 mm thick stripes of tantalum while thesubsequent part (where the extracted beam is alreadyseparated from the internal beam) consists of a wedge ofsolid titanium. In this configuration and a voltage appliedfor negative ions a field strength of about 120 kV/cmcould be obtained allowing to increase the radialaperture from 4 to 5 mm. After installation in thecyclotron, first tests with IT beam revealed animprovement of septum transmission from originally45% to > 65%. Unfortunately the tantalum stripes weredestroyed after a few days of operation. Probablyexcessive mechanical tension was the reason, that thestripes ruptured when they were heated up by the beam .We returned to a septum formed by a tungsten wirefence (wire diameter 0.2 mm, distance 0.2 nun) which isa significantly improved version of the septum operatedin JULIC since many years (Fig. 2)

Fig. 2: Septum for neative ions. Septum foil is formedby an upper and lower "fence" of tungsten wires.Precise shape and (indirect) cooling is achieved bytitanium supports .

The wires are manually inserted in Cu profiles withprecisely machined cuts made by electro erosion . Aslight deformation of the separating lip is sufficient tokeep the wires in plasc for the following productionsteps. With all wires inserted the profile surface is rolledto achieve a still better fixation together with a goodsurface quality. Then the profiles are brazed undervacuum for best possible heat conduction . Finally theyare inserted in watercooled titanium profiles whichdefine the precise shape. The upper and lower parts ofthe septum 'foil" are separated by a 0.5 mm zig-zagrunning gap (Fig . 2). This avoids any strain in the wires

due to misalignement or elongation when heated up bythe beam .The high voltage electrode is supported by ceramicinsulaturs made by a company according to ourspecifications . This devices turned out to be a source oftrouble when operated with reverse voltage. The alloyused for metal/ceramic joints produced severe sparkingresulting in a partly conductive coating of insulatingsurfaces . A number of attempts using different ways toachieve a working joint failed . Finally we developed amethod to make a vacuum tight joint between the A1203ceramic an titanium end caps without any additionalmaterial.The ceramic supports are also used as tubes for thecooling fluid Fluorinert FC77. I-Egh voltage cable isinstalled in the right tube (Fig . 1) with FC77 used forinsulation.

References :

Fig. 3 : First internal D' ion beam measured by the nonbeam disturbing phase detection systemupper trace: beam phase as a function ofradiuslower trace: beam intensity versus radius

Quite recently the system could be successfully testeddelivering D' beams of75 MeV with an extracted currentin the order of 10 pA. As appears from Fig. 3 theintensity ofthe internal beam is almost constant over theradius, indicating that vacuum pressure is not animportant limiting factor.

In the COSY ring about 1AEl1 deuterons could beinjected at a momentum of 538.4 MeV/c and thenaccelerated almost to the final momentum of 3 GeV/c.After acceleration about 4.5E10 Deuterons were storedin the ring during flat top period.

W. Bräutigam, R. Brings, R. Gebel, R. Maier, A.Schnase, "IT -Operation ofthe Cyclotron JULIC asinjector for the Cooler Synchrotron COSY-Jülich"Proc. 15th Int. Conf on Cyclotrons and theirApplications (Caen, France, 1998), pp . 654-657

A. Schnase, H. G. Böge, M. Böhnke, F.-J . Etzkorn, D . Ruhrig, S . Papureanu, H. Stockhorst

This year before spring, the broad-band cavity filled withtoroids made of VitroPerm instead of ferrites [1] was in-stalled in the COSY ring . The location of the cavity isshown in fig . 1 .

Fig . 1 : The place of the VitroPerm cavity in COSY.

With 80 cm length, this cavity is much smaller comparedto the (h=1) ferrite-filled cavity with its 210 cm length .The main advantage of this new cavity is the electricalbroadband transfer-function . It covers the frequency-rangeof COSY (500-1600 kHz) without any tuning and supportsthe simultaneous use of higher harmonics up to 8 MHz,enabling non-sinusoidal, periodic acceleration voltages .The ideas used for the signal synthesis will be also appliedto another broad-band cavity at KEK-PS [2] .By carefully selecting the ramping functions ofthe Fourier-coefficients for the signal synthesis, we obtain accelerationvoltages, which improve injection efficiency and alsoacceleration in COSY [3] . It is possible to increase thenumber of accelerated particles reaching flat top by about10% compared to acceleration with a sinusoidal voltageapplied to the beam with the conventional cavity . In theearly phase of experiments, it was sufficient to drive thecavity with 2 kW total RF power, delivered by 4 transistoramplifiers connected- to- 2 impedance transformers .

Fig . 2: The environment of the 50 kW tube amplifier

Experience with a VitroPerm cavity in COSY

148

To make full use of the advantages of this cavity, morepower is necessary . The tube amplifier build in the IKP forexperiments with another broadband cavity [4] was re-turned back to us from CERN. We modified the mechani-cal structure to match the VitroPerm filled cavity. Themain change is that the power tubes are not near the cavity- instead they are located outside the ring tunnel . They areconnected via 200 Ohms co-axial lines designed speciallyfor this purpose . A picture of the amplifier set-up is shownin fig . 2 .After the modifications of the tube amplifier were finished,we tested it with the main power delivered by the 10 kV,10A anode power supply of the ferrite cavity . This powersupply consists of two 3 phase transformers, rectifiers, andcapacitors . It is adjustable only in steps and as there is noregulation, we measure about 300V ripple. We do not wantto destroy good tubes, so by using old TH120 tubes withmore than 45000 hours of operation, we could demonstratethat the amplifier is again useable and that the safety inter-locks of the embedded Klöckner-Möller programmablelogic controller operate as expected. As the impedance ofthe cavity is a function of water quality, the cooling systemwas extended . Now the cavity is cooled by an independentheat exchanger'system .For everyday operation of the amplifier we will use a regu-lated 100 kW anode power-supply, built by the manufac-turer OCEM, Bologna . This supply delivers a voltage from0 to 10 kV at currents up to 10 A. It is primary regulatedwith thyristors. The maximum ripple of the output voltageat full load is less than 50 Vpp and contains the fre-quencies 100 Hz and 300 Hz. The internal crowbar pro-tects the power supply, the user and the amplifier from theenergy, which stored in the internal filter . A test with shortcircuit of the output where the current flows through a verythin copper wire will not destroy the wire, because thecrowbar absorbs the energy .This power supply is installed during the service periodstarting at the end of 2000 . In the beginning of 2001 theoperation of the amplifier and then of the cavity at higherpower will start . Then we can carefully increase theacceleration voltage at the cavity gap to find out about thelimits . Finally, we will check, if the ripple of the anodevoltage acts as an amplitude modulation of the gap signal .If this modulation is higher than expected, e.g . some voltsat accelerations voltages of some kilovolt, we will eitheradd an amplitude control loop, or we try to correct theripple by applying an anti-phase signal in the return line ofthe anode current .

References[1] A. Schnase et al ., " Preparing a Broadband Cavity forInstallation at COSY", IKP Annual Report 1999[2] M. Yoshii et . al ., " MA RF Cavity for the KEK 12 GEV PS",EPAC 2000, Wien[3] A . Schnase et al ., "Experience With a Broadband Cavity atCOSY", EPAC 2000, Wien[4] M. Crescenti et . al ., "The Vitrovac© Cavity for theTERA/PIMMS Medical Synchrotron", EPAC 2000, Wien

Magnets, Alignment and New Installations

U. Bechstedt, L . Conin, G. Dolfus, R . Enge, P. Faber, K. Jach, G . Krol, G . Langenberg, H. Pütz,B . Rogozik, D. Ruhrig, T . Sagefka, F . Scheiba

Like in 1999 there were no big new installations duringyear 2000 but a number of different activities .The external polarimeter built by the University ofHamburg was installed in the extraction beam line betweenthe multiwire proportional chambers 1.1 and 1 .2 . It isequipped with thick polyethylene and carbon targets toprovide for good statistics in a reasonable time that can bemoved into the beam by means ofpneumatic cylinders .Vacuum section 1 of the COSY-ring was rebuilt in twosteps . As first step the vertical schottky-pickup wasreplaced by a new rf-cavity that can be operated in higherharmonic modes to provide for nonsinusoidal accelerationvoltages .In a second step the residual gas beam profile monitor wasreplaced by a vacuum tube with a ceramic gap suppliedwith a new beam current transformer . This new transformerprovides higher resolution required by the TRI experiment .The residual gas beam profile monitor was rebuilt with ashorter vacuum chamber and installed in front of beamposition monitor 3 . The space required for this installationwas gained shortening the vacuum tube of BPM 3 as wellas the vacuum chamber inside bumper magnet 1 .After both the horizontal as well as the vertical schottky-pickups had been demounted from vacuum section 1, anewly designed schottky pickup was installed in vacuumsection 4 behind the internal polarimeter. This pickupallows tom measure both the horizontal as well as thevertical schottky-spectrum .The emittance measurement device formerly installedbehind the cyclotron was reinstalled in front of the COSY-ring . It is located at the arm of the former H,-injection. Toprevent the COSY-vacuum from the out gassing of thetargets the target chamber is separated from the COSY-vacuum by means of a thin stainless steel foil serving asstripping foil for the H' simultaneously .Tests with the residual gas beam profile monitor turned outthat the channel plates used in the device are not radiationresistant . To protect the channel plates from the radiation anew vacuum chamber with blinds was designed andinstalled . The blinds cover the channel plates as long asthey are not used for the measurement.The last quadrupole magnets in front of the BIG KARLtarget were supplied with additional windings similar to theones installed at TOF to allow for steering ofthe beam. Thewindings for the horizontal plane together with anadditional dipole in front of the target allow changing theangle of the incident beam instead of moving the BIGKARL.Alignment activities were mainly related to theexperimental installations and the setup of the secondpolarized ion source that still occupied a lot ofmanpower .For COSY11 and ANKE positions of detectors andmagnets were measured. A lot of time was spent for thealignment of the JESSICA target installation . Besides theseactivities we could give some support to other institutesinside FZJ for special measurement problems .After it turned out that the thickness of the aluminumwindows at ANKE couldn't be reduced below 0.5 rum westarted collaboration with an engineering office at Munichto develop a fast shutter system for COSY. This office has

149

developed a shutter that closes an aperture with a diameterof 50 nun within 4 ms . Aim of the new development is toclose the aperture of 150 mm we have at COSY in less than10 ms . This is sufficient to protect the electron cooler evenifa foil at the D 1 of ANKE bursts .Besides these hardware activities we made detailed costestimates together with the department of structuralengineering for the setup of the TETHYS-spectrometer inthe east hall of the cyclotron building . Alternatively welooked at the Costs to replace BIG KARL by TETHYS orto install TETHYS behind the JESSICA experiment .Together with the cost estimates for the beam line to theeast hall we started to look at the civil engineering costs forthe setup of a new injector linac in the lorry gateway of theaccelerator hall.

150

8

6 . ION SOURCES AND BEAMTRANSPORT

The two unpolarized H- ion sources [1] operated reliablyfor a total of 5819 hours in the year 2000, including 217hours of D- operation and some time to study ion opticalelements for the polarized ion source [2] . One source, the"IBA"[1], was modified for operation with deuterium . Thissource enabled us to extract a deuteron beam of ca . 10 PAfrom the cyclotron, which made it possible to accelerate4*1010 deuterons inside COSY. Polarized beams were usedin two blocks of about 3000 hours total beam time for theexperiments EDDA and TOF. For the first time thepolarized H- beam intensity reached 1 EtA after cyclotronextraction. A large number of significant modificationsresulted in an operation with a reliability hithertoinaccessible . At the same time the intensity of the polarizedbeam inside COSY reached values up to 3*109 protons atmaximum energy having a polarisation ofabout 70%.

Pulsed

Thermal ' Cs

Heat/CoolElectrode Ionizer Reservoir unit

Fig 1 : The new cesium ionizer module with the additionalpulsed electrode and the new combined heating and coolingfunctionality.

The key to this fundamental improvement was a completeredesign of the cesium ionizer and a new pulsed mode ofoperation that had been developed to the point of routineoperation over months . The electrically pulsed operation ofthe cesium ionizer was already demonstrated in 1998 [3] .The newly designed advanced cesium ionizer was set inoperation for the first time in spring 2000. An additionalpulsed electrode hardware and a permanent air coolingcircuit were integrated in the new set-up (Fig . 1) .For the pulsed operation the temperature of the cesiumreservoir had to be precisely controlled in the range from50°C to 80°C, depending on the characteristics of thetungsten contact ionizer and the desired intensity. Thecooling system is able to decrease rapidly the reservoirtemperature from 400°C to 40°C in about 6 minutes, anessential prerequisite for efficient operation . The coolingcapacity is such that the Cs-reservoir could be operated at40°C with the thermal ionizer having its full operationaltemperature. The parameter space for the operation of thisnew system was carefully mapped . Fig.2 shows examplesof the variation of the pulse shape and height whenincreasing the pulsed extraction potential . The voltage ofthe pulsed electrode was varied from 4 kV to 8 kV relativeto the beam potential of 45 kV. Up to 12 mA Cs+ wasextracted . For an extracted Cs+ current of 5 mA the lengthand the shape of the Cs+ pulse was closely studied by

Ion Sources at COSY

R. Gebel, B . Dahmen, W. Derissen, R. Enge, H.P . Faber, O . Felden, N. Gad, M. Glende, H. Hadamek, A. Müller,U . Rindfleisch, P . von Rossen, N. Rotert, Th . Sagefka, H . Singer, J. Bisplinghoff', P.D . Eversheim', D. Rosendaal'

153

mcl

Lhl~ , ,.!!,J, -®� , .!1..OIIIV . .H,4,O,Oms' A.' C111 J L60Y,

Fig . 2 : Cs+ pulses from the pulsed ionizer . The pulseheight varies from 5mA to 12 mA with increasedextraction voltage of the pulsed electrode . (Total time is40 ms)

SÖ.Un1Y X4 .00ms A

I � I.60h

Fig .Fig . 3 : Cs+ pulses from the pulsed ionizer. The pulselength varies at a level of 5 mA with increasedtemperature of the Cs reservoir. (Total time is 40

varying the temperature of the cesium reservoir . In theexample shown in fig . 3 the temperature was increasedfrom 50°C to 59°C until the pulse shape reaches the desired20 ms pulse length which is the maximum length useful forinjection into COSY . Operation takes place at about 0,5 Hzto ensure a steady equilibrium for the delicate processestaking place on the tungsten ionizer surface . By this kind ofoperation the serious detrimental effects of the cesiumbeam inside the polarized ion source are reduced byapproximately two orders of magnitude which allowed anoperation of 9 weeks without servicing of the cesiumionizer or other parts of the source .

' Institut für Strahlen und Kernphysik, Universität Bonn

References[1] H . Beuscher et al ., IKP Annual Report (1996)[2] P.D. Eversheim et al., IKP Annual Report (1996)[3] R. Gebel et al ., IKP Annual Report (1998)

[4] R. Gebel et al ., IKP Annual Report (1999)

0Q -10" -20

-30-40

1 .

Qlump pulser extension for operation in decelerationphase

The EDDA experiment measures polarization data as afunction ofbeam momentum during the ramping phase . Toovercome the intrinsic resonances, which usually destroypolarization, fast changes of the vertical working point arenecessary . These changes are possible using the qjumppulsers. The number ofjumps was limited to 10 jumps permachine cycle . Modifications in the driver software nowallow 20 jumps to conserve the polarization also duringdown ramping . Thus this experiment is able to nearly getdouble the beam time .2.

Function generationFunction generation at COSY is based on a sequence ofcubic polynomials. In some cases local modifications haveto be introduced to improve the magnet behaviour. Tools tomake such modifications have been developed earlier.They have been extended to allow trapezoidal modi-fications . Now all these modifications are tracked andlogged into a file from which they might be recalled later,either manually using the fgen-editor or automatically atstart up ofthe user interface for the main magnets .A second block of activities aims at a refinement of theexcitation functions which are used for calculating thecurrent vs . time function for the main magnets . Themeasured magnetic properties of the dipoles have beenreinvestigated. Averaging over the 24 dipoles is found tobe appropriate. The measured integral of the B-field alongthe proton trajectory is required to make a 15 degreebending angle . Thus a function momentum vs dipolecurrent is defined. This function is made available formachine development purposes . Using steps of 10 MeV/cis sufficient to allow a spline interpolation which isglobally only little sensitive to local modifications of theunderlying table. Using this algorithm acceleration up to2.6 GeV/c is possible with strongly suppressed dispersiondriven orbit components and orbit movement . Furtherinvestigations are going on . Figures 1 and 2 show acomparison at about 2.6 GeV/c.

Application Programs and Accelerator Model

N. Bongers, C . Deliege, M. Simon, R. T611e

1H~~;

0 50 100 150 200Position [m]

Fig. 1 : Orbit movement during acceleration between injectionand final energy in steps of 500 ms using the old standardfunction generation.

403020

E 100

ö -10X -20

-30-40

final momentum 2585 McVlc,newfunction generation

0 50 100 150 200Position [m]

Fig. 2: Orbit movement during acceleration between injectionand final energy in steps of 500 ms using the new functiongeneration. Notice the minimized movement. Remainingdistortions are due to absence oforbit correction .

3. Injection orbit and its correction with the backlegwindings

The main (15 degree) bending magnets in COSY haveknown imperfections and measured misalignments which,however, are small enough to be tolerable . Furthermore themagnetic length of dipoles and quadrupoles is individuallyreduced according to the installation environment. On theother hand orbit deviations (mainly in the horizontalplane) are the consequence which limit the effectiveaperture of our synchrotron. The orbit, which is acollection of less than 30 beam position monitor readingsdepending on the number which contribute to themeasurement, can be controlled by using horizontalsteerers . To compensate differences in the magnetic lengthof the dipoles each dipole is equipped with a correction coil(backleg winding ; BLW). Since power supplies are nowconnected to 8 of these coils preparations are made to usethe BLWs for orbit correction as they correct at the originof magnetic errors . In a first step the response of thehorizontal orbit to a fixed excitation of every single BLWwas measured. The response matrix is now created. Usingthe pseudo inverse of that rectangular matrix settings forthe BLWS can be calculated . Measurements are going on.

. . .0 . . 500ms-1000 ms

40 --r--1500 ms

30 -x-2000ms--.-2500ms20

E 10 A

7 . SPECTROMETER BIG KARL

J . Engel, R . Jahn, K . Kruck, H. Machner, R. Maier, U . Rindfleisch, P . v . Rossen, R . Tölle,GEM- and MOMO-Collaboration

A special workshop was held at the IKP in theForschungszentrum Rilich in April that centered aroundthe future physics program to .be performed with the largespectrograph BIG KARL (ref 1). The focus was onphysics of high interest that would at the same timeuniquely exploit the special characteristics of the largehigh resolution magnetic spectrograph . It wasunanimously agreed that in the following fields significantcontributions can be expected :

- Precision measurements

- Symmetries

- Exotic particles and states

- Few body dynamics

- Hypernuclei

Quite a few new ideas and proposals have been outlined ofwhich some have already been successfully presentedbefore the program .advisory committee (PAC) . The recentadvances of the COSY accelerator have added much to thefeasibility of some of the proposed experiments . Thisconcerns the availability of polarized protons withintensities that are up by one order of magnitudecompared to the years before and the successful injectionand acceleration of deuterons with 4.1010 particles insidethe cooler ring .

In the continuing effort to adapt the spectrograph to theactual needs of the experiments a large vacuum chamberthat had been used in the early days ofthe instrument hasbeen reactivated. These alterations stood in directconnection with the exclusive Tl-production on light nucleiperformed by the GEM group using the reaction p +6Li -'713e + rl . Due to the massive changes that have taken placemeanwhile at the spectrograph a number of modificationswere necessary to fit the 4.5 t chamber at its new location .With inner clearances of 98 cm, 198 cm and 198 cm(h,w,l) it provides ample space to accommodate an arrayof different detectors . The important advantage of such aset-up is that one avoids the exit window that ejectilesusually have to pass before they can be recorded indetectors . Equally important is the prevention of multiplescattering and energy loss for the ejectiles under

Magnetic Spectrograph BIG KARL

observation penetrating the air. These concerns are notrelevant in connection with lighter particles at higherenergies. But in this case the aim was to resolve 7Li and7Be at relatively low energies which necessitated theabove modifications . A test run has been completed thatconfirmed a very good particle resolution in the focalplane and gave essential information concerning thesuperimposed background.

The measurements to look at isospin breaking have beencontinued by the GEM collaboration . The experimentalset-up had been refined to the point that even the highbackground originating from the close-by beam dump didnot impair in any serious way the quality of the data .Events were successfully measured at two additional beammomenta for the reactions p + d -' 3H + 7r+ and p + d -'3He + no which were recorded simultaneously to avoidany uncertainties coming from target thickness or beamnormalization.

The MOMO collaboration used its set-up to obtaincomplementing data for the two-kaon production based onthe reaction pd -+ 311e K+ K- . Data for two additionalenergies were taken with settings of BIG KARL thatoffered sufficient overlap to ensure the desired continuityfor the analysis . Preliminary findings support theassumption of only s-wave two-kaon and (D-productioncontrasting sharply with the results of the analysis for thetwo-pion production in the reaction pd -' 3He 7c+ 7c- . Forthe (D-peak cross sections of about 1 nbarn was deducedvarying of course with the center of mass energy abovethreshold . This clearly observable low cross section peakis an indication of the high luminosity and goodbackground suppression which were obtained with thisset-up .

References

[ I ] "Physics with Big Karl" Berichte des ForschungszentrumsRilich, Jill-3804, ISSN 0944-2952

158

8. - RADIATION PROTECTION

In the annual report 1999 the measures necessarybefore the erection of the JESSICA experimentwere described . In 2000 the experiment was builtup and the measures for the radiation protectionwere carried out : the extension of the personalsafety system was installed, tested and taken inoperation.The acceptance test by the expert oftheauthorities was made in April ; no deficiencieswere ascertained. The extension of the radiationsurveillance system was accomplished likewise .Also for this test there were no deficiencies . Thedose rate measurements near the experimental areaneeded for the confirmation of a sufficient shiel-ding could not yet carried out because at this dateno regularbeam operation to JESSICA were possi-ble . But first provisional dose rate measurementsshow that for the existing experimental configura-tion (e.g. continuous beam) a little exceeding oftheallowable dose rate value is to expect.A further experimental equipment relevant to theradiation protection is the superconducting accele-rator cavity . Because of the intensive X-ray pro-duction during operation a side shielding with athickness of 100 cm and a roof shielding with 50cm was built . Besides a personal safety system wasinstalled. The software used is based onthe COSY-PSA. Because of the prototype character of theexperimental installation the intensity ofthe X-rayscould not exactly enough determined beforehand.For that reason a radiation surveillance system forthe continuous measurement of the radiation wasneeded . This system was planned, installed, testedand taken in operation. The license for the opera-tion of the superconducting cavity was given inJune 2000 . The acceptance test by the expert led tono objections .For the controlling ofthe maximum dose exposurein the COSY inner hall during beam operation inthe ring the neutron doses are measured perma-nently at the access doors to the ring and on theroof shielding ofthe ring . For the determination ofthe annual doses the dose values are stored conti-nuously . The figure shows the annual doses in theCOSY inner hall for 2000 . (The positions are : doorunder the staircase into the the inner hall (1), atCOSY 11 (2), at the e-cooler (3), at ANKE (4), atthe beam extraction (5), at injection (6), at COSY

Radiation protection

O. Felden, J. Gbbbels, K. Krafft, H. J . Probst

13 (7), at EDDA (8) and on the roofshielding (9)) .Figure : Annual neutron doses at the positions of

1 2 3 4 5 6 7 8 9Positions of the neutron monitors

the neutron monitors .

In connexion with the compilation and determina-tion of the data for the injector linac radiationprotection caculations and estimations were neces-sary, too . For the given beam parameters (max.particle energy: 70 MeV, mean beam current : 1,2gA) a thickness of 180 cm concrete as side shiel-ding (reducing the dose rate to 2.5 gSv/h) is neededif a possible stay in a distance of 3 m to radiationsource is assumed; for a distance of5 m a thicknessof 160 cm concrete is necessary .The determination ofthe sky shine dose rate showsthat without roofshielding the allowable value in adistance of 100 m is exceeded by a factor of 100 .Therefore the linac room is to be shielded above .As for the COSY ring a roof shielding of 50 cmconcrete is sufficient, because for this thickness themaximum annual dose at the fence of the FZJ is0,75 mSv. The estimations of the neutron acti-vations (ground water, soil, shielding concrete,cooling water) gave as result negligible activityconcentrations . The determination of the air acti-vation amounted to atotal activity concentration of15,5 kBq/m3 assuming the number ofair exchangesas in the COSY ring. The annual activity emissionwill come to ca . 61 GBq.

162

IV. EUROPEAN SPALLATIONNEUTRON SOURCE (ESS)

9 . TARGET PHYSICS

10. ACCELERATOR COMPONENTS

9 . TARGET PHYSICS

NESSI-Collaboration: D.Filges, F.Goldenbaum, R.D. Neef, K.NÜnighoff, N.Paul, H.Schaal, G.Sterzenbach,A. Tietze, M.Wohlmuther(FZ-Jülich) ; A. Letourneau, J. Galin, B. Lott, A. Peghaire(GANIL-Caen) ;M. Enke, C.-M.Herbach, D. Hilscher, U. Jahnke(HMI-Berlin)

The NESSI experiment is motivated by the appli-cation orientated aspect, which aims at the imple-mentation of the target station of the planned spal-lation neutron source ESS [1], as well as by thestudy of fundamental physics of proton-induced spal-lation reactions. Experimentally the topic of produc-ing most efficiently usable neutrons is examined sys-tematically by the NESSI-Collaboration for differentboundary conditions . High-energy transport codesare validated or improved with these data .

wa.Oüw 1.06

C

öb

1.07

1.04

1.03

target length

Figure 1 : Additionally produced neutrons by reac-tions of n, p and ir± within the scintillator liquid for1 .2 GeV p+Pb as function of the target thickness(diameter 15 cm). The lower picture shows the rel-ative contribution of n, p and 7rß. Calculations arebased on HERMES .

In the meantime the Berlin Neutron Ball (BNB) wassimulated exactly and calculations have been exe-cuted enabling the estimation of additionally un-desirably produced neutrons induced by reactionsin the scintillator liquid . This contribution or datacontamination depends upon target thickness andamounts to 2 to 6% (see Fig. 1) . For all target thick-nesses the neutrons penetrating into the scintillatorliquid dominate the pions and protons concerning theproduction of additional unwanted neutrons as thelower panel of Fig. 1 demonstrates . While the rela-tive contribution of the neutrons rises with the targetthickness, the low range of charged particles in thick

targets is responsible for the decrease of contribu-

tions of the protons and pions.

Spallation relevant investigations at COSY

167

Correlation measurements of charged particles andneutrons on thin targets give extensive insight of thecomplex spallation process and the different phaseson the excitation and the subsequent deexcitation ofhot matter . In particular the H- and He- productioncross sections are of great importance for estimationsof damages of target- and structure- materials of theplanned spallation source . Exactly these H- and He-measurements show large discrepancies not only be-tween experiment and theory, but already among dif-ferent models themselves as demonstrated in Fig. 2.

Figure 2: He- production cross sections (measuredand simulated) as a function of various target mate-rials for 0.8 GeV proton induced reactions.

Partly, these discrepancies within the models are un-derstood : On the one hand the energy originallytransferred to the nucleus during the intra nuclearcascade is differently re-distributed in various exit

channels [2] and on the other hand strongly differentCoulomb barriers lead to differing production cross

sections of charged particles [3, 4] .Future experiments at NESSI are dedicated to the

completion of the production cross sections of the n,

p, d, t, He-isotopes and the IMF for light structure

materials (C, Al, Fe, Cu, Nb. ..) and for heavy targetmaterials (W, Pb, Hg . . . ) .Research supported by TMR Program (Con-

tract No . : FMRX-CT98-0244), German Helmholtz-

Strategy Fonds and French program GEDEON .References :

[2]

F.Goldenbaum et al ., Proc. of the Int. Conf. onAdvanced Monte Carlo for Rad. Phy., Lisbon,Portugal, 23-26 October (2000) .

cö

v

The European Spallation Source Study, vol III,rep. ESS-96-53-M, ISBN 090 237 6659, (1996)

C.M.Herbach et al., Proc . of the SARE-5meeting, OECD, Paris, July 2000 .

[4]

M.Enke et al ., Nucl . Phys . A657, 317 (1999) .

1 .02-

I

--0--

.I . . . . I . . . . I . . . .I . . . . I . . . . I . . . . I . .a0 " n

0.9r 0.8 _ p _ä " rz+ +Ti

0.7

ä 0.60.50.40.30 .20 .100 5 10 15 20 25 30 35

C0

Ö

Üö'. ..U

'bLwE

x

- G Schaefer 59A Blerl620 Goebel64

- C2 Green 880 Michel 95

NESSI 98NESSI 99

- (a "cu-1oary)

Figure 1: Left panel: compilation [1] of p+Fe Re-production cross section data as a function of incidentproton energy. The lines have been obtained with theindicated codes; LAHET(RAL) and LAHET(ORNL) re-fer to different evaporation-fission models, which are op-tionally available in LAHET. The NESSI-99 results arepreliminary. Right panel: same for p+Ta .

For p+Fe the helium production cross sections ob-tained in the NESSI-experiment are about a factor of 2smaller than from other recent experiments (Michel 95) .The cross sections as calculated with the LAHET- andHERMES-code are somewhat smaller than the NESSIdata in the case of p+Fe while for p+Ta HERMESand LAHET(RAL) predict larger cross sections andLA-HET(ORNL) smaller ones . The calculations with theINCL code are in good agreement with the data of bothreactions : p+Fe and p+Ta.

Helium production in thin targets

NESSI-Collaboration : C.-M. Herbach, M . Enke, D. Hilscher, U. Jahnke, V. Tishchenko (HMI-Berlin) ; D . Filges,F. Goldenbaum, R.-D. Neef, K . Nünighoff, N. Paul, H. Schaal, G. Sterzenbach (FZ-Jiilich) ; A. Letourneau, J. Galin,B . Lott, A . Pdghaire (GANIL-Caen) ; L. Pienkwoski (Univ. Warshaw) ; W.U . Schr6der, J. Toke (Univ. Rochester)

A compilation of published data [1] for proton inducedhelium production shows a large dispersion as can be

1.4seen in the left panel of Fig. 1 in the case of the spalla-tion reaction p+Fe . That is why the NESSI collabora-tion had started a campaign to measure the productioncross sections of charged particles and neutrons for GeVproton induced spallation reactions in thin targets [1, 2] .Recent NESSI data are also shown in Fig. 1 for p+Fe(left panel) and p+Ta (right panel) . The data for bothreactions are compared with calculations obtained withthe Liege Intra Nuclear Cascade (INC) code coupledwith the GEMINI evaporation code referred to as INCLin the following, theLAHET andthe HERMES code . Inthe case of the LAHET code two options were employedfor the choice ofthe subsequent evaporation-fission mod-els assuming the Coulomb barriers to be independent of(ORNL) or to decrease (RAL) with excitation energy.Further details of these codes and the employed param-eters have been described in [1, 2] .

168

0.8

0.6

0.4

0.2

0

3.5

3

2.5

2

1.5

1

0.5

0 20 40 60 80 20 40 60 80

2.5

2

0.5

05

Ztarget

Figure 2 : Experimental [1, 2] and calculated helium pro-duction cross sections for 0.8, 1.2, 1 .8, and' 2.5 GeVproton induced reactions as a function of target atomicnumber Zt.,yet. The thick solid line refers to INCL,the dashed-dotted or dotted line was obtained with theLAHET-code . Note the different scales of the left andright panels . The NESSI-99 results are preliminary.

The observed agreement between data and calculationswith the INCL code is found also for all other targetsincluding heavier targets as is shown in Fig. 2. In con-trast to this the LAHET code, with the two versionsof evaporation models differing by assuming constant(dashed-dotted line) or with the excitation energy de-creasing (dotted line) Coulomb barriers, under- or over-estimate, respectively, the helium yield considerably .The observation that the calculated helium productionis smaller for LAHET(ORNL) than for INCL/GEMINIdespite very similar Coulomb barriers for He and largermean nuclear excitation in the case of LAHET can beunderstood by the overestimation of LAHET(ORNL) ofproton evaporation (due to smaller barriers for p) andthe neglect of 5He emission [2] .This work was partly supported by the GermanHGF-Strategiefonds project R&D for ESS, the FrenchGEDEON project, and the EU-TMR project ERBFM-RXCT980244.References[1] M. Enke et al ., Nucl . Phys . A 657 (1999) 317, and

references therein.[2] C.M. Herbach et al ., Proceedings SARE-5 meet-

ing, July 2000, OECD, Paris, France .

800 MeV 1200 MeV

. " . " cwl~rmmiuvl.oaru.>

" N6S51-SS

1800 MeV

...

2500 MeV !f

. . .

NESSI-Collaboration: C.-M. Herbach, M. Enke, D. Hilscher, U. Jahnke, V. Tishchenko (HMI-Berlin) ; D.F Goldenbaum, R.-D . Neef, K. Niinighoff, N. Paul, H. Schaal, G. Sterzenbach (FZ-Jiilich) ; A. Letourneau,

B. Lott, A. Peghaire (GANIL-Caen) ; L. Pienkwoski (Univ. Warshaw)

For proton energies between 1 and 4 GeV the neutronproduction per proton in thick targets of heavy materi-als such as Pb is increasing almost linearly with protonenergy [1] . What consequences does this observationhave for the radiation damage induced in the window ofthe target station of spallation neutron sources? In or-der to produce the same number ofneutrons at 4 GeV asat 1 GeV only about 1/4 of the incident proton currentis needed . In the following we will investigate whetherwith the reduction of the proton current the induceddamage due to helium gas and atom displacements de-creases correspondingly and thus could result in an in-crease of window life time .

zc.

' 10

x

Damage induced by GeV protons in window materials of spallation neutron sources

' e Schaeffer 59Merl 62

o Goebe164- O Green 88- 0 Michel 95

e

Fe Ta

-INCL.. . .,. LAHET(RAL)- - LAHET(ORNL)-- " HERMES

10 -1 1 10 1 10Proton Energy (GeV)

Figure 1: Proton induced He-production cross sectionson Fe (left panel) and Ta (right panel) per producedneutron in a Pb spallation target in units of mb/n as afunction of incident proton energy. The employed n/phas been taken from [1] .

For investigating the radiation damage induced by thedeposition of helium gas oflow mobility in a metallic ma-terial the helium production rate per produced neutronin a thick target (downstream of the window) can beconsidered as a good figure-of-merit: QHe/n where aHeis the helium production cross section and n the numberof neutrons produced in thick targets (35 cm long and15 cm diameter Pb cylinders) per incident proton . Thisratio aHe/n is shown in Fig. 1 for the window materialFe (left panel) and as an example for a heavy materialTa (right panel). In the case of Fe we observe a dras-tic decrease of helium production per produced neutron.From 1 to 4 GeV aHe/n decreases from 17 to 6 mb/n.For a heavy material such as Ta the helium productionis about 2 .5 times larger than for Fe and furthermorea decrease with proton energy sets in only above about3 GeV. Thus if helium gas production would be a criti-cal parameter for beam induced radiation damage higherincident proton energies would clearly be more advan-tageous for steel windows.A second important structural damage is due to the pro-duction of atom displacements in window materials

169

b 104

n.o.

wmbx

10 3

10 2

400300200100

p(GeV)+Fe p(GeV)+Ta

1 2 3 4 1 2 3 4EP (GeV)

Filges,J. Galin,

Figure 2: With the code INCL (thick lines) and LA-HET(RAL, ORNL) (thin lines) calculated proton en-ergy dependence of the damage cross sections ad ofhydrogen (H), helium (He), and heavy residues (HR) ;He/dpa ratio. 0-He/0'd for beam exposed Fe (left) and Ta(right) windows with a thickness of 2 mm .

caused by proton induced spallation products, in par-ticular by recoiling heavy residues (HR) . Since the LA-HET code was employed extensively to calculate thecorresponding damage quantified by the displacementcross section Qd the results obtained with INCL havebeen compared [2] with those of LAHET. This com-parison is of particular importance since the two codesdiffer considerably in the prediction of other quantitiessuch as mean excitation energies after the prompt in-tra nuclear cascade, recoil energies of HR, and produc-tion cross sections of light charged particles [3]. Fig. 2shows the result of this comparison. Both codes resultin almost the same and constant damage cross sectionswhile the ratio of He production to the displacement peratom (He/dpa=QHe/Qd) is strongly increasing with pro-ton energy in the case ofthe two versions of the LAHET-code (RAL and ORNL) while it is almost constant forthe INCL-code. The observed approximately constantdamage cross section above about 1 GeV means that theproton induced damage decreases as well with increas-ing incident energy for the same amount of neutronsproduced in a thick target .This work was partly supported by the GermanHGF-Strategiefonds project R&D for ESS, the FrenchGEDEON project, and the EU-TMR project ERBFM-RXCT980244 .

References[1] A. Letourneau et al ., Nucl . Instr. and Meth. B 170

(2000) 299, and references therein.[2] D. Hilscher et al ., J. Nucl . Mater. (2001) in press.[3] C.-M. Herbach et al ., Proceedings SARE-5 meet-

ing, July 2000, OECD, Paris, France .

HRINCL

LAHET(RAL,ORNL)

. .. . ... ;~,°

O

Composite Particle Emission in 2.5 GeV Proton Induced Reactions on An

NESSI-Collaboration : A.Letourneau, J.Galin, B.Lott, A.Pdghaire (GANIL-Caen) ; M.Enke, C.M.Herbach, D.Hilscher,U.Jahnke, V.Tischenko (HMI-Berlin) ; D.Filges, F.Goldenbaum, R.D.Neef, K.NÜnighoff, N.Paul, H.Schaal,G. Sterzenbach (FZ-Jülich) ; L.Pienkowski (Univ . Warshaw); W.U.Schr6der, J.Toke (Univ . Rochester)

The emission of composite particles such as 2' 3 H, 3'4'6 He,Li has long been recognized as an important decay channelin spallation reactions. The pioneering experiments ofPoskanzer et al . [1] have shown that the emission of thesecomposite particles could not be accounted for by a singleevaporation mechanism . Indeed, the emission is far frombeing isotropic in the emitter frame and the energy spectraexhibit a high-energy tail in excess of the usual evapora-tive component . Further experiments [2] have confirmedthese findings at different bombarding energies and forseveral target nuclei . It was also shown that the neighbor-ing isotopes 3He and 4He have very different behaviorswith a strong and weak component of non-evaporativeparticles, respectively . However in all these studies theunderlying reaction mechanisms could not be investigatedthoroughly due to the lack of additional experimental in-formation .

Taking advantage of the very exclusive data brought bythe NESSI detector arrays a detailed study of compositeparticle emission was conducted on the 2.5 GeV p+Aureaction . For this purpose 6 telescopes made of successive80 and 1000 pm thick AE Si diodes backed by 7 cm thickCsI crystals were installed in the BNB scattering chamberand inserted as part of the BsiB at 30°, 75 (twice)°, 105°(twice) and 150° . With these telescopes, perfect isotopicseparation was achieved and energy spectra up to 200MeV were obtained . For the first time the spectra could beinvestigated as a function of excitation energy, E*, inferredon an event-per-event basis from the number of associatedemitted neutrons and light charged particles.

References:

10

10

^ob 10N

110.10

0 50 100

170

By confronting the measured energy spectra with those ofthe simulated evaporated spectra at a given E*, the fol-lowing conclusions could be drawn :- the multiplicity of non-evaporative particles increaseswith E*.

- the relative abundance of non-evaporative particles de-creases with increasing E* .

- among all emitted charged particles, 4He is the least"polluted" (<10%) by the non-evaporative componentwhich makes 4He the best probe of E* and also of thethermalization time t [4] .

10

In the current two-step model of intra-nuclear cascadefollowed by evaporation, the emission of composite parti-cles is made possible during the evaporation stage, only. Inthe intra-nuclear cascade step only nucleons and mesonsare emitted. In the present work an implementation ofcoalescence has been made within the INCL2.0 code de-veloped by J.Cugnon [3] in order to generate compositeparticles prior to equilibrium . When a nucleon -either aproton or a neutron- is about to leave the nucleus an in-spection of all other nucleons is made in phase space inorder to check whether one or more nucleons are able tocoalesce with the leaving nucleon . Energy spectra of com-posite particles are thus generated for 2H, 3H, 3He and 4Hewhich can nicely account for the measured data (see figure1). However this is done at the expense of free protonproduction which becomes slightly underestimated whencoalescence is introduced [4] .

150

200 0

soEnergic (MeV)

100 150 2N

Figure 1 : dots : the energy spectra as measured at 30°; shaded area : the evaporative component; histogram : the sum of theevaporative and coalescence components for 2,3 H and 3,4He . For 'H, the upper and lower histograms represent the simulatedemission (sum ofevaporated (shaded) and INC components) without and with coalescence, respectively .[1] A.M. Poskanzer et al., Phys . Rev. C3 (1971) 882 ; [2] R.E.L.Green et al ., Phys . Rev. C35 (1987) 1341 ;[3] J.Cugnon, Nucl . Phys. A 462 (1987) 751 ; [4] A.Letourneau et al ., to be published .

First Neutrons from JESSICA

The target reflector and moderator test facility for theEuropean Spallation Source ESS called JESSICA is basedat COSY and had produced its first pulsed spallationneutrons in August 2000 .This ESS-like target mock-up is made of a 1:1 scaled95 cm long liquid mercury target surrounded by a 1 .3 mdiameter and 1 .2 m tall reflector vessel filled with leadrods . Inside the reflector there are 4 moderator positionsand beam-line inserts as designed for the ESS; one ofthemis filled with a real moderator for the test purposes, theother three are void . Unlike the NESSI experiment atCOSY where spallation physics at thin and thick targets isinvestigated within a limited but well defined geometry,the experimental program on JESSICA targets on:1 .) the validation and gauging of various Monte Carlo

Codes (namely MCNP-X) to simulate the spallationprocess in short pulsed the target, neutron transportfrom the target and reflector, and eventuallydissipation of the neutron energy at the moderator ofvarious materials . Corner stone experiments will serveas an input key to a subsequent digital optimisationprocedure of the final target design and engineeringstudy.

2 .) Experimental scrutiny of highly efficient advancedcryogenic moderators with coherent solid stateproperties that enable the rapid energy dissipation ofthe pulsed neutron beam due to collective highlypopulated solid state modes like the low energyvibrational modes of solid methane. A fast moderatorwould not only shorten the pulse width butsimultaneously brighten the source for the particularbenefit of high resolution neutron scatteringinstruments : more intensity and better resolution.

However, the utilisation of solid state moderators is notstraight forward as there are undesirable side-effects :Radiolysis in solid methane rapidly produces highlyreactive radicals and thus short life time . Considerableneutron absorption and nuclear activation may prevent theuse of magnetic Lanthanides as a moderator material .Thus, a concerted action of nuclear and solid state physics,nuclear chemistry and process engineering is needed toprovide new and feasible moderator concepts to whichJESSICA can provide the experimental test bed andworkshop. In respect of this important technical andscientific potential a global collaboration of 12 leadingneutron research labs was born to support JESSICA, todefine and fulfil its experimental program .After the bulk installation of the target and reflector vesselthe operation license for JESSICA was granted in April2000 . In parallel the COSY accelerator was furtherdeveloped also to produce a short pulsed proton beamdespite its initial design for a slow extraction . Using theelectron cooler the first 300 ns broad pulsed proton beamfor JESSICA was produced at an energy of 1 .34 GeV (ESSenergy), an intensity of 5 - 10 8 protons per pulse and a reprate of O.lHz. First neutrons were obtained from aprovisional ambient water moderator placed into thebottom upstream position. Fig. 1 shows the time-of-flightspectrum of this first neutron spectrum of JESSICA.

ceN

NC03

1000

Soo

e

A,(t)= ~I(2E,.

2 .1 O eV7c(134 GeV)@ -5 .10'ppp,0 .1 Hz)

first rletrtrons ott JESSICAAugust 2000

ambient water moderator

0

2500

Son

756neutron time-of-filght (ps)

Fig. 1 : n-tof-spectrum : JESSICA H2O moderator

In good agreement with theoretical expectations there aretwo contributions to the neutron tof spectrum, the slowingdown region at neutron energies > 130 meV and theMaxwellian part of the thermalised neutrons . Inaccordance with the ISIS parameters of the ambient watermoderator both parts are combined with a somewhatempirical switch function, hence the time differentialneutron flux from the moderator surface is well describedby eq. 1 :

JE.. exp

1

(D,

T 2(+exp

(

x-'

-w,At

with the kinetic neutron energy En=0.5mn (L/t) 2 . In fact,only the source amplitude parameters (J,(D) were fitted tomatch very well the experimental neutron tof-spectrum(fig . 1) . Noteworthy is the very low background inside theJESSICA cave. Fig . 2 shows the JESSICA hardware ofthis first beam to target experiment in August 2000 .

,_,

Fig. 2: ESSlike targetprototype JESSICA : p-beam (fromtop, reflector vessel and 1-Hg target with neutronfighttube (from centre to left top)

References :[1] R . D . Neef, Proc. ICANS XIV, ANL-98/33 (1998) 441[2] H. Tietze-Jaensch, Physica B 276-278 (2000) 102[3] D . Filges & H. Tietze-Jaensch, ESS 99-98-T, (1999)[4] D . Filges et al., Proc . AccApp, USA (1999)[5] http://www.fzyuelich.de/ess/MT/JESSICA/JESSICA .html

[6] H. Tietze-Jaensch, ESS 99-99-M-4 (Feb 2000)(7] H.Tietze-Jaensch et al., Proc . ICANS XV, Japan 2000

daäEQmamro

The, experimental program of the PISA (Proton In-duced SpAllation) project aims at the measurement of to-tal and double differential cross-sections for products ofspallation reactions on a wide range of target nuclei (C- U), induced by protons of energies between 100 MeVand 2600 MeV These data are needed in order to vali-däte and possibly improve the simulation codes allowingquantitative estimation of structural changes of irradiatedmaterials . Such calculations are of great interest for thedesign of the target station and components of the Eu-ropean Spallation Source ESS. The experiment will beperformed at the internal beam of the COSY accelerator.The project is described in details in ref. [1] .

During the past year further development of the ex-perimental apparatus took place . The reaction chamberand vacuum components forthe detection arms have beendesigned and are under preparation . The installation ofthe chamber at the COSYring is scheduled for March2001 .

PARTICLE IDENTIFICATION WITH THE BRAGG-CURVE DETECTOR0 .4

0.35

0.3

0 .25

0.2

0.15

0 .05

0

_._ . . :_. ... . .. ..L .. ._ ..._._ .. . ..L. ..._. ... .._. .. .i_. .. ..._ ... ..._' . .. .. .... . .. ..

0 0.5 1 1 .5 2 2.5 3 3 .5Total Energy [MeWnudeon]

Fig . 1 : Identification of ions with a proto-type Bragg CurveDetector. For light particles clean resolution even for isotopesis possible JLi and '31,i), as recently measured in a testexperiment in Catania (Italy).

Each of the eight detection arms consists of two Mul-tichannel Plates (MCP) working as "Start"and "Stop" de-tectors for the time of flight measurement, a Bragg CurveDetector (BCD) for particle identification andkinetic en-ergy measurement of intermediate-mass spallation pro-ducts, and a set of double layer scintillation detectors- fast and slow (phoswich) - in order to identify lightcharged evaporation and spallation products like p, d, t,He .

Development of the PISA experimental setupThe PISA collaboration

The design and results of the first test of the BCDwere presented earlier [2] . In the year 2000 new tests ofa proto-type BCD have been performed for a variety ofbeam particles ranging from 6Li to 160 and energies atINFN LNS Catania in Italy. The accelerated ions speci-fied above have been elastically scattered on a gold targetand registered by the BCD. Figure 1 confirms very goodcharge and energy resolution of the BCD. Isotopic iden-tification for light ions is possible - note the very clearlyseparated spots of events for 7Li and 6Li .

The telescope for the time of flight measurement iscomposed of two MCP detectors in Chevron configura-tion. The channel plates are manufactured by GalileoCorporation whereas the suitable housing has been de-signed and built by ourselves (fig . 2) .

":":"

Fig. 2 : Assembly forparticle detection with the multichannelplate detector. For description see text.

The particles to be registered are passing the 20luglcm2 thick carbon foil and knock out some 5-electrons .These electrons are accelerated towards the MCP in theelectric field between foil, accelerating grid and secondchannel plate . The particular voltages are chosen to ob-tain the highest multiplication factor in the channel plates(107) and to warrant the best signal to noise ratio. Itwas checked that the best performance of our MCPS isachieved for voltages of2000 V between first and secondchannel plate and around 400 V between carbon foil andaccelerating grid .

Timing properties of MCPs were measured at theaccelerator of the Heavy Ion Laboratory in Warsaw,Poland where few, low intensity beams of various ionspassed through a telescope of two such assemblies spacedby 27.4 cm . The measured resolution of the time of flightis equal to 1.1 ns . The major contribution to this valuecomes from the energy spread of the beam, which is esti-mated to be 920 ps . The influence of the electronics isnegligible (80 ps) . Taking into account these values one

can state that timing resolution of our telescope is equalto 580 ps .

The results of the test of phoswich detectors are pre-sented in another contribution to this annual report .

References[1] The PISA Collaboration, IKP/COSY Annual Report

Preliminary Test of the Phoswich Detectors for the PISA ExperimentThe PISA collaboration

We plan to measure total and differential cross sec-tions of spallation products for proton-induced spallationreactions on different targets [1] . The energy and chargeof the heavier spallation products (Z >_ 3) will be deter-mined using Bragg curve detectors combined with chan-nel plate time-of-flight detectors [2] . For measuring lightspallation products (Z = 1, 2) we are planning to employphoswich detectors placed behind of the Bragg curve de-tectors . For COSY vacuum safety reasons the exit flangeof the Bragg curve detector should be made of stainlesssteel of 0.5 mm thickness .

Fig . 1 : The "slow" (AE) versus "fast" (E) componentsspectrum from a phoswich detector.

We are using the phoswich scintillation detectors ofconical-hexagonal shape, produced by BICRON Corpo-ration . The face of the detector is a 1 nun thick slow

1999, p.175[2] A. Budzanowski et al, IKP/COSY Annual Report1999, p.176[3] Another PISA Collaboration contribution to this re-port

(940 ns decay time) CaF2(Eu) scintillator - acting as anenergy-loss (DE) detector and a 313 mm thick fast scin-tillator BC-412 (3 .3 ns decay time) - acting as energy (E)detector. Particle identification is possible via AE-E tech-nique for H- and He-isotopes . The front cross section ofthe phoswich detector is a hexagon of 25.2 mm diame-ter. In these phoswich detectors 10-stage HammamatsuHTV 2060 photomultipliertubes are used. Due to energylosses of particles in the "thin" slow scintillator the en-ergy range of correctly detected light particles is 15-150MeV/nucleon .

In a preliminary test experiment the registrationof the light particles was performed using the 1 .4 GeV/cproton beam. The phoswich detector was placed at thedistance of 70 cm and at the angle of 60 degrees with re-spect to thick carbon target . The anode signals from thephotomultiplier were split into two branches, fast and -slow. Separate discriminators produced "slow" (long)and "fast" (shorter) gate signals . The analog signals weredigitized in separate charge-to-digital converters LeCroy4300B using "fast''and "slow" gate signals . The durationof "fast' 'gate is 150 ns and the "slow" one 800 ns .

The DE-E spectrum is shown in Fig . 1 . Thelines of p,d, t isotopes and alphas as well as the punch-ing through particles are visible .

We plan also to use phoswich detectors with de-graders forregistration ofhigherenergy light particles butwith poorer energy resolution.

References[1] The PISA Collaboration, IKP/COSY Annual Report1999, p.175[2] A. Budzanowski et al, IKP/COSY Annual Report1999, p.176

174

10. ACCELERATOR COMPONENTS

Abstract

System Optimisation of a Superconducting Linac for the European SpallationSource ESS

A superconducting high-current proton linac for the ESShas been discussed as an option for a Next GenerationNeutron Source for Europe ESS [1] . Considerably costreduction for operation and - possibly - investments mightbe achieved due to experience at presently ongoingprojects . In this paper a cost-optimised technical layout of asuperconducting linac for the high energy end of theproposed accelerator is presented .The superconducting elliptic cavities are assumed to

accelerate H- from 70 MeV to 1334 MeV (0.4<ß<0.9) . TheRF accelerating structures are designed for 700 MHz. Aparametric cost optimisation is done in terms of (i) thenumber of cells per cavity, (ii) the number of cavities percryogenic module, (iii) the focusing elements, (iv) the RFSystem, and (v) the more conventional facilities .Our results favour a superconducting system in terms of

operating and investment cost. A significant reduction ofinvestment could be achieved by raising the electric peakfield in the cavities from 25 MV/m up to 40 MV/m-

1. Description of the reference systemThe basic parameters of the proposed layout are listed in

table 1 . The SC linac will accelerate the beam from70 MeV up to 1334 MeV at an average current of 3.75 mAcorresponding to 5 MW beam power at a repetition of50 Hz. A pulse length of 1 .2 ms is required for filling the 2accumulator rings . The time macro structure results in aduty factor of 6 %. The time micro structure inside thepulse is 360 ns beam-on and 240 ns beam-off time . Theaccumulator uses the beam-off time for maintaining abeam-free section in the circulating beam .The 700 MHz RF system is powered by 1 MW klystrons .

The 6-cell cavities are operated in the 7c-mode . One cryomodule accommodates 2-4 cavities . Six groups (families)of cavities are proposed for the acceleration . Their designparameters are given in table 2 . where and ß,,, indicatethe particle velocity range .

S. Martin, W. Bräutigam, M. Glende, R. Maier, G. SchugForschungszentrum Jülich, Germany,

C.-A . Wiedner, MPI für Kernphysik Heidelberg

The low-ß groups 1-3 may be critical for elliptic cavities .More R&D and prototyping needs to be done for energies< 200 MeV. Alternatively spoke-type cavities - beyond thescope of this investigation - are discussed elsewhere [2] .The arrangement of cavities and their design energy

follows from a required efficiency of > 95 % at the RFpower [3] . Other cavity parameters are given in table 3 e.g .lengths of the individual cavity and the cavity group, thenumber of cavities per group and the number of klystronsper group. Each cavity requires one RF window assuming aload of 600 kW per power coupler.

In table 4 the energy and power characteristics areshown . The maximum power per cavity varies from120 kW in group 1 to 581 kW in the last group . The energygain per cavity varies between 2.2 and 10.7 MeV.

Table 1 : Basic parameters of the superconducting ESSlinacMaximum beam power 5 MWMaximum energy 1334 MeVMaximum ß (v/c) 0.91Injection energy 70 MeVInjection v/c 0.4Average current 3.75 mAPeak current (pulse average) 63 mARepetition rate 50 HzPulse length 1 .2 msDu factor 6

Frequency ' 700 MHzCavity structure type ellipticMode of operation R modeNo. of cells per cavity 6Max. load per coupler 600 kWMax. klystron power 1 MWAccelerating phase angle -25 deTransverse focusing structure doubletNo . ofquadrupoles 98Phase advance per period <90 degQuad insertion warm) length 1 .2 in

The overall energy gain (real estate energy gradient) is aslow as 1 .1 MeV/m while on the high energy end 4 MeV/mis possible . Due to less efficient use of the acceleration fieldcaused by the mismatch between the particle velocity anddesign velocity the average efficiency is Tsyneh,= 0.97 [4] .The peak power Ppe~ k= 79.7 MW corresponds to an averagepower consumption of 5.32 MW for the conversion into abeam power of4.8 MW.

2. The cost evaluation modelThe costs are evaluated in a top-down way for the most

important components of the accelerator system . The cost178

parameters are analysed using commercial software[5] . Thedependence ofthe capital investment on (i) the acceleratingfield Eaee, (ii) the final beam energy, and (iii) the total beampower are shown in table 6 .For the reference design the total capital investment

amounts to 193 M¬ . It consists of (i) acceleratorcomponents (86 M¬), (ii) mains (63 M¬ ), (iii) buildings(26 M¬ ),

(iv) infrastructure

(13 M¬ ),

and (v)

coolingsystems (5 M¬) .

2.1 Cost modelfor the accelerator componentsFrom table 5 it is evident that the cryogenic components

prevail in costs . The cavities have been designed fordifferent ß-values with the codes MAFIA, OPERA andSÜPERFISH [6] . These specifications are input for aprogrammed mechanical design [7] of the cryo modulesemploying the AUTOCAD code.

rfable 5 : Details ofcost for theSC components

Cavity

37.1 M£Coupler

20.7 M£HOM coupler

3.8

M£Tuner

2.8 M£Support .

3 .8 M£Cryogenics

10.3 M£Vacuum

0.66 M£Diagnostic

2.3 M£

accelerator componentsWarm components

Quadrupoles 2.7 M£Bellows

0.29 M£Beam pipe

0.04

M£Diagnostic 0.47 M£Vacuum 0.94 M£Surveying 0.18 M£

The cavity costs are estimated using cost coefficients of425 16/kg for Nb material . The assumed volume of the rawNb material contains a contingency factor of 3 compared tothe volume of the machined cavity . The cost for one celldepends on the design velocity - based on the RF design :Costee�=29.8+6.5*ßDeS;en+3.3* p2Design (with Cost,,,, in kE) .The required manpower for the mechanical, chemical,electrochemical treatment, and the final quality control isestimated to be 5 man days per cell which enters as a costterm of 1 .435 k£ per cell and amounts to 9 k£ per 6-cellcavity .

For the power couplers a price of 110 k£ has beenassumed, for the Higher Order Mode couplers 20 k£ perHOM.

In addition we have assumed the following expenditures :Cost per tuner (one for each cavity) - 15 k£, mechanicalsupport for the cryo module - 80k£ .The total costs for one cryo tanks are 165 k£, 192 k£,

221 k£ for 2, 3, 4 cavities per tank, respectively .For the compensation of cryogenic losses by electric

power the following conversion ratios are used :P,,/Peryo = 840 at 2 K, P,,/P.Y.= 250 at 4 K, andPoi/Po,yo = 14 at 80 K .

Table 2 : Optimised cavity design values Pd... and therange of operation given by ßn,in and ß,nax . The equivalentener ies are also indicated.

group kin Nes. ßinax Enmin EDes . EmaxNo. /MeV /MeV /MeV

1 0.37 0.38 0.41 70 74 932 0.41 0.44 0.49 93 106 1373 0.49 0 .51 0.58 137 155 2034 0.57 0.60 0.67 203 237 3305 0.67 0.71 0.79 330 389 5816 0.79 0.82 0.91 581 714 1345

4-6 0.57 0.91 203 13451-6 0.37 0.91 70 . 1345

group cavity No. of length No . ofNo. length cavities group klystrons

/m /m1 0.48 12 20.2 32 0.56 16 28.2 83 0.66 16 29.7 84 0.77 24 47.4 245 0.91 36 75.9 366 1 .06 84 190 84

4-6 144 313 1441-6 188 391 163

Table 4 : Maximum power consumption P themaximum (AEn , ,) and average energy gain (AE,,,.) per6-cell cavity . Tsynehc is relevant [4] for the averageefficienc

DEgroup Pm, x AE,a,x DE,, real P'~ P.,./

cav . cav. cav . estate Ts,,,h,. Group Group/kW /MeV /MeV MeV/m /MW /MW

1 120 2.2 1.9 1 .1 0.98 1 .4 0.092 177 3.3 2.8 1 .6 0.97 2.8 0.183 263 4.9 4.1 2.2 0.98 4.1 0.284 340 6.3 5 .3 2.7 0.97 8.0 0.535 445 8.2 7.0 3 .3 0.98 15.7 1 .056 581 10.7 9.1 4.0 0.98 47.7 3.19

4-6 581 10.7 7.9 3.7 0.98 71 .4 4.771-6 581 10.7 6.8 3 .3 0.98 79.7 5.32

2.2 Cost Modelfor the Power Sources, MainsThe main power consumption is that of the klystrons

followed by the compensation of the cryogenic losses, andthe installation of the power transport, conversion, andcooling systems . The breakdown ofthe mains costs for thereference case in table 6, co1.2 (62 .6 M£) is given intable 7 .The most influential cost factors are the klystrons . Here

we assumed costs ranging from 210 - 360k£[9] for thepower range of 200 kW until 5 MW.

Table 7 : Cost breakdown for klystrons and electric

3. ConclusionsA design system has been developed which allows the

cost optimisation of superconducting accelerators .This model was developed to analyse the dependence of

the costs on the accelerator parameters .The largest impact on the total costs is given either by

the peak field in the SC cavities (see tab.6 : col.2 vs . col . 3),or by the maximum power allowable in one coupler(600 kW is above the state ofthe art) . More R&D needs tobe done in both directions .

Doubling the energy at half the current in order to keepthe power constant (see tab .6 : col.2 vs . col. 6) is only 10%more expensive at acceleration of protons . This could be amotivation to study the acceleration of HZ+, which has noelectromagnetic ionisation losses during acceleration but isstill useful for charge exchange injection into theaccumulator rings .The higher energy is more attractive because the

acceleration from 1300 to 2700 MeV is accomplished withß =1 cavities, which are well studied and allow a peak fieldof Epek 40 MV/m.

REFERENCES[1] J. Kjems, A.D . Taylor, J.L. Finney, H. Lengeler,

U. Steigenberger (ed .), "ESS - A Next Generation NeutronSource for Europe", Vol III, "The ESS Technical Study",Copyright : ESS Council, March 1997

[2] E . Zaplatin, "A Spoke RF Cavity Simulation withMAFIA", RF-SC'99, Santa Fe, Nov . 1999

[3] W.F . Bräutigam, S.A . Martin, G. Schug, .E.N . Zaplatin, P.F . Meads, Y.V. Senichev, "DesignConsiderations for a Superconducting Linac as an Optionfor the ESS", PAC1999

[4] T.P . Wangler, "Principles ofRF LinearAccelerators", Wiley series in Beam Physics andAccelerator Technology, 1998

[5] The authors are indepted to UGS, TDL atD 09350 Lichtenstein, Germany, for making available theUGS software for the evaluation of expenditures

[6] E . Zaplatin et al., "SC RF Cavity Development forESS", contribution to this conference

[7] Work done on contract for the FZ-Juelich by UGSand CADCON, H. Seli6

[8] The prototypes costs are taken as a fraction of 5 °/"of the total capital investment which is more uncertain formodules ofhigher gradient. This will be updated in the nextstage .

[9] SNS, Private communication . Recent costevaluations let expect significant higher klystron costs.

Table 6 : Dependence of total capital investment onelectric peak field (col. 3), beam power (col. 4) bydoubling the energy, and increase of the maximumenergy and the accelerating field (co1.5) . The referencedesign is shown in column 2 . The E, nax=40 MV/mrequires 2 couplers per cavity in rou no. Sand 6 .ParametersE.. 1334 1334 2668 2668 MeVCurrent 3.7 3.7 3.7 1 .9 mABeam Power 5 5 10 5 MWEpees 25 40 25 40 MV/mLength 391 278 655 444 mAccelerator 86.0 70.4 139 .5 95 .7 M£Mains,RF 62.6 48.8 104.4 70.4 M£Building 26.1 18 .5 43 .7 29.6 M£Infrastr . 13.3 12.5 14.9 13.6 M£Coolin 4.9 4.9 9.2 6.2 M£Capital invest 193 ' 155 312 216 M£Man powerPlanning 51 41 83 57 myPrototyping [8] 64 51 103 71 myConstruction 1285 1034 2078 1437 myOperation 96 77 155 107 m /CostPlanning 3.9 3.1 6.2 4.3 M£Prototyping [8] 9.6 7.8 15.6 10.8 M£Construction 82.3 66.2 133.0 92.0 M£Operation 23 22 43 29 M£/Optimised manpowermy. total 1401 1127 2266 1566 mym. . cost 96 77 155 107 M£

installationCost klystrons[9] 45.1 MECost circulators 11.3 M£Cost RF piping 1.4 M£Cost installedpoower accelerator 4.9 M£

General aspects

System Design for a Superconducting Version of the ESS Linac

W.F . Bräutigam, M. Glende, S.A. Martin, G . Schug

A few system layouts have been optimised during the lastyear . The high-energy part (above 70 MeV) of the ESSlinac has been discussed using superconducting ellipticaccelerating structures. The system design starts from a firstorder beam transport, the electric and mechanicalparameters of the acceleration cavities . The optimisation isdone in terms of the accelerating gradient, the number ofcells per cavity, the beam transport system, the RF sourcesand components, and the parametric cost figures .

Figure 1 : Schematic view ofa single 5-cell cavity(ß=0.5,ß=0.9) in a cryogenic tank

Modules for the description of the systemThe basic RF module consists of the superconducting Nostructure resting in a cryogenic tank . An example for such a5-cell cavity is given in Figure 1 . The length in thedirection of the beam is a critical parameter for the cost ofthe total system. In figurel is demonstrated that the detailsofthe cryogenic tank needs further development in order toreduce the longitudinal extension of the module. The detailsof RF sources are not given in the sketch . For the layout ofthe

high-energy part of the linac we discussed the usage of 5-and 6- cell cavities. The overall parameters are shown intable 1 . The criterion for the determination of the numberof mechanical identical cavities is given by thesynchronous part of the transit time factor Ts . This factormeasures the efficiency for the usage of a cavity applied toparticles of a velocity ßp not matching the geometric celllength ß0X/2 . This Ts is calculated in a ray tracing program.

1.0101 .0000.9900.980

~' 0.9700.9600.9500 .940

0.950

Synchronous part of transit time

0.975 1.000 1 .025

PiPo�ia

1.050 1 .075 1.100

The ray Figure 2 : Synchronous part of the transit timefactor . T9 is calculated by ray tracing through a set off96 6-

cell cavities moving the beam from ß=0.791 (595 MeV) toß=0.911 (1340 MeV). The design value is ODesign=0.825 .

tracing results fit with the analytic formula of Wangler [3]within 0.1 %.

As a typical number of cells per cavity we choose N=6 . Thetransit-time factor for such a 6-cell cavity is shown in thefigure 1 .

,Q groupingThe cell number N=6 have been chosen for ESS because

of the smaller influence of the end cells compared toN=4,5 . We have slightly rearranged the high energy linacpart by fixing the maximal surface electric field to 25MV/m. The ratio Ep,*/E., has been calculated in [4] .The number of groups of identical cavities to be builtshould be as small as possible for an economicmanufacturing . On the other hand, a criterion has been usedto tolerate a maximum decrease of the transit-time factor of5% at the ends of the groups of identical cavities . Hence, 6different groups of identical cavities will be necessary toaccelerate the beam in the linac from 70 MeV up to 1334MeV. The geometric velocities for the 6 groups areßDesign0.38, 0.42, 0.49, 0.58, 0.68 and 0.79 . In a next stepthe energy gain throughout the whole . group has beenoptimised by varying the centre velocity factor ßDcsign . Theresult ofthis optimisation is shown in figure 4 .

1 .3801 .360

m 1 .3401 .3201 .300

~ 1 .280~, 1 .260m 1 .240LU 1 .220

1 .200640.000

Energy gain in the cells

~JWIWA,

rw11NOMA W_'mr®~z4®®rsWAK.

660 .000 680 .000 700.000 720.000Energy/MeV

740.000

Figure 3 : Energy gain per cell ßDesign =0.825 (725 MeV).The maximum phase 0 ofthe center cell is set to -20 0 .

Power consumption In the cavitiesEpeak=25MV/m phase=-25degree

Figure 4 : The power consumption per cavity for the 6different groups .

The energy gain for each group of cavities is optimized,keeping the average longitudinal phase advance per cavityconstant and varying ßDesign value during the optimization .The transverse optics follows either FODO or doubletfocusing .

A summary of the optimization for the whole system isgiven in table 1 . The cavities for ßnaign values below 0.5 aretopic of Rirther R&D. It is certainly state of the Art to usesuperconducting cavities for the acceleration from 210MeV up to the maximum Energy 1340 MeV using thegroups No . 4 to 6 .

References[1] J.Kjems, A.D.Taylor, J.L.Finney, H.Lengeler,

U.Steigenberger (ed.), "ESS - A Next GenerationNeutron Source for Europe", Vol III, "The ESSTechnical Study", Copyright: ESS Council, March1997

[2] B.Aminov, A.Gamp, E.Haebel, H.Heinrichs, H.Piel,J.Pouryamout, Th.Schilcher, D.L.Schrage, G.Schulz,S.Simrock, C.H.Rhode, and R.R6th, "Conceptualdesign ofthe Superconducting High Energy Linear H"-Accelerator for the Future European Spallation Source(ESS)", ESS 96-60-L, December 1996

[3] T.P. Wangler, "Principles of RF Linear Accelerators",Wiley series in beam physics and acceleratortechnology, 1998

[4] E. Zaplatin,

"Design Study for

SC Proton LinacAccelerating Cavities", ESS 104-00-A, Mlich,July 2000

Table 1 : Grouping of the ESS-SC cavities (6 Cell)

Group 1 2 3 4 ,54-6

6total1-6total

beta min 0.37 0 .42 0.49 0 .58 0 .68 0.79 O.S8 0.37beta design 0.38 0 .45 0.52 0 .61 0 .71 0.82beta max 0.42 0.49 0.58 0 .68 0 .79 0.91 11.91 0 .91E Min 70 96 136 21.0 345 595 210 70MeVdesign 78 110 157 246 398 722 MeVMax 96 136 210 345 595134213421342MeV

cavity length 0.49 0 .57 0 .66 0 .78 0 .92 1 .06 m. of cavities 12 12 20 28 40 96 164 208

length system 18 .5 19 .5 34.3 51 .3 78 .6 202 332 404mGrad . r . estate 1 .41 2 .02 2 .17 2.64 3.18 3 .69 3.40 3.14MeV/mCav./klystron 4 3 2 2 1 1

. kl strons 3 4 10 14 40 96 150 167Energy gain per cavity

E max 2.47 3 .70 4.26 5.54 7.1.0 8 .80 8.80 8.82MeV2.18 3 .28 3 .72 4.84 6.25 7 .77 6. .90 6.11 MeV

average .979 .977 .972 .974 .980 .980 .979 .978Power cons . per cavity

max 139 209 239 310 399 497 497 497kWPmin 132 195 221 288 376 469 188 132kW

av ./gr . 0.1 0 .2 0.3 0.6 1 .0 3 .1 4.7 5.3MWtot. 1 .6 2 .5 4.7 8.5 15.6 46 .6 70.7 79AMW

Dewar

ESS Test Cavity : First RF Measurements

W. Bräutigam, O. Felden, M. Glende, R. Maier, H. Meier, A . Schnase, G. Schug, H. Singer, R. Stassen

Cavity installationThe 5-cell 500MHz test cavity [1] was delivered by ACCELand installed to the radiation shielded area [2] in April of thisyear . The cavity was filled with liquid helium and we startedthe first measurements. A low-speed VXI system is used tosurvive all temperatures inside the cavity and to control thevacuum pressures . The data (26 channels) are taken every1 .5 minutes and are stored into files to get the history of thetemperature and pressure behaviour of the cavity .

The cryogenic systemThe test cavity has been embedded into a nearly closedhelium circuit (Fig. 1) .Liquid helium is delivered in dewars of 500 to 1000 litres,which are placed outside the radiation shielding. The LHe isfilled into the helium tank of the cavity through a transferline(length -- 9m) . The flue gas is warmed up to roomtemperature and send via a gasline to our refrigerator . Here itis cooled down to 4 K and again stored in dewars .

Helium Tankwith Resonator

Fig. 1 : schematic view of the cryogenic setup

The capacity of the Helium tank is about 310 litre. Filling ittakes about 4h depending on the pressure inside the dewar .The standby losses are about 4.7 W. To estimate the loss ofhelium during standby times, we took the LHe-transferlineoff and measured the amount of flue helium gas with acalibrated gas meter for about 24h . During filling times thelosses raise up to 50 W because of cooling down the RF-resonator, the helium tank and the transferline.

RF setupThe measurement system consists of a frequency regulatingcircuit using a RF-Generator that has an analogue frequency-tuning input port (Fig. 2) . Its output power is delivered to themixer input and a portion of the forward signal drives thecavity . Two field probes are installed in the cavity. One isused to generate the frequency-regulating signal at the FMinput of the generator and the other one is calibrated todetect directly the accelerating field . We use two oppositelyacting attenuators to regulate the RF power . An increase ofthe power to the cavity is compensated by attenuating thepower from the cavity to the mixer input. The mixer outputsignal characterizes the frequency behaviour ofthe cavity

182

and is used to detect e.g . the influence of mechanicalresonances and microphonics effects .The attenuators of the transmission lines were calibrated asgood as possible to measure the QöEacc curve accurately .

Fig. 2 : RF-measurement setup

1,0E+10

1 .0E+0s

low passfilter

Q-Ear,. measurementsThe acceptance tests of the cavity were done as the first RFmeasurements. The frequency-regulating circuit is necessaryto measure Q0 values in the order of 1E9. We took the Qo-

Eacc curve (Fig. 3) at nearly critical coupling in order tomeasure Q0 as accurate as possible . This data well agree tothat measured at CERN in a vertical cryostate at a limited RFpower of 200Watt . We achieve in our lab higher acceleratingfields up to nearly 8MV/m using a 500Watt amplifierwithout detecting a quench. But the measured Qodegradation at increasing RF fieldstrengths and themonitored x-ray levels point to active field emitters insidethe cavity . At the higher fields we saw moving light spots onthe glass vacuum window which seem to be produced by thestrong electron loading . Even the mirror installed outside thecavity to allow a indirect view with a camera was tarnishedby a brown film . The estimated dose of the mirror is about30Gy during one minute .

1,0E+08

Fig. 3 : Q,,-E.,, curve

phaseshifler

forward power

,~ reflected power

vxlSystem

Frequency-tuningsystemsTwo tuning systems are installed at the cavity : The roughtuning system simultaneously squeezes the five cells using astepper motor driving a chain gear . The fine tuning systemuses three piezo-elements operating in parallel mode. Thesepiezos , have often been used for many differentmeasurements. The system consists of three high-voltagesources, each driving one piezo element. The control voltageof the sources is adjustable from 0-10 V and is amplified bya factor of 100. The corresponding frequency shift of theresonance is demonstrated in Fig. 4 (here up to 5 V) . Thesystem response is nearly flat and shows only littlehysteresis .

1200N1000

t 600

600400

Piezo

200

00 1 2 3 4 5 6

control voltage / V

Fig. 4 : Piezo tuning elements

First high-power testsThe 50OW amplifier in Fig. 2 can be replaced by aSIEMENS 30kW transmitter borrowed from ACCEL. Wechecked that transmitter and completed the high powersystem with a circulator and a high power switch whichallows tests of the SIEMENS transmitter and thesimultaneous use of the former 500Watt amplifier for cavitytests [3].The input coupler of the cavity is adjustable from nearlycritical coupling to a loaded Q of the order of 1E6 . We canreach a filling time of about 2ms at this coupling. Fig. 5shows filling the cavity by 28kW and maintaining the flattopby switching back to 7kW to simulate the beam andswitching off after Ims.

Fig . 5 : First high power test with beam simulation

183

We reached a field-level of about 5MV/m as guaranteed byACCEL applying a forward power of about 30kW and haveoperated with a repetition rate of 50Hz (Fig . 6) . We canoperate without frequency regulating circuit only if themicrophonic noise is minimized by switching off thecryopump and if the system is predetuned .

Fig . 6: Test cavity operating at ESS pulse rate (50Hz)

We started to condition the coupler and the cavity with thispulse scheme. We could see the first results after severalhours of operating with the frequency regulating circuit . Thex-ray radiation detected outside the shielded area wasreduced . Most of field emitters inside the cavity have beendisactivated .By a hazard of the timing-system, the full power of about40kW was delivered to the cavity over several seconds. TheQo of the cavity was reduced by a factor of two and thecavity quenched at nearly 5MV/m. Different methods likewarming up the cavity and cooling down again whilepumping all the time will be done to reach the former datawithout additional chemical treatments .

References[1] H.Vogel et al, A Superconducting Accelerating Test

Module for the European Spallation Neutron Source,PACK New York

[2] Gb.Schug et al, Radiation Protection for ESS Prototype-Cavity Experiments, IKP Ann. Rep . 1998, Ail-3640

[3] A.Schnase et al, Pulsed power amplifier for ESS test ofa 500 MHz superconducting cavity, this annual report

AbstractWe performed measurements and calculations at a coppermodel at 460 MHz. The crossed-spokes acceleratingstructure is under examination as a candidate for ESS protonenergies of around 120 MeV. We show that optimizationsboth with respect to field flatness and to maximum energygain lead to almost identical positions of the tuning system .The energy gain stays at minimum 99 % within the tuningrange of f 2,5 MHz. This is sufficient to overcome eigen-frequency shifts caused by temperature, pressure, andhumidity fluctuations .We work out a procedure to design coupling loops atinternal Q values of several thousands ; the beam power canherein be included. It requires a measurement of Q, MAFIAcalculations and an experimental fine tuning ofthe loop .

Crossed-spokes model cavityThis accelerating structure is being discussed to be usefulfor medium ESS energies [1] . The main components of themodel cavity [2] are

the cylindrical cavity wall (brass), fö 0,32 m * 1 m,4 crossed spokes having central beam holes of 60 mmdiameter,

"

2 end plates as adjustable shorts, here synchronouslytuned,2 small coupling loops at the circumferential wall .40

Aspects of Tuning and Feeding a 5-Gap Spoke Resonator

The 71 accelerating mode at 461 MHz is the first resonanceof a series of 5 circular-H-11 like modes . The dimensionscorrespond to a proton velocity ofv/c = 0,46 (120 MeV).Field measurements and mode identification had also beentreated in [2] .

Tuning behaviour of the cavityRoughly adjusting the longitudinal E.,-field profile leads to aposition tend - 82 mm of the end plates . The MAFIA [6]results and the bead-pull field measurements do notsignificantly differ [3] .The EZ profiles of 4 positions of the end plates arejuxtaposed in Fig . 1 . We have taken the effectiveaccelerating tension Uacc = UoT to be the characteristicfunctional for comparison of the EZ profiles; hereby thestored energy WS was kept constant. This procedure almostprecisely equates the calculation of Eacc = EeT at a fixedvalue of the energy density. The quadratic terms of energyintegral and the lower fields at the beam axis cause thatfixing the energy density is nearly adequate to fixing thepeak electric field strength . So we have got a criterion tocompare the acceleration efficiencies of different electricfield distributions (Fig.2) .Fig . 2 demonstrates that UT decreases only by 1 % shiftingthe resonant frequency by t 2,5 MHz. The optimizedposition of the adjustable shorts is marked : zend,max = 82,38nun . A second approach to find the optimal position starts atthe ratios of the EZ field strengths in the centres of theaccelerating gaps (Fig.3) . Here, we form the RMS average of

Gb. Schug, Ch. Deutsch, R. Stassen, E. Zaplatin

184

the distances to unity of the both different Egap ratios andminimize that characteristic functional. This leads to themarked value of zend,min = 82,33 mm. So, both criteria lead toalmost identical positions of the tuning system. Theprocedure of gap field ratios can conveniently be used foroptimizing the model cavity . Fig . 3 also shows that theabove tuning by f 2,5 MHz shifts the EZ in the end gaps byaround ±20 %.

os

Fig . 1 :

EZfield profiles at different positions tend

of theend plates .

4&'07 s,a7

Fig . 2 :

Acceleration tension Uaoa = UaT at fixed storedenergy vs . shorting-plate position tend

. . ..---NOexmm

Fig . 3 :

Both different EEap ratios vs . shorting-plate positionZend

Influence ofclimate data on the model cavityThe fluctuations of the resonant frequency have beenapproached to get an idea of the measurement uncertaintiesand the necessary tuning range (Tab.1). The values havebeen estimated using data of [4], [5] . Even the fabricationerrors of f 1 mm only lead to a UoT decrease of0,5 %.

Tab . 1 :

Shifts ofeigen frequency by fabrication and climatefluctuations

RF coupling loo of the model cavityThe loop coupling to 50 Ohm forms a transformer togetherwith the cavity . We work out the

0

First step : transforming ratioA transformation ratio ü is defined by

ü = sgrt (R/50 Ohm), where R denotes the ohmiccavity resistance. We calculate it using U(,, W,computed by MAFIA and Q = 5800 taken frommeasurements . Uo denotes the EZ integral withrespect to the a mode, Ws the corresponding storedenergy . We get at the model cavity ü = 272 .Second step : ratio of areas

We set ii = U./UE = A,,/AE correspondingto the induction law (Fig.4) . A(, is set to half thecavity's longitudinal cross-section. We get as firstguess AE = 5,1 cm2 .Third step : ratio of induced RF tensions

Here, UE is taken as a MAFIA contourintegral . Some numerical trials of rectangular loopsare made to set UE = U,,/ii and lead to an loop areaofAE = 4 cmZ.Fourth step : correction by measurements

A L-shaped piece of copper is contacted to

a inner spoke (Fig.4 and Fig .5) . Its reflection

coefficient is experimentally minimized . This

results in an area of AE = 4,7 cmZ.

0

0

0

185

The above 4-step procedure can also determine the loopcoupling to a beam-loaded cavity . The beam power gained inthe cavity correspond to a resistance shunted to R.

.i000000

* o.

ii 0-- - Q p aa . . .~ti~ peu . .

Fig . 4 :

[4]

[5]

[6]

.A :9

Longitudinal cross-section of cavity and couplingloop ; definition of induced RF tensions andequivalent areas

Fig . 5 :

Detail of rectangular loop of Fig. 4 connected to thespoke ("Speiche")

References[1] E. Zaplatin, W. Bräutigam, S.Martin, Design study for

SC LinAc cavities, Proc . 1999 PAC, N.Y., 1999, p.959 . . .61 similarly in IKP Ann. Rep . 1998, Jill-3640, FZJülich, Feb . 1999, p . 195Ch. Deutsch, B. Dahmen, D . Gehsing, A. Richert, M.Schaaf, Gb . Schug, H. Singer, K . Sobotta, R . Stassen, E .Zaplatin, Field-Profile Measurements at a 5-GapCrossed-Spokes Model Cavity, IKP Ann . Rep. 1999,Ril-3744, FZ Jülich, Feb . 2000, p. 181Ch. Deutsch, Messung und Berechnung elektro-magnetischer Eigenschaften einer Beschleuniger-stntktur, Diplom-Arbeit, Jülich-Bonn, Juli 2000F . Kohlrausch, Praktische Physik, Teubner-Verlag,

StuttgartD.R. Lide (Ed .), CRC Hbk. of Chem. a. Phys ., CRC

Press, 1995CST-Gesellschaft für Computer-SimulationstechnikmbH, MAFIA 4 Tutorial (Getting started, a guided tour

through the most common features of MAFIA), May

1997 . See also references [4], [5] of [1] . .

Cause of shift shift

mechanical cavity tolerance 1 mm 500 kHz

Temperature of cavity wall 20 K 200 kHz

air temperature in cavity 20 K 5 kHz

air pressure in cavity 30 hPa 5 kHz

humidity in cavity (30 °C) 50 % 40 kHz

IntroductionHigher repetition rates like 50 Hz for the ESS design [1] or60 Hz at SNS [2] and 75 Hz at CERN Neutrino Factory [3]will require a close look to the mechanical resonances of thecavities . Mechanical resonances can influence the phasebehaviour of the cavity during a pulse which can hardly becompensated by a good control system, even if a lot ofadditional power is available .Additionally, microphonic effects are very dangerous andhave to be examined .

Mechanical resonancesWe used the piezo elements designed for the fine frequencyadjustment in order to detect the mechanical resonances . Astatic electrical tension of 500V at the piezos leads to atuning by 1 .2 kHz . The first measurements were done with asinusoidal excitation of the piezo elements . The piezo systemis fast and limited in our system by the used power supplies .We stimulated the piezo up to 200 Hz . Higher frequenciesare possible but there is no experience about limits by thestresses of the piezos operating at these frequencies andlimits by power dissipation. We measured the mixer outputsignal in the closed regulating loop [4] as response to thestimulation . Fig.l shows the small signal to a stimulus faraway from a resonance .

Mechanical Resonances and Microphonics in a 5cell 500MHz 5C Cavity

Fig. 1 : sinusoidal excitation, no resonance

W. Brautigam, R . Maier, G. Schug, H. Singer, R. Stassen

Fig . 2 shows the dramatic response to the stimulation at amechanical resonance of 119Hz .This strong resonance can also be stimulated if we excite at1/2 or 1/3 of this frequency . This fact - subharmonicexcitation of mechanical resonances - can be a greatproblem for future SC proton accelerators . The scanning ofall resonances in the frequency domain would be too time-consuming. Therefore we applied a step function in the timedomain and calculated the resonances by a Fast FourierTransformation (FFT, Fig . 3) . We have detected mechanicalresonances even applying a low step function at the piezos(50V) .These measurements have been done with all three piezos inparallel mode . So mostly longitudinal resonances were

excited . Even the detection system - the mixer output signal- is very sensitive to longitudinal changes . Additionalmeasurements are needed in order to separate longitudinaland transversal modes. One solution will be the excitation byanother separated system mounted mechanically to e.g. thesupport of the cavity. Therefore, the three piezos can be usedas a detection system . Because of the different mountingpositions, it will be possible to decide whether we excite atransversal or a longitudinal mode .

6,00090100080,000 '0,0006

010005

0,0004

0,0003

0,0002

0,00,01

Fig. 2 : Excitation of mechanical resonances

d: 41.9ms«D: 3 .5ms

C1 Freq119 .0473 Hz

C2 Freq118 .7643 Hz

29 May 200017 :16:22

Besides the mechanical resonances we found the 50Hz andl00Hz line of the ripple of the AC power line.

Fig . 3 : FFT of the response to a 50V step function at thepiezos

Comparison of measured and calculated resonancesDifferent calculation of the mechanical resonances havebeen made . The first calculation made by ACCEL showedthe first resonance far above 50Hz [5] . Additionalcalculation including more details of the cavity in the modelseems to be much closer to the measured data [6] . A preciseannouncement can only be made after additionalmeasurement including the possibility to decide the mode ofthe resonance. The next measurements will be done usingthe piezo elements as a diagnostic tool to measure directly

the shaking of the cavity in the pm range. The firstmeasurements have proved the perturbation of the cavity.We have seen a mechanical resonance during filling thecavity with jiquid helium at about 1-2Hz. This frequency canalso be seen in the frequency regulating-circuit and is stillnot understood .

MicrophonicsThe cavity RF resonance is sensitive to vibrations of sub-punamplitudes because of the high Q. These microphonicseffects causes low-frequency noise in the accelerating fields.Therefore, careful damping of cavity support and otherancillary units are necessary to suppress all mechanicalcavity resonances . High microphonics noise is produced bythe 'Gifford McMahon' cryogenerator (Fig. 4.). Thecryogenerator is connected to the cavity test cryostat toreduce the helium losses [4] . We can see. a phase oscillationcorresponding to the frequency of the pump (about 1Hz) .Even the effects of a turbo-pump can be seen, whichdemonstrates the sensitivity of the system. The microphonicscan't be reduced by feed forward because there is nocorrelation to the pulse repetition rate. But vibration pick-upswill be installed to built an active damping system in thefuture.

Tek Run: Looks/s"! Res

»W it%0UG crf--- ""

requency .! l

' normal:co.tfii"lddlh . . . fit , 2 :dd'

M (.bbs ch3J"'1 .WoVCh3 0.9.V Cf14 509mV

)9.omv.

1.99:1

. . i . . . . : . . . .1 . . . .

11[daj'l I:r12Math t

MUM

MAWCh1+Ch2I rfr(ChI) I in IKChf) Ref3

CII9 9i29 PhanqCH2 3?.1 109 KAU

111d

o- and turbo-pumpo: 19 .dmv4s : -9.2mv

C4 Rfse

=1amplitude

prepared field : -2.2 MV/m

7.F.1 ./ Fir.-I" 10 'IF1 d8/ RCP 0 dB

out cryo-pump

control signal undereditions

Ret4

Fig . 4 : Microphonics effects by different pumps

A quantitative measurement of the microphonics effects wasdone after changing the coupling factor in order to increasethe bandwidth of the cavity ; the loaded Q value was set toaround 1E6 and we were able to measure the amplitude andphase response of the cavity directly using a networkanalyser. The network analyser operated in CW mode at thecavity resonant frequency with a time span of 3 sec .

10'.009l-S .BSBS dB

99tnS

990. .52 118a

. . . . . .... ..

l. . . .... . . .j . . . . . . . . . " i . . . . .. . . . . . . . . . . . . . . .i . ..... ....i..... .. . ..i. . . . . . . . . . .. ... . . . . .i... . .CF.

i. . . ... .

. . . . . . : . . . . t. . . .

....

..... . . . . ......... . . . . . . . . . ... .

...... .

'. . . . .... . .

s

i

. .

. . . . . .WON

. . . . . . . . . .i ..

. . .,. . . . . . ... . .. ..... ... ; . . .... ... . ; . . . . . . . . . . ; . . . . . . . . . .i . . ....: . . .

i. . . . . . . i . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. ... . .i

. . . . . . . . . .i . . . . . . . . . .i . . . . . .. . ..i . .. . . .. . ..i . . . . . . . . . .i . . . . . ... ..i.. . . . . . . . .i . . ... . . . . .i . . . . . . .. . .i . . . . . . ... .

111d Ilr mw .1 1 Nz

PclugP

0 domPEWTER ~9S.99Bu Mflz

Mpg a isrPAN 0 iS

c.z

Fig . 5 : Amplitude and phase response at cryopumpSwitched on/off

187

The frequency regulating loop was opened. The phase shiftsand the amplitude changes were directly measured duringthe time span of about 3sec . The internal RF oscillator of thenetwork analyser was used as reference. The upper twocurves in Fig. 5 show the phase response of the cavity withand without operating of the cryopump. The microphonicscaused by the pump lead to a strong phase-shaking of morethan ±20°. These phase perturbations are not tolerable inaccelerator operation and must be compensated or regulatedby a fast control system .The amplitude response, shown at the two lower curves inFig .5, is completely flat if the cryopump is stopped . Evenwith the relative low external Q-value we can see aamplitude change during the 3 sec if the cryopump isworking.

References[1] ESS A next Generation Neutron Source for Europe,

Volume III,[2] J.R . Alonso, The Spallation Neutron Source Projekt,

PAC99, New York[3] H . Haseroth, CERN Ideas and Plans for a Neutrino

Factory, NuFact'00 Workshop, Monterey[4] W.Bräutigam et al, ESS Test Cavity : First RF

Measurements, This annual report[5] W. Diete et al, A Superconducting Accelerating Test

Module for the European Spallation Neutron Source,PAC99, New York

[6] J.F. Stelzer, Analysis of the dynamic behaviour of theESS superconducting accelerator moduls, to bepublished as ESS Report

Nature of Lorentz-force detunineThe high electromagnetic fields in a superconductive cavityproduce high forces at the cavity walls. The deformations ofthe walls lead to a shift of the resonance frequency calledLorentz-force detuning (LFD). The static frequency shiftdepends on the square of the field strengths and on thestiffness of the cavity . The LFD can be in the order of theresonance bandwidth, especially for elliptical cavitiesdesigned for lower beta values . The mass inertia causes thefrequency shift to be time dependent.The LFD in a pulse mode operation can be described by afirst-order differential equation with the constant K anddynamical time constant rLFD .

Dependence ofHe pressureWe tried to measure the static constant K by measuring thefrequency shift in CW mode with a counter. But the firstmeasurement was mainly influenced by the increase of thehelium pressure caused by the dissipated RF and electron-load power in the niobium walls.

Fig. 1 : Frequency shift by He pressure

The decrease of the resonance frequency amounts to around0.6 kHz (Fig . 1) . This perturbation was reduced by pulsingthe RF power at repetition rates below 1Hz . So, the Hepressure increase was negligible .

Measurement of the LFDWe used the same set-up as for the Q0 measurement [1] . Thepulse lengths were in the order of 1 sec because of the nearlycritical coupling . This coupling strength is necessary to reachthe desired field levels of about 5 MV/m with the 500Wattamplifier.The frequency change has been measured using the mixer-output signal of the regulation scheme also depicted in [1] .Fig. 2 shows the validity of the quadratic law and a LFDconstant of about K=4 Hz/(MV/m)z.Even at the relatively low field design value of our testcavity (5MV/m) the frequency shift of about 100Hz is notnegligible .Besides the constant K, the time delay tiLFD is very importantfor a pulse mode operation. Longer iLFD would allow aneasier compensation of the LFD.

Active Compensation of Lorentz-Force Detuning

W. Bräutigam, R. Maier, G. Schug, H. Singer, R. Stassen

T

cm

wö.c _N

LFD: Determing of the constant K

0 5 10 15 20 25 30 35

Eacä / (MV/m)2

Fig. 2 : Lorentz-force detuning

We have got an estimation of the time constant of the LFDafter commissioning the 30kW SIEMENS transmitter [2] .The higher power enables shorter filling times by changingthe coupling. The system was not predetuned and thefrequency was not regulated with a phase look system. Wetook measurements at three accelerating field levels to showthe development of increasing phase change of LFD (Fig. 3).

M ixcr output signal

Iso -fu

r"1,2 5onrriV:C113 20.0m ON rdli200-11

Fig. 3 : Estimation of the time constant

At low field levels (1) far below 1 MV/m the phase shift isnot significant. Higher field level >IMV/m (2) can also bereached without change of the amplitude during the pulse,but with a time dependant phase . At the highest field level(about 4MV/m) the detuning of the cavity caused by theLFD is so strong that the field decreased . The continuouschange of the mixer output signal during the pulsedemonstrates the high time constant of our cavity . Additionalaccurate measurements have to be done; we estimate a timeconstant of about 5 ms.This high time constant allows a pulse length of lins likeESS without regulating circuit. Before the LFD takes place

-20

-40- ho-ho-_11'qU-601

-80 ,II

too

120

the pulse is descending . For beam acceleration, the phasechange could be corrected at lower power levels .Fig. 4 shows the unregulated operation combining this shortpulse (Ims),and one long pulse (3ms) at 4MV/m. The LFDleads to a so large phase shift at the long pulse that theflattop is descending even if the cavity is predetuned .

Fig. 4: Additional long pulse every third pulse

Active Compensation of Lorenz force detuninf;Stiffening the cavities can reduce Lorentz force detuning butthis method will increase the force that is necessary to tunethe cavity . One way to solve this problem can be the rightchoice ofthe location of the stiffening rings [3] .Another way is to detune the cavity and control the phasechange only with a fast control system . In this case a lot ofadditional klystron power is needed. We tried to compensatethe Lorentz force detuning with a feedforward signal becauseit is a predictable problem . We used the piezo elements ofthe fine-tuning system because they act fast enough and canprecisely be adjusted . The first try to compensate the Lorentzforce detuning is shown in Fig . 5 . We used a simplefeedforward signal . It consists of a fast up-ramp, a littleflattop and a fast down-ramp . The signal ends before wereached the flat top region of the pulse. Without feedfowardwe could see the change of the mixer output signal (R2) andthe amplitude of the field (RI) . The phase change during theflat top is so strong that the field amplitude decreases.

Ref2 10 .0n1' 2,501ns

~1 .' ^7 ri'1211%tip". I .kA t.'

rate : 5Hz!

eId -probe (E �,

5

Vim)

13 Sep 200015:37 :31

Fig. 5 : First compensation of Lorentz force detuning

Now the compensation works at a repetition rate of 5Hz . Weincreased the rep:rate and saw that at a certain rep . ratetogether with the feedforward signal a mechanical resonanceat higher frequency was excited . We have reached a betterdecoupling of the neighboured pulses using a piezo signalbeing one sine wave. This even allows a pulse rate of 50Hz(Fig . 6) as demanded in the ESS proposal .

Tek Run: 100kS /s t

1Sample

10

R7

piezos elements

rV 410111V

al

VIM)

Ch3 10.0MVG4b °*

z0omV

13 Sep 2000

Ref2 1O.Om 2.50ms

17:23:56

Fig. 6: Compensation of Lorentz force detuning with

OutlookThe piezos used for the fine frequency tuning is fast enoughto allow a compensation of the Lorentz force detuning with afeedforward signal . Additional measurements of the cavityresponse will be done to simulate the whole behaviour of thecavity and to construct an analogue or digital [4] feedbackcircuit to compensate all possible errors .We will try to built up a special digital feedback/feedforwardregulating circuit to use low-beta superconductive cavities ina linac .

References[1] W. Bräutigam et al, ESS Test Cavity: First RF

Measurements, this annual report[2] A . Schnase, Pulsed power amplifier for ESS test of a

500 MHz superconducting cavity, this annual reportC. Pagani, RFS Activities at INFN Milano-LASA, 70'workshop of superconductivity, Saclay

[4] S . Simrock, Design of the digital RF control system for

the TESLA TEST FACILITY, EAPC96, Barcelona

. . . . . . . . . ."Power" Piizo

ieflected . . ., . . . .,! . . . .'feedforward

41d-probe (C,,, }LL

SL, r

cnnmb um " . ms ux mb

For the accelerating facilities with big beam final power likethe linear accelerator for European Spallation Source (ESS)/1/ the only option of an accelerating structures for the lowenergy region could be the superconducting (SC) RFcavities . The use of SC structures also is the simplest way ofthe future facility upgrade . At the moment there is a scope ofdifferent already proved SC structures .

For ESS Linac the required energy range which should becovered by SC structures is ß = v/c = 0.2-0.5 . One of themost proper RF cavities for this energy range is a spokecavity (Fig . 1) .

Fig . l SpokeRF Cavity Geometry

The spoke cavity by definition is a coaxial half-wave lengthcavity with an outer conductor turned on ninety degrees sothat its axes is directed along the beam path. An equivalentcapacitance of such cavity is defined by the distance betweenconductors in the center of the cavity along this ax . Adistribution of an electromagnetic field in such cavity is thesame like in coaxial cavity with not homogeneous waveimpedance . The range of application of this cavity is from100 to 800 MHz of fundamental frequency and ß=0.1-0.6 .The limitations of application are defined mainly by theresonance capacitance grow for low values which in itsturn reduces cavity diameter.

From the side of superconductivity the limitations are thesame like in well-known elliptical cavities - to reach as highas possible the ratios between electric and magnetic peakfields on the surface in relation to the accelerating field onthe beam axes (Bpk/Eacc and Epk/E,,c,;) . At the moment theaccepted working values for peak fields Bpk=60 mT andEpk=40 MV/m which results in Bpk/Epk=1 .5 mT/MV/m . Thelast ratio can be used as a measure for the cavityoptimization : if it is above than 1.5 the limitation on Eacecomes from the magnetic field, ifbelow - from electric .

Low-ß Superconducting RF Accelerating Structures

The principles of spoke cavity geometry optimization arediscussed elsewhere/2/. Here we would like to considerproblems of low beta SC structures design for rather high

W. Bräutigam, E . Zaplatin

resonance frequency 700 MHz. First of all, to use this typeof cavity means the use of several hundreds of separate two-gap cavities . As these cavities are superconducting, one hasto think about cryostat either separately for each cavity(which seems rather costly) or to combine several cavities inone cryomodule . In all cases it is necessary to installfocusing magnets between cavities . That looks ratherproblematic for the case of several cavities in onecryomodule . Another problem for few hundred separatecavities use is a rather complicate control system, whichshould support all these cavities. These are the reasons whywe suggest using multi-gap structure similar to the spoke-cavity . Such structure could represent the same cylindricalouter conductor as the cavity tank loaded with severalelectrodes (or spokes) . But as soon as one adds at leastanother spoke in such structure it turns from the coaxialspoke cavity into H-type cavity, which is defined by theelectromagnetic field distribution . This type of cavity alsohas been considered in /2/ . Here we describe some further itsdevelopments.

Fig.2 . Ten-Gap H-cavity ofModified Geometry .

First of all, it is the cavity geometry optimization to reducethe ratio of Bpkfacc. To increase the space available for RFmagnetic field we propose to make cavity tank square rathercylindrical . Another modification related to the spokegeometry . We suggest to make it plane not only in the centerbut also in the outer parts (Fig.2) . This brings not only againmore space for h-field but mainly makes the distribution ofthe current on the spoke more homogeneous.

The results of numerical simulation of such type structureare summarized in Table 1/3/ . From these results the lastoption of geometry with squeezed spokes and square cavitytank is preferable . Conducting these simulations we kept thesame geometry in the center of electrodes . This regiondefines the ratio Epk/Eacc , which is defined from the relativespoke and tank dimensions .

To create an even distribution of an electric field along thebeam path we use additional volumes in the end parts ofthecavity . This adds more space for magnetic field in this regionand modifies e-field profile (Fig.3) .

Table 1. Some Parameters to Compare SC H-Cavities

. :ea -t .aouc.m n .oar=.no t .aoac-at ._n:

Fig .3 . Electric Field Profile along Beam Path in Ten-Gap H-Cavity.

For the cavity frequency tune the back walls of the structurecan be used . The conjunction of these walls to the endelectrodes is made round to give flexibility for theirmechanic deformation. The possible frequency change isabout 10 MHz/mm.

Fig.4. SCH.Cavity Geomeby (700 MHz, ß= 0.2)

On Fig.4 we present the dimension of such structure for theresonance frequency 700 MHz and ß=0.2 .The conducted dynamic mechanical analyses/4/ confirmedthat this type of the structure is much more rigid, whichshould simplify much the problems related to the Lorenzforce detuning and microphonic effects .

A rather complex RF field distribution leaves a hope for alow chance of resonance multipactor discharge/5/.

References[1] W. Bräutigam et al, "Design considerations for the linacsystem ofthe ESS", NIM, B 161-163 (2000) 1148-1153 .[2] E . Zaplatin, "Design of SC RF Accelerating Structuresfor High Power Proton Linac", ESS 104-00-A, Rilich, July2000.[3] Yu . Senichev, E . Zaplatin, "Superconducting MediumEnergy ESS Linac", ESS 00-107-L, Rilich, December 2000.[4] F . Stelzer, "Analysis ofthe Dynamic Behaviour ofthe

Spoke Cavity in the ESS Superconducting AcceleratorModule", FZJ Internal Report, Rilich, 2000 .[5] G. Romanov et al ., "Study of Electron Multipacting un

Spoke Cavity", INR Internal Report, Troitck, Moscow,2000.

- . - MHz 700 700 7000 .2 0 .4 0 .55

i . cm 7 .85 7 .15 7 .15 9 .80 8 .70 9 .10 9 .20. . cm 1 .5 1 .5 1 .5 1 .5 1 .5 1 .5 1 .5

cm 4 .283 4 .283 4 .283 8 .565 8 .565 8 .565 11 .78allthickness

mm 3 .0/ 1 .0

3 .0/ 1 .0

3 .0/ 1 .0

3 .0/ 1 .0

3 .0/ 1 .0

3 .0/ 1 .0

3 .0/ 1 .0

ttf 0 .779 0 .779 0 .778 0 .779 0 .779 0 .778 0 .783

IEk/Eacc 4 .90 4 .93 5 .10 3 .49 2 .63 3 .88 3 .79

JB kIEacc mT/MV/m 9 .20 8 .17 7 .06 10 .07 8 .77 8 .03 9 .76'B k/Ek mT/MV/m 1 .88 1 .66 1 .38 2 .88 2 .41 2 .07 2 .58

11 round square cross round Square cross cross

Abstract

HIGH CURRENT BEAM DYNAMICS IN AN ESS SC LINAC

M. Pabst, K. Bongardt, Forschungszentrum Jülich GmbH, GermanyA. Letchford, RAL, Didcot, U.K.

Three alternative designs of the European SpallationSource (ESS) high energy linac are described . The mostpromising ones are either anormalconducting (nc) coupledcavity linac (CCL) up to final energy or a change at 407MeV to only one group of 6 cell superconducting (sc) el-liptical cavities .

Fully 3d Monte Carlo simulations are presented for bothoptions, optimized for reduced halo formation at the linacend. For the error free matched case, especially the haloformation in the longitudinal plane is more pronouncedfor the hybrid solution with its superconducting cavities,caused by the unavoidable phase slippage, but still quitewell acceptable for loss free ring injection. Simulationshowever for a 30% mismatched dense core, surroundedin addition by 1.5% halo particles are showing few parti-cles with very large amplitudes even in , real space . Thiscase represents halo formation in front to end simulations,caused by current fluctuations, filamented RFQ output dis-tribution and enhanced by accumulated field errors.

1 OPTIONS FOR THE HIGHENERGYPART OF THE 6% D.C. ESS LINAC

The current reference design of the ESS contains a 1 .334GeVH- linac with a5% dutycycle, a50 Hz repetition rateand apeak currentof 114 mA. The beam currentis choppedwith a 70% duty cycle [1] . The radio frequency is 280MHzfor the two front end RFQs and DTLs. After funneling at20 MeV final acceleration to 1.334 GeV is accomplishedin a nc CCDTL and CCL operating at 560 MHz. A sc ver-sion of the high energy linac is also being studied. The 1msec long linac pulse is injected into 2 compressor rings,to produce a final beam pulse length of 1 psec.Any design of the ESS high energy linac must ensure

loss free ring injection. This demands an unfilamented 6dphase space distribution for the linac beam.

Table 1, lists 3 high energy, 6% duty cycle, linac designoptions for a 107 mA, 60% chopped beian using 700 MHzstructures . These were the linac parameters from the ESSstudy [2] . The 700 MHz linac frequency is also the same asconsidered for the CONCERT [3] multi-user facility. Thefollowing conclusions are valid for both 560 and 700 MHzfrequencies, but they are limited to linacs with about 6%duty cycle .

For all three options, a doublet focusing system withwarm quadrupoles is assumed either after 2 nc cavities [2]or after ( 2, 3, 4 ) 6-cell elliptical sc cavities . The acceler-ating gradient is kept constant at EoT = 2.8 MV/m for thenc cavities resp . Eo = (5 MV/m, 8.50 MV/m,13.7 MV/m

Table 1 : Options for the high energy pärt of the ESS 6%d.c ., 64 mA pulse current, 700 MHz linac

for the 3 sc cavities. Two power coupler/ cavity are as-sumed for the ß = 0.8 sc cavities . The synchronous phaseis kept constant at -25° in the nc cells, whereas only the sccavity midphase can be kept constant at -25° as a conse-quence ofphase slippage. All sc cavities are assumed to bemade out of 6 identical cells . The relative ,Q dependence ofthe transit time factor is the same as for the SNS 805 MHzsc high ,0 = 0.76 6-cell cavities [4], obtained from super-fish calculations where end field effects are included . Theaverage transit time factor is smaller by at least 10% thanthe 7r/4 = 0.79 value of ß = 1 sc elliptical cavites . Theaverage synchronous phase per cavity is smaller than -37°at beginning resp . end ofeach sc section .

It is obvious from table 1, that a pure nc ESS linac ver-sion from 105 MeV on is the cheapest in capital cost, butnot in operating cost . A sc ESS linac from 120 MeV onrequires much less peak RF power, but it is in capital costquite expensive and substantial R & D is necessary for the50 Hz pulsed mode behaviour ofP = 0.52 ellipticalsc cav-ities [5, 6], including the ESS 2.7 msec long pulse option

Normal Super- Hybrid solu-conducting conducting tion(nc) linac (sc) linac

Energy 105 - 120-1334 105-407range 1334 MeV: MeV: CCL

MeV: ß =0.52, >407 MeV:CCL 0.65, 0.8 0 = 0.8, sc

Total 631 m 493 m 148 m (nc)length + 267 m (sc) =

415 m# of cavi- 232 212 62 (nc)ties + 116 (sc) =

178# of 116 212 31 (nc)klystrons + 116 (sc) =

147Peak RF 2MW 0.4 MW, 2 MW (nc),power per 0.75 MW 0.75 MW (sc)klystronTotal peak 232 MW 101 MW 137 MWRF Power# of circu- NONE 212 116latorsCryogenic NONE 4MW 3MWpower

[2]. The hybrid solution with its two couplers/cavity is theshortest and the cheapest one for capital plus 20 years op-erating time cost. By having only one coupler/cavity theESS hybrid linac will be longer than the corresponding ncone. Detailed pulsed power tests with 2 couplerstcavity areforeseen for the 500 M13z, /3 = 0.75 sc cavity teststandat FZ Jülich [7]. The open questions are halo formation atthe end of the ESS hybrid linac, resulting from the phaseslippage and enhanced by mismatch.

2 MULTIPARTICLE RESULTS FOR THEERROR FREE MATCHED ESS LINAC

In Fig.

1, 2 results from Monte Carlo simulations areshown for the ESS nc linac at 105 MeV injection and atthe 1334 MeV final energy. All simulations are done with10000 fully in 3d interacting particles. The 700 MIiz bunchcurrent is 107 mA, the normalizedrms emittances are 0.31rmm mrad resp . 0 .47r°MeV . The ratio between the full andzero current tune is greater than ( 0 .6, 0 .5 ) transverselyresp. longitudinally. The ratio between the transverse andlongitudinal temperature in the rest system is 0.66 at injec-tion and about 1 .3 at the linac end . All zero current tunesare below 90° . The rms radii are about 3 mm at injectionresp . 2 mm at the final energy.The results in Fig. 1, 2 are obtained for the error free

matched case. The upper row corresponds to an 6d wa-terbag input distribution limiting each particle coordinatetoV18- of its rms value. As the ESS high intensitync linac isdesigned to avoid all kind of instabilities, driven either byhigh space charge, temperature anisoptropy or resonancecrossing [8], almost no halo formation is visible at the linacend : there are no particles outside 20er�� at the linac end .The rms emittances are changing by less than 10% .

Figure 1 : Input distributionfor the ESS linac with matchedinput. Upper row without, lowerrowwith 1 .5% initial halo

In the lower row 1.5% halo particles are placed ini-tially outside the dense core at the surface of a dd phasespace boundary with 16ervna " Each particle coordinate isnow limited to 4 times its rms value and there are in each2d phase space projection less than 10-2 particles outside

-;'o o . ,. (mm)

S

s

Figure 2 : Output distribution for the nc linac for matchedinput. Upper row without, lower row with 1 .5% initial halo

IN,, About 1% halo particles above 10c,.�,, are foundin simulations of the 2.5 MeV ESS RFQ [9] . Phase spacecorrelations between halo particles ofa bunched beam in aperiodic focusing channel are reported before [8, 10] . Atthe ESS nc linac end there are now about 10-3 particlesoutside 20e,ms, going up in phase space to about 40er,But still all particles are limited to ±10 mm at the linacend which is less than half ofthe assumed 22 mm apertureradius. There are less than 10-3 particles outside ±1 MeV

In Fig. 3 the output distributions are shown for the er-ror free matched ESS hybrid linac. Again the upper row isassuming an initial 6d waterbag distribution without halo,whereas the lower row assumes a distribution with 1 .5%halo . For a constant transverse full current tune of45° inthe sc cavity section the ratio between the full and zerocurrent tune is greater than ( 0.6 , 0.67 ) transversely resp .longitudinally. The ratio between the transverse and longi-tudinal temperature in the rest system is 0.36 at 407 MeVand about 1 .1 at the linac end . All zero current tunes arebelow 90° . The rms radii are about 2 mm at 407 MeV resp.1 mm at the final energy.

Figure 3: Output distribution for the hybrid linac . Upperrow without, lower row with 1 .5% initial halo

By comparing the nc output distribution in Fig. 2 withthe hybrid one in Fig. 3 much more halo formation espe-cially in the longitudinal plane is visible at the end of theESS linac. Less than 10-3 particles are outside ±2 MeVThe inputdistributionwith initially 1 .5% halo particles willlead to single particle amplitudes up to 9 mm at the ESShybrid linac end, well outside the 6 mm boundary value oftwice thebeam core size, predicted by particle-core models[111 . The reason is the phase slippage especially 'at begin-ning and end ofthe sc section, where the beamvelocity dif-fers by ±15% from the cavity design velocity. In the MonteCarlo simulations all particles are experience the change ofthe synchronous phase from cell to cell in the 6-cell cavity.As a consequence, even the rms beam radii are oscillatingalong the ESS hybrid linac, as the nc to sc 6d phase spacematching is done for the average cavity synchronous phase .

3 MONTE CARLO SIMULATIONS OFTHE MISMATCHED ESS LINAC

In Fig. 4 phase space distributions are shown at the final1334 MeV energy forthe ESS nc resp. hybrid linac, assum-ing a mismatched input distribution with 1.5% initial haloparticles . The upper row is showing the nc and the lowerrow the hybrid linac output distributions. Excited is a purehigh mode with 30 % radial and 20% axial mismatch ofthe 3 bunch radii. The high mode oscillation frequency ofabout 160°/period [8] causes halo formation in all 3 phasespace planes as single particle have initial frequencies ofhalf the high mode oscillation frequency.

Figure 4: Output distribution for the nc linac (upper row)and the hybrid linac (lower row) . The mismatched inputdistributionis surrounded by 1.5% initial halo .

By assuming the same 30% pure high mode excitation,butfor an initial distribution withouthalo particles, the notshown resulting phase space distributions for both, the ncand the hybrid version of the ESS high intensity linac lookquite similiar to the shown distribution in Fig . 4 . The onlydifference are somewhat less particles nearby the bunchcore. But all requirements for loss free ring injection arefullfilled : the final normalized transverse rms emittance is

smaller than 0.4Tr mm mrad and there are about 10-3 par-ticles outside 20e,�, Longitudinally there are less than10-3 particles outside ±2 MeV , which is acceptable forenergy spread reduction by the bunch rotation system.

Adding initially 1.5% halo particles to the 30% mis-matched dense core, the linac output distributions in Fig .4 show a few particles withe quite large amplitudes evenin real space. Studies are going on for the motion of theseparticles in the linac to compressor ring transfer line , stilleffected by space charge forces [2] . Unconstrained handson maintenance requires less than 1 W/m uncollected de-posited beam power at linac end and at ring injection.Thisvalue corresponds toless than I '0-7/m uncollected particleloss for the ESS accelerator facility with its 5 MW averagebeam power .

In a periodic focusing system correlated field errors of±1% even for same limited periodes can cause noticablemismatch later on [12] . In front to end simulations ofthe complete ESS linear accelerator, including the chop-ping and funnel lines, the halo formation at the linac end iscaused by current fluctuations, filamented RFQ output dis-tribution and enhanced by accumulated field errors. The soresulting haloformation can be estimated by assuming 30%mismatch of an unfilamented beam, surrounded by 1 .5%halo particles, at the entrance of the error free high energylinac section .

4 REFERENCES[1] I. S . K . Gardner et al ., 'Revised Design for the ESS Linas',

ESS rep ., ESS 99-94-A, Aug 1999[2] 'The European Spallation Source ESS Study', Vol 1-3,

March 1997;1. S . K . Gardner et al, Proc . PAC 97, Vancou-ver, Canada, p . 988

[3] J. M . Lagnielfor the CONCERT Project team, Proc . EPAC2000, Vienna, Austria, p. 945

[4] YCho, 'Prefmanary Design Report: SCRFLinas for SNS',SNS report SNS-SRF-99-101, Dec 99

[5] D . L. Schrage, 'Structural Analysis ofSuperconductingAc-celerator Cavities', Los Alamos report LA-UR-## 99-5826,Jan2000

[6] N. Akaoka et al, 'Superconducting Cavity Development forhigh Intensity Proton Linacs in JAERI', 9 th Workshop onRF Superconductivity, Santa Fe, USA, Nov 99 ; E. Chishiroet al ., 12 th Symposium on Accelerator Science in Japan,Wako 99, p . 236

[7] E.Zapladn et al., 'SuperconductingRFCavity Developmentfor ESS', Proc . EPAC 2000, Vienna, Austria, p. 2058'

[8] A. Letchford et al., Proc . PAC 99, New York, USA, p. 1767[9] A. Letchford, 'The ESS 280 MHz RFQ Design', in ESS

rep., ESS 99-99-M-2, Dec 1999[10] M. Pabstet al ., Proc. PAC 97, Vancouver, Canada, p.1846[111 M. Ikegami, Phys .Rev. E 59, p . 2330,1999[12] K . Bongardt et al., Proc . EPAC 2000, Vienna, Austria, p .

915

Abstract

BEAM LOSS STUDIES FOR HIGH POWER PROTON DRIVERS

K. Bongardt, M. Pabst, Forschungszentrum Jülich GmbH, GermanyA. Letchford, RAL, Didcot, U.K.

Proton drivers with 5MW average beam power are neededforshortpulse spallationneutron sources as well asforneu-trino factories . The main design goal is to avoid activationat the linac end and to guarantee loss free ring injection af-terwards . Particle loss is caused by the development of ahalo around the dense beam core. Only particles with largeamplitudes in real space can cause activation . Loss freering injection however requires at the linac end very lim-ited energy and phase fluctuation of the bunch center andan unfilamented 6d phase space distribution .Numerical results are presented for noticeable mismatch

later on caused by correlated field errors forbunched beamsin periodic focusing channels . Monte Carlo simulationsareshown for the 214mA ESS linacby assuming amatched in-put distribution, but f1% correlated field errors at 70 MeVfor a limited number ofperiods . Clearly visible is then atthe 1334 GeV final energy more than 10% mismatch of all3 beam radii, modest halo formation and quite large shiftin energy and phase of the bunch center. .

For a space charge effected, but not dominated linac de-sign, the single particle amplitude is limited to twice theinitialmismatched core size. But inphase space single par-ticles can have values above 40 * cans for 30% mismatchof an unfilamented beam at the entrance of the high energylinac section . This case represents halo formation causedby current fluctuations and accumulated field errors.

I BEAM LOSS BYEXCITING A90°RESONANCE DUE TO CORRELATED

FIELD ERRORS

Particle loss is caused by the development of a halo aroundthe dense beam core, driven by mismatch, high spacecharge and temperature anisotropy. For realistic particledistributions with nonlinear space charge forces, particlesinside the beam core can have different tunes . Parametricparticle-envelope resonances can occur between the singleparticle tune and the frequency ofthe mismatched oscillat-ing beam core [1] .In a periodic focusing channel additionalresonances and

instabilities, which don't exist in an uniform channel, caninfluence the single particle motion . The envelope-latticeinstability effects the whole bunch, whereas especially the90° particle-lattice resonance drives single particles eitherto large radial or axial amplitudes . A parametric particle-lattice resonance can be excited either by temperature ex-change or by mismatch [2] .For a space charge effected, but not dominated linac

design with moderate temperature anisotropy, visible halo

formation requires about 30% mismatch ofthe 3 beam radiiif the envelope-lattice instability and either radial or axial90° particle-lattice resonances are avoided . As field errorsare typically atthe % level, it is generally believed thatfielderrors cannot be lead to 30% mismatch of the beam radii .The argument is correct for uncorrelated field errors in anuniform focusing channel. But it is not necessarily validfor correlated field errors in a periodic focusing channel.

In Fig .

I the oscillations of the rms phase width areshown for matched zero current beam in a periodic trans-port charmel with 90.3° longitudinal zero currenttune . Forthe first 40 focusing periods, correlated RF errors of +1 %resp. -1% from period to period are assumed . After 20"superperiods", no error distribution is applied. Clearlyvisible are amplitude modulated phase oscillations with180"lperiod in the error free transport channel above pe-riod number 40 . The phase width differsby more than 10%from its matched input value, compared to about 0.25% asexpected from an uniform focusing channel with 1% fielderror. The reason is the enforced superperiodwith its about180 0 longitudinal zero current tune. Having +1% resp. -1% field error fromperiod to period in an uniformfocusingchannel, these superperiod channel is unstable for an errorfree longitudinal zero current of90° f0.3° .

b

20 40 60 80 10D 120

Peru

140 160

Figure 1 : Phase oscillation fora matched zero current beamwith (+1%,1 %) correlated RF-errors over 40 periods

In Fig. 2, 2d projections of a matched 214 mA bunchedbeam are shown after 160 focusing periods again by as-suming correlated RF errors of +1% resp . -1% from pe-riod to period for the first 20 superperiods. The transversezero current tune is 92° . The resulting maximal transversebeam radii are greater than 3 times the initial ones, whereasthe maximum phase width is only 1 .5 times the initial one.Both transverse phase planes show a small beam core sur-rounded by many halo particles. In the longitudinal phaseplane however the initial bunch core is still existing, butfew single particles have an energy spread twice as largethan the maximum initial one. The not shown error free,but by 30% initial mismatched case leeds to very similarparticle distributions after 160 periods (2] .For a high power linac layout the radial and axial zero

current tunes should be below 90° which can result inlow-

.. ._ . ..... .... .. ...:.. .. .. ... ... .. ... .. :

"30 "20 " 10 0 10 20 30

Y (mm,

30~.. ..... .;_ ... .. ... .. .. .....;.. .. . .. .,

20: 4

685:

MAW (deg)

Figure 2 : Particle projections after 160 periods for amatched 214 mA beam with (+1%,-I%) RF - errors

ering the accelerating gradients. In addition there can bean envelope-lattice instability if the mode frequency of thein phase radial-axial high mode is nearby 180° . As a ruleofthumb, also the envelope-lattice instability is avoided bychoosing the radial and axial zero current tunes below 90°each.

2 HALO FORMATION BY EXCITING A600 RESONANCE DUE TO

CORRELATED FIELD ERRORS

Inmosthigh intensity linac layouts crossing either the 60°transverse or longitudinal zero current tune value cannotbe avoided. By assuming a correlated field error sequenceof ( +1%, 0%, -1% ) resp. from period to period, such asuperperiod will lead to halo formation, but the maximalsingle particle amplitudes are limited here .

In Fig. 3 the rms radius in y-direction and the phasewidth are shown for a matched zero current beam in a pe-riodic focusing channel by assuming ( + 10%, 0%, - 10%RF field errors for 10 superperiods. The transverse resp.

longitudinal zero current tunes are 60 .4° resp. 59.960 . Af-ter 30 periods both shown radii oscillate with 1200 /period .The radial oscillations are caused by the radial defocusingpart ofthe RF field . Both beam radii are increased by about50% in the 10 superperiods .

In Fig . 4 y-rms radii oscillations are shown for beamsby assuming ( +1%, 0%, -1% ) quadrupole field errors for10 superperiods either for a matched zero current or a fullcurrent beam. The zero current beam is the same as ofFig 3 . The transverse focusing period consists of a longRF section, followed by a short doublet connected to onepower supply. For the zero current beam, the by ( +1%,0%, -1% ) doublet errors caused radial oscillations looksvery much the same as the in Fig. 3 shown oscillationscaused by ( +10%, 0%, -10%) RF field errors .The full current beam has equal transverse and longi-

tudinal temperatures and very moderate tune depressions.The in phase high mode frequency is 1160 for the error

r 2C

Y0

g10

6EE014

m¬ 2

6EE~4

12

Y 00

$s

4

32nE¢0

ALIIILIIILfL1A![190r111rlgllqlll;,ID1~IIllILIHliflllllllll"Illiplllll

0 20 W 00 W 100 120 1W 160

Period

20 40 60

0 20 40 60 60 100 120 140 1W

Period

Figure 3 : Beam radii oscillation for a matched zero currentbeam with (+10%, 0%, -10%) RF - errors

'.'.Riinlll111QI111111Td11j1.11t11111tR~l~110110111TiIITITII r15d19r1Ur1r1rlr1rlUgUr1

ero curce

W 100 120 140 160

Period

,rlil9

20 40 W 40 100 120 140 160

Period

Figure 4: Transverse oscillations for a matched zero andfull current beam with (+1 %, 0%, -1%) doublet - errors

free case. The by ( +1 %, 0%, -1 % ) quadrupole field errorscaused radial oscillations, again with about 1200/period,looks very much the same as the for the zero current beamcase . For a zero current beam, quadrupole field errors can-not cause any kind of longitudinal phase oscillations. Fora full current bunch however, there exists a pure transversequadrupolar eigenmode [3], but its required equal ampli-tude and out of phase oscillation cannot be fulfilled by adoublet connected to one power supply only. After about60 focusing periods all 3 rms radii are oscillating in phasewith about 20% amplitude and 1200/period, as expectedfor the in phase radial-axial high mode, see Fig . 4 and Fig .5 . Due to the modest tune depressions ofonly 0.86, no haloformation is caused by these 20% beam radii oscillation .

0 20 40 60 so 101) 120 uo 160Period

0 0

Figure 5: Resulting phase oscillations forthe same full cur-rent beam as before

3 MONTE CARLO SIMULATIONS OFTHE ESS LINAC

All the results above are for a bunched beam transfer linewithout acceleration. The conclusions are also valid forthe design of a high current linac. The difference is thecrossing of dangerous particle-lattice resonances, but withtune depressions as small as 0.7 .As an example 10000 particle Monte Carlo simulations

results are shown for the 214 mA ESS 700 MHz coupledcavity linac which accelerates the beam from 70 MeV upto 1334 GeV [4] . The ratio between full and zero currenttunes is greater than 0.7 both transversely and longitudi-nally. The ESS linac consists out of 132 focusing periodswhere a long RF section is followedby a short doublet con-nected to one power supply. The transverse zero currenttune is 92° at injection and decreases below 60° above 230MeV For the error free matched case there are no parti-cles outside 15 * e,, at the linac end [2] . The maximumsingle particle amplitude is limited to 2 times the initialmismatched core size even for 30% mismatch at 70 MeV[5] .

In Fig. 6 the y-rms radii along the ESS linac are shownfor the error free case and by assuming ( +1%, 0%, -1% )quadrupole field errors forthe first 10 superperiods from70MeV to 322 MeV on . Atthe ESS linac end about 10% radiioscillations are excited compared to the error free case .Modesthalo formation is the consequence : there are about10-3 particles outside 15 * erm, at the linac end.

6

E4

0-

1-- i

0 200 400 600 800 1000 1200

Energy(MA

1400

200 400 600 800 1000 1200 1400

Energy (MOV)

Figure 6 : Rms beam radius along the ESS linac for the

matched case (upper graph) and by assuming ( +1 %, 0%,

-1%) doublet- errors (lower graph)

In Fig . 7 the energy and phase oscillation of the bunch

center are shown by assuming ( +1%, 0%, -1% ) RF field

errors for the first 10 superperiods from 70 MeV to 322

MeV on . The by 10 superperiods caused energy and phase

shift at the linac end is about the same as the rms values

of distributions obtained by doing many calculations with

f1% and f 1° uncorrelated RF errors .For a space charge effected, but not dominated linac de-

sign with moderate temperature anisotropyandby avoiding

ö5

0

s 0

s -50

m 65

~rr200 40o 6o0 wo 1000 1200 1400

Energy (MOV

FA A_A . ...ITV V .

1V

V-

19 -050 200 4w 600 Wo 1000 1200 1400

Enwoy(M6V)

Figure 7 : Energy and phase oscillation of the bunch centercaused by ( +1%, 0%, -1 %) RF - field errors

lattice resonances and instabilities, the single particle am-plitude is limited to twice the initial core size for up to30%mismatch ofan unfilamented beam. Similar results are ob-tained by particle - core simulations of do beams in a peri-odic quadrupole focusing channel [6] . But in phase spacemore than 10-3 particles can be outside 20 * e,.m, going upin phase space above 40 * cm,, [2]. These halo formationespecially in the longitudinal plane can cause activation offollowingcompressor rings .

The halo formation caused by current fluctuation, fila-mented RFQ output distribution and accumulated field er-rors can be represented by 30% mismatch of an unfila-mented beam at the entrance of the error free high energylinac section. By exciting separately all 3 bunched beameigenmodes with its different amplitude ratios, the maxi-mum halo formation is similar to one obtained from manydifferent runs with errors . But the bunch center is shiftedin energy and phase due to RF field effors, which has to

be considered by reducing the energy spread before ring

injection . For the layout of the ESS linac to ring transfer

line, there are less than 10-4 particles outside f2 MeV af-

terbunch rotation, includinghalo formationcausedby 30%mismatched at 70 MeV and f4 MeV resp. f6° final shift

of the bunch center [5] .

4 REFERENCES

[1] A. V Fedotov, R. L. Gluckstem, Prcc. PAC 99, New York,

USA, p. 606[2] A. Letchford et al., Proc. PAC 99, New York, USA, p.1767

[3] M.Pabst at at., Proc . EPAC 98, Stockholm, Sweden, p.146

[4] "The European Spallation Source ESS Study", Vol. 1-3,

March 1997

[5] K. Bongardtet al., 'High Intensity H- Injector Linacs', ESS

rep . 99-100-L, Nov . 99

[6] M. Ikegami, Phys . Rev.E59, p. 2330,1999

198

V. Technical Developments

11 . ELECTRONICS,SEMICONDUCTOR DETECTORS

11 . ELECTRONICS,SEMICONDUCTOR DETECTORS

In the IKP-electronics laboratory activities were carriedout for the COSY-region, here especially for the diagnosticinstrumentations at COSY and the beamlines, and for thenuclear experiments with COSY-beam as well as externalexperiments at CERN and PSI . Among them were devel-opments of electronic systems and devices, which are notcommercially available, electronic support during runningexperiments, consultation and assistance for physicists, andcommon services like repairs, purchase and storage ofelectronic devices and components . Some of the develop-ments were carried out in collaboration with theCOSY-diagnostic group . In the following the representa-tive activities are listed and briefly described .

Electronics

J . Bojowald, H. Labus, E. Br6kel, C. Berchem, N. DoYus, W. Ernst, G . Lürken, R. Nellen

Activities for COSY:The spill detector based on coincident data processing fromtwo adjacent photo multiplier tubes with plastic scintillatorshas been further developed and is now ready for the firstonline tests . It allows absolute intensity measurements ofextracted beams within a wide range of intensity from some10^3 Hz to 10^12 Hz at stochastic extraction and even ofpulses from kicker extraction where rates of 10^11/us canoccur . Energy calibration can be performed on line fordifferent particles and energy . The large intensity region isachieved by switching light filters within a gap betweenscintillators and photo cathodes, or the high voltage of thephoto multipliers or the gain ofthe electronic preamplifiers.As an additional device an ionization chamber is mountedbetween the two photo multipliers whose electrode consistsofsix pixels, fore inner circle segments and two outer rings,each connected to a I/U-converter with switch selectablesensitivity . This allows a rough profile measurement andcan be used as an additional and independent device tocalibrate the intensity measurements on line . The detectoris mounted in a steel pot of at least 92mm inner diameterwhich in this case can be connected to an CF100 cylindervia a bellow and can be moved pneumatically to and fromthe measurement position within <5s . Thus the detectorworks at normal air which is a great advantage concerningcosts and services especially with large UHV-facilities . Thewall of the steel pot is no real disadvantage. The thicknessof the steel is lmm but can be made 0.lmm around thesensitive area of the detector so even protons with energydown to 50 MeV can be detected without significant profiledistortion. Principally distortion cannot be avoided withextracted beams which normally have non periodic timestructure and thus can not be detected with non disturbingdevices as BPMs or WCMs which need a pulsed beam. Thefirst signal conditioning is done in a local preamplifier witha fast coincidence channel for absolute particle counting atrates up to 10^6 Hz, a fast 100 MHz ADC to analyse thekicker pulses and a slow amplifier to measure the anodecurrent i .e . the spill of one photo multiplier at normal ex-traction. The second signal conditioning is done within asmall crate mounted on the top of the steel pot containingdigital and analogue I/O boards and a local controller whichperforms basic operations like offset corrections and time

averaging . Raw data are then transmitted via a serial RS-485 bus to a PC where a live display and a control systemdeveloped with LABVIEW 5.1 . will complete the system .Spill and profile can be displayed simultaneously every 100ms. Along the beam lines position and type of every in-stalled detector can be identified.

Three of the fifteen MWPC profile monitors have beenequipped with additional ionisation chambers with a com-plete new design replacing the old prototypes . The newchambers need no external power supply or high voltageand have a differential output ( sensitivity : I V per 10^9protons/s at 1 GeV, risetime : 25 ms ) which eliminates dis-tortions from ground loops along the 100m distance to theCOSY control room .

The new Schottky Pickups with split electrodes were testedin the laboratory and installed in the COSY ring . Firstmeasurements have been performed successfully .

Activities for the experiments :At the PSI the crystal spectrometer has been reinstalled inthe measurement area. Several additional sensors andmonitor functions were implemented and the existingLABVIEW control software has been extended. Some per-turbations within the signal processing could be eliminated .A complete revision ofthe existing documentation has beencarried through.

Design and marketing analyses for the Straw Detector frontend signal processing were made and first tests of pre-amplifiers were carried through with very challenging spa-tial and thermal restrictions .

At CERN the IKP part of the ATRAP Experiment (details

see Annual Report 1999) was set into operation successfully

at the AD facility . Designs for the next steps were per-

formed.

Measurement standards for testing the MWPC detectors of

the ANKE Experiment have been developed and two fur-

ther detectors were equipped with read out electronic and

set into operation .

For the GEM experiment a new front end signal processing

electronic was designed in collaboration with the KFKI

Budapest and the University of Sofia .

Different from previous years the main activities in thelaboratory were devoted to development of position sensi-tive Si(Li)-detectors, up to 7 mm thick, for the ANKE sili-con strip vertex detector and preparations for connectingvarious silicon detectors to readout systems based on chipelectronics. Position sensitive Si(Li)-detectors with strips onthe boron-implanted entrance contact have been producedin the laboratory and used since many years, for example at

H2 -studies [1,2], diagnosis of the external COSY beam [3]

and as a part of the spectator detector system [4,5] . Roughstructure on the about 0.5 mm thick Li-diffused contact, forexample 2 mm wide strips, could be realized by cutting thegrooves . But this technique could not be applied for finer orcurved structures . Therefore a lot of effort was spent toproduce only - 50 pm thick Li-diffused layers and ~ 50 pindeep plasma etched grooves not wider than 50 pim neededfor fine structured two-dimensional Si(Li)-detectors .Several methods to diffuse lithium into silicon at tempera-tures as low as possible were examinated . The resultedlithium distributions were measured through successivelapping of diffused layers . Up to now the best results wereachieved with saturated LJAlH4-solution painted on siliconsurface. At temperatures of about 500 K we producedhomogeneous, 50 pm thick Li-diffused layers on severalslices with a diameter of 77 mm. This layers are the n-con-tact of the diodes which are now in preparation . One ofthem has already position sensitive structure on the n-con-tact: 50 strips with a pitch of 1 mm, separated by 40 Rmdeep and 60 p.m wide grooves . The grooves were definedby photolithography and made by etching in gaseous SF6-plasma . Since the depth ofthe grooves is slightly below thethickness of the Li-layer the electrical separation of thestrips is not perfect (- 0.2 MQ) but still enough for positionreadout by means of a resistor chain . Additional Li-driftcould help to increase the resistance between the strips .Based on the results achieved during these investigations webelieve that - 250 pm wide strips on - 25 pin thick Li-con-tact will be possible to realize . As the position structure onboth detector contacts will be produced with the help ofphotolithography and plasma etching there is almost nolimitation in the shape ofthe position elements.

A 5.5 mm thick Si(Li)-detector with a diameter of 105 mm,cutted from a new silicon ingot, has been produced to provethe quality of the material. Because of the large diameterseveral modification on the existing apparatus had to bedone and also a new equipment for Li-drift. After successfultests additional slices are ordered from the same ingot forpreparing large two-dimensional position sensitive Si(Li)-detectors (up to 70x70 mm).

Various preliminary developments concerning the con-struction of ANKE vertex detector have been carried out,like printed board feedthroughs and their behavior invacuum, printed leads inside the flexible foils and a testchamber to investigate the thermal behavior of chip elec-

Semiconductor Detectors

G. Fiori, T . Krings, H . Metz, D. Protic

tronics in vacuum . A new bond machine has been installedand taken into operation . Thorough tests were performed toget much skill in bonding needed for connecting the chipswith printed boards and the boards with the strips of posi-tion sensitive detectors .

Because there was no GEM-experiment with germaniumdetectors the activities connected with the detector system"Germanium wall" were much reduced . Further investiga-tions were performed to produce good n+-contacts by ion-implantation . Still existing problem with the conversion ofn-type germanium into the p-type during the annealing ofthe n+-contacts could not be satisfactorily eliminated . Manydiscussions were needed concerning the future use ofsiliconQuirl-detectors at COSY-experiments . An equipment fortesting such detectors has been under construction .

Second position sensitive detector system consisting of twoSi(Li)-detectors has been prepared for the diagnosis of theexternal COSY-beam . Each of the detectors has 1 mm widestrips on an area of 50 x 50 mm2 connected to a printedresistive chain . The together mounted detectors have stripsorientated under right angle . A two-dimensional positioninformation is available by means of a simple readout overthe resistive chains.

First test measurements using the 200 strip germaniumdetector, developed and constructed in collaboration withGSI-Darmstadt [6], were performed in combination withGSI-spectrometer FOCAL (cylindrically curved Si-crystalfor transmission x-ray spectrometry) . An energy resolutionof better than 100 eV [FWHM] at 50 keV was achievedalong with a high detection efficiency. Together with thegood position sensitivity and measured time resolution of70 ns [FWHM] this will be by far sufficient to meet thecriteria of the current x-ray spectroscopy program at thestorage ring ESR at GSI . An already years ago manufac-tured germanium polarimeter (16 position elements, each ofthem with an area of 7x7 mm2 and 10 mm thick) has beenput in working order and prepared for measurements atESR.

For a new collaboration with ITEP-Moscow the develop-ment of a novel type germanium detector with internalamplification has been started . Using such detectors onecould extend the range of energy measurements towards100 eV or even below . Extreme interesting experiments

concerned with neutrino physics could be performed withlarge detectors of this type .

References :[1] Annual Report IKP 1987, All-Spez 442, p . 140[2] Annual Report IKP 1988, Jill-Spez 499, p . 135[3] I. Ilieva, Silicon Strip Detectors for Beam Adjustment atGEM (COSY), Verhandlungen der DPG, Freiburg, 1999

[4] Annual Report IKP 1999, Ril-3744, p . 21[5] ANKE-Collaboration, this Annual Report[6] Annual Report IKP 1999, Jill-3744, p . 196

VI .

Scientific Council COSY

VII .

Program Advisory Committee(for COSY)

VIII . Collaborations

IX. - Personnel

X. Publications

XI .

Index of Authors

VI.

Scientific Council COSY

Prof. Dr . P . Braun-Munzinger (Chairman)Dr. A. BringerProf. Dr . L. CardmanProf. Dr . H. CoenenProf. Dr . J . DomingoProf. Dr . D. DrechselProf. Dr . D. v . HarrachProf. Dr . E. HilgerProf. Dr . Y. NagaiProf. Dr . O . RiskaDr. D. TrinesDr. H. Wenninger

VII. Program Advisory Committee (for COSY)

Prof. Dr . M. GarconProf. Dr. W. GlöckleProf. Dr. E. GrosseProf. Dr. C. GuaraldoProf. Dr. M. HarakehProf. Dr. S. Kullander (Chairman)Prof. Dr. R. LanduaProf. Dr. V. MetagProf. Dr. H.O. MeyerProf. Dr. U. MoselDr. E. RademacherProf. Dr. K. RithProf. Dr. C . Wilkin

GSI DarmstadtIFF, FZ JülichJLab, USAINC, FZ JülichJlab, USAUniversity ofMainzUniversity of MainzUniversity of BonnUniversity of Osaka, JapanUniversity of Helsinki, FinlandDESY HamburgCERN, Switzerland

Saclay, FranceUniversity ofBochumFZ RossendorfINFN Frascati, ItalyKVI Groningen, The NetherlandsUniversity of Uppsala, SwedenCERN; SwitzerlandUniversity of GiessenIUCF Bloomington, USAUniversity ofGiessenCERN, SwitzerlandUniversity ofErlangenUniversity College London, UK

208

VIII. COLLABORATIONS

COSY-EDDA-Collaboration*Spokesmen : J . Bisplinghoff, F . Hinterberger, W. Scobel

R. Gebel, R. Maier, D. Prasuhn, P . v . Rossen :Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

M. Altmeier, J . Bisplinghoff, T. Bissel, M. Busch, R. Daniel, O. Diehl, H.J . Engelhardt, J . Ernst, P.D . Eversheim,O. Felden, R. Gross-Hardt, F . Hinterberger, T . Hüskes, R. Jahn, R . Maschuw, T. Mayer-Kuckuk, H. Rohdjeß,D. Rosendaal, M. Schulz-Rojahn, V. Schwarz, S . Thomas, H.J . Trelle, M. Walker, E . Weise, R. Ziegler:Institut für Strahlen- und Kernphysik, Universität Bonn

F . Bauer, T . Bissel, R. Bollmann, K. Büßer, F . Dohrmann, J. Flammer, M. Gasthuber, J . Greiff, A . Gross,K . Hebbel, I . Koch, R. Langkau, T . Lindemann, J . Lindlein, M. Pfuff, B . Sanz,N. Schirm, W. Scobel, S . Steinbeck,A. Wellinghausen, K. Woller :I . Institut für Experimentalphysik, Universität Hamburg

*supported by

BMFT-Verbundforschung ; University Program of Forschungszentrum Jülich

COSY-11 Collaboration*Spokesman : M. Wolke

D. Grzonka, K. Kilian, W. Oelert, G . Schepers, T. Sefzick, S. Sewerin, M. Wolke :Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

P. Wüstner :Zentrallabor für Elektronik, Forschungszentrum Jülich, D-52425 Jülich

H.H. Adam, A. Khoukaz, N. Lang, T. Lister, C . Quentmeier, R. Santo :Institut für Kernphysik, Universität Münster

L . Jarczyk, P . Moskal, J . Smyrski, A. Strzalkowski:Institute of Physics, Jagellonian University, Cracow, Poland

A. Budzanowski: Institute ofNuclear Physics, Cracow, Poland

P . Kowina, M. Siemaszko, W. Zipper: Institute of Physics, Katowice, Poland

*supported by

BMFT-Verbundforschung; International Bureau ofthe BMBF, DLR-Bonn;

University Program of Forschungszentrum Jülich

COSY-13 Collaboration*Spokesman : B . Kamys

W. Borgs, M.Hartmann, T.Hermes, H.R . Koch, P. Kulessa, R. Maier, H. Ohm, D. Prasuhn,

O.W.B . Schult, J . Stein, H. Ströher:Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

L. Jarczyk, B. Kamys, St. Kistryn, Z . Rudy, A. Strzalkowski :

M.Smoluchowski Institute ofPhysics, Jagellonian University, Cracow, Poland

K. Pysz:H.Niewodniczanski Institute ofNuclear Physics, Radzikowskiego 152, PL-31342 Cracow, Poland

W. Cassing :Institut für Theoretische Physik, Universität Gießen

I.Zychor:Andrzej Soltan Institute for Nuclear Studies, PL-05400 Swierk

M. Matoba, Y. Uozumi :Dept. ofNuclear Engineering, Kyushu University, Fukuoka 812, Japan

*supported by International Bureau of KfK Karlsruhe ; TEMPUS-Program

ANKE* (0°-Facility)Spokesman: K. Sistemich

U. Bechstedt, N. Bongers, G. Borchert, W. Borgs, W. Bräutigam, M. Büscher, J. Dietrich, S . Dymov, D. Gotta, .D . Grzonka, M. Hartmann, V. Hejny, M. Hennebach, H. Junghans, M. Kamadi, V. Kleber, H.R . Koch, K. Kruck,P . Kulessa, H. Labus, I . Lehmann, C. Leim, B. Lorentz, R . Maier, S. Martin, A. Mussgiller, M. Nekipelov,R . Nellen, W. Oelert, H. Ohm, D. Prasuhn, H.J . Probst, D. Protic, F. Rathmann, R. Schleichert, H . Schneider,G . Schug, O.W.B . Schult, H. Seyfarth, A. Sibirtsev, K . Sistemich, H.J . Stein, H. Str6her, K.-H. Watzlawik :Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

G . Hansen, F . Klehr, H . Stechemesser: Zentralabteilung Allgemeine Technologie, Forschungszentrum Jülich, D-52425 Jülich

R. Baldauf, M. Drochner, W. Erven, H . Kleines, H. Loevenich, J. Sakardi, P . Wüstner, K. Zwoll: Zentrallabor fürElektronik, Forschungszentrum Jülich, D-52425 Jülich

M. Debowski, N. Langenhagen, H. Müller, B . Rimarzig, Chr. Schneider:Zentralinstitut für Kernforschung, Rossendorf, D-01474 Dresden

J . Ernst : Institut für Strahlen- und Kernphysik, Universität Bonn, D-53115 Bonn

N. Koch, S . Lorenz, K. Rith, F. Rathmann, F. Schmidt, E . Steffens :Physikalisches Institut II, Universität Erlangen-Nürnberg, D-91058 Erlangen

W. Cassing, : Institut für Theoretische Physik, Universität Gießen, D-35392 Gießen

R . Eßer, H. Paetz gen . Schieck : Institut für Kernphysik, Universität Köln, D-50937 Köln

H.-H . Adam, A. Khoukaz, N. Lang, Th. Lister, C . Quentmeier, R . Santo :Institut für Kernphysik, Universität Münster, D-48149 Münster

L. Jarczyk, B . Kamys, St. Kistryn, Z . Rudy, J . Smyrski, A. Strzalkowski :Institute of Physics, Jagellonian University, Cracow, Poland

K. Pysz: Institute ofNuclear Physics, Radzikowskiego 152, PL-31342 Cracow, Poland

V. Abazov, A. Churin, O. Gorchakov, A. Kacharava, N. Kadagidze, V.I . Komarov, V. Kruglov, A. Kulikov, V.Kurbatov, V. Leontiev, G . Macharashvili, S . Merzliakov, A. Petrus, M. Sapozhnikov, E . Strokovsky, Yu. Uzikov, A.Volkov, S. Yaschenko, B . Zalikhanov, N. Zhuravlev: Joint Institute ofNuclear Research, Dubna, Russia

S . Trusov, V . Yazkov: Dubna Branch ofthe Moscow State University, Dubna, Russia

V . Abaev, S. Barsov, S . Belostotski, O . Grebenyuk, V. Koptev, A. Kovalov, P . Kravtsov, M. Mikirtichyants,S . Mikirtichyants, V . Nelubin, A. Vassiliev : Petersburg Nuclear Physics Institute, Gatchina, Russia

V. Chemetzky, V. Chernyshev, M. Chumakov, P . Fedorets, A . Gerasimov, V. Goryachev, L. Kondratyuk : Institutefor Theoretical and Experimental Physics, Moscow, Russia

Ye.S . Golubeva, V. Grishina : Institute for Nuclear Research, Russian Academy of Sciences, Moscow, RussiaC . Wilkin : Physics Department, Univ. College London, London WC1 6BT

N. Amaglobeli, B . Chiladze, M. Nioradze : High Energy Physics Institute, Tbilisi State University, Tbilisi, GeorgiaI . Zychor: Soltan Institute for Nuclear Studies, PL-05400 Swierk, Polen

*supported by

Land Nordrhein-Westfalen, BMFT (Verbundforschung ; Forschungszentrum, WTZ mit Polen undRussland), DFG, INTAS, Collaborators

COSY-GEM-Collaboration*Spokesman : H . Machner

S. Abdel-Samad, J. Bojowald, D. Filges, K . Kilian, R. Klein, Th . Krings, H . Machner, A. Magiera, R . Maier,D. Protic, P . v. Rossen:Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

K. Zwoll :Zentralinstitut für Elektronik, Forschungszentrum Jülich, D-52425 Jülich

J . Ernst, R . Jahn, J . Urban:Institut fir Strahlen- und Kernphysik, Universität Bonn

D. Frekers :Institut für Kernphysik, Universität Münster

P . Hawranek, L. Jarczyk, S . Kistryn, W. Klimala, J . Smyrski, A. Strzalkowski, A . Wronska:Jagellonian University, Cracow, Poland

A. Budzanowski, L . Freindl, S . Kliczweski, R . Siudak : Institute ofNuclear Physics, Cracow, Poland

H.S . Plendl : Physics Department, FSU, Tallahassee, Florida, USA

B.J . Lieb : Physics Department, GMU, Fairfax, Virginia, USA

L.C. Liu: LANL, T. Division, Los Alamos, USA

H. Nann: IUCF, Bloomington, Indiana, USA

A. Chatterjee, B.K . Jain, S.S. Kapoor, B.J. Roy :BARC Trombay, Bombay, India

J . Ilieva, T . Kutsarova, E . Pentchev: Institute ofNuclear Research and Nuclear Energy, Sofia, Bulgaria

S . Förtsch: National Accelerator Centre, Faure, South Africa

D . Kolev. R. Tsenov : Univ. Sofia, Sofia, Bulgaria

G . Martinska, M. Ulicny : P . J . Safarik Univ., . Kosice, Slovakia

M. Kracikova : Technical Univ. Kosice, Kosice, Slovakia

L . Golovanov, D. Kirillov, L. Sitnik, N. Piskunov : Laboratory for High Energies, JINR Dubna, Russia

*supported by BMFT-Verbundforschung ; University Program ofForschungszentrum Jülich; International Bureau

ofthe BMBF, DLR-Bonn

COSY-TOF Collaboration*Coordinator : E . Roderburg

S. Abdel-Samad, M. Abdel-Bary, D. Filges, A. Gillitzer, H. Hadamek, , D . Hesselbarth, U. Johnen, K. Kilian,R . Klein, S . Marwinski, H.P . Morsch, N. Paul, E. Roderburg, T . Sefzick, H . Uehlemann, P. Wintz :Institut für Kernphysik, Forschungszentrum Jülich GmbH, D-52425 Jülich

H . Kämmerling: Zentralabteilung Technologie, Forschungszentrum Jülich GmbH, D-52425 Jülich

M. Drochner, P . Wüstner: Zentrallabor für Elektronik, Forschungszentrum Jülich GmbH, D-52425 Jülich

H. Koch, S . Mauro, W. Meyer, A. Wilms:Institut für Experimentalphysik, Ruhr-Universität Bochum, D-44780 Bochum

H. Dutz: Physikalisches Institut der Universität Bonn, D-53115 Bonn

K.-Th.Brinkmann, H. Freiesleben, B. Jakob, L. Karsch, E. Kuhlmann, Ch. Plettner, P . Sch6nmeier, M. Schulte-Wissermann, G .Y . Sun, M. Würschig-Pörsel :T.U . Dresden, D-01062 Dresden

M. Müller-Veggian: Fachhochschule Jülich

H. Clement, E . Dorochkevitch, J . Kress, G .J . Wagner, G. Zhang .Physikalisches Institut, Universität Tübingen, D-72076 Tübingen

S . Dshemuchadse, K. Möller, L. Naumann, A. Schamlott:Institut für Kein- und Hadronenphysik, FZ Rossendorf, D-01314 Dresden

W. Eyrich, M. Fritsch, J. Georgi, H . Mörtel, W. Schroeder, F . Stinzing, M. Wagner, S . Wirth :Physikalisches Institut, Universität Erlangen-Nürnberg, D-91058 Erlangen

A. Filippi, S. Marcello : INFN Torino, Italien

P . Zupranski : Soltan Institut for Nuclear Studies, Warsaw

*supported by

BMFT-Verbundforschung ; University Program ofForschungszentrum Jülich GmbH

COSY-MOMO-Collaboration*Spokesman : R . Jahn

H. Machner, P . v . Rossen, R . Tölle : Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

F . Bellemann, A. Berg, J . Bisplinghoff, G. Bohlscheid, J . Ernst, F . Hinterberger, R. Ibald, R. Jahn, R . Joosten,R. Maschuw, T. Mayer-Kuckuk, G. Mertler, J . Munkel, D. Rosendaal, H. Schnitker :Institut für Strahlen- und Kernphysik, Universität Bonn

P. v . Neumann-Cosel : Institut flr Kernphysik, Technische Hochschule Damstadt

L . Jarczyk, A . Magiera, J. Smyrski, A . Strzalkowski:Institute for Physics, Jagellonian University, Cracow, Poland

A. Kozela : University ofCracow, Poland

C. Wilkin : University of London, England

*supported by BMFT-Verbundforschung ; University Program ofForschungszentrum Jülich ;

NESSI Collaboration (European Spallation Source (ESS))*Spokesman: U. Jahnke

D. Filges, F. Goldenbaum, R.D. Neef, K . Nünighoff, N. Paul, H . Schaal, G . Sterzenbach, A . Tietze,M. Wohlmuther:Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

M. Enke, C.-M. Herbach, D. Hilscher, U . Jahnke, V . Tishchenko :Hahn-Meitner-Institut Berlin, Glienickerstr. 100, D-14109 Berlin

A . BShm, J . Galin, A. Letourneu, B . Lott, A . PdghaireGANIL (IN2P3-CNRS, DSM-CEA), BP 5027, F-14076 Caen-Cedex, France

L. Pienkowski : University of Warsaw, P1-02-097 Warszawa, Poland

W.U . Schr6der, J. T6ke: University ofRochester, Rochester, New York 14627, USA

*supported by

EU-TMR-Program and Helmholtz Strategiefonds

JESSICA-Collaboration*Spokesman : H. Tietze-Jaensch

H. Conrad, J. Dietrich, D. Filges, F. Goldenbaum, G. Hansen, H. Klein, S . Martin, R.D . Neef, K. Nünighoff, N . Paul,Ch . Pohl, D . Prasuhn, H. Schaal, H. Stelzer, H. Tietze-Jaensch, H . Ullmaier:Forschungszentrum Jülich, D-52425 Jülich

E . Iverson, P.K. Job : Argonne National Laboratory (USA)

B. Haft, W. Nienhaus, E. Schachinger: Techn. Univ . Graz (Austria)

Y . Oyama, N. Watanabe : JAERI (Japan)

M. Furusaka : KEK (Japan)

A.V . Belushkin, A. Smirnov, V. Soukhanov: FLNP, JINR, Dubna (Russia)

P . Ferguson, E. Pitcher, G . Russell : Los Alamos National Laboratory (USA)

T . Gabriel, T . Lucas: Oak Ridge National Laboratory (USA)

G.S . Bauer, H. Spitzer : Paul Scherrer Institut (Switzerland)

S.M. Bennington, T . Broome, H . Jones : RAL (UK)

Y. Kiyanagi : University of Hokkaido (Japan)

*supported by

EU-TMR-Program, Helmholtz Strategiefonds

PISA Collaboration*Spokesmen: B . Kamys and F . Goldenbaum

D. Filges, F . Goldenbaum, K. Kilian, P . Kulessa, H. Machner, R.-D . Neef, H. Ohm, N. Paul, H . Schaal :Institut für Kernphysik, Forschungszentrum Julich, D-52425 Jülich

M. Beyss, H. Ullmaier: Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich

A.Heczko, L. Jarczyk, B . Kamys, St . Kistryn, W. KIimala, A. Magiera, J . Majewski,W. Migdal, Z . Rudy,J . Smyrski :M. Smoluchowski Institute ofPhysics, Jagellonian University, PL-30059 Krak6w, Poland

A. Budzanowski, M. Kistryn, St . Kliczewski, K.Pysz, R . Siudak :H. Niewodniczanski Institute ofNuclear Physics, PL-31342 Krak6w, Poland

R. Barna, V. D'Amico, D. De Pasquale, A. Italiano :Dipartimento di Fisisca, Messina University and Institüto Nazionale di Fisisca Nucleare, Sezione di Catania, GrupoCollegato di Messina, I-98166 Vill . 'S . Agata (Messina), Italy

A. Bubak, J . Kisiel, E . Stephan, W. Zipper: Institute of Physics, University of Silesia, PL-40007 Katowice, Poland

S . F6rtsch, D . Steyn : National Accelerator Centre, PO Box 72, Faure, 7131 South Africa

J . Cugnon: Institut de Physique, Universite de Liege, B-4000 Liege, Belgium

P.L . Biermann : Max-Planck-Institut für Radioastronomie, D-53121 Bonn, Germany

*supported by BMFT-Verbundforschung, EU-TMR-Program

PROMICE/WASA Collaboration*Spokesmen : B . Höistad and S . Kullander

H. Calen, S . Carius, S . Dahigren, K . Fransson, L . Gustafsson, S . Haggstr6m, B . Höistad, A. Jansson, T. Johansson,S . Küllander, J . Moehn, A. M6rtsell, R. Rüber, H. Rubinstein, U . Schüberth :Department of Radiation Sciencves, Uppsala, Sweden

K. Kilian, W. Oelert, T . Sefzick :Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

Z . Wilhelmi, J . Zlomanczuk:Institute of Experimental Physics, Warsaw, Poland

Z . Zabierowski :Institute ofNuclear Studies, Lodz, Poland

A. Kupsc, A. Nawrot, J . Stepaniak:Institute for Nuclear Studies, PL-00681 Warsaw, Poland

A. Bondar, A. Chilingarov, P . Gaidarev, G. Kolachov, A. Kuzmin, B . Shwartz, V. Sidorov :Institute ofNuclear Physics, Novosibirsk, Russia

Z . Pawlowski :Institut of Radioelectronics, Warsaw, Poland

D. Bogoslawsky, V. Dunin, B . Morosov, A. Povtorejko, S . Sandukovsky, A. Sukhanov, V. Tikhomirov :Joint Institute for Nuclear Research Dubna, 101000 Moscow, Russia

A. Bolozdynia, A. Martemyanov, V . Sopov, V. Tchernyshev:Institut of Theoretical and Experimental Physics, Moscow, Russia

H . Hirabayashi, A. Yamamoto :National Laboratory for High Energy Physics, Tsukuba, Japan

B. Chernyshev, M. Gornov, Y. Gurov, V. Saveliev, R. Shafigullin :Moscow Engineering Physccs Institute, Moscow, Russia

C . Ekström, A. Johansson, D . Reistad :The Svedberg Laboratory, Uppsala, Sweden

B. Trostell :The Studsvik Neutron Research Laboratory, Studsvik, Sweden

L . Bergstrom :Department of Physics, Stockholm University, Sweden

H . Shimitzu :Department ofPhysics, Yamagata University Japan

H. Ikegami, Y. Mizuno :Research Center for Nuclear Physics, Osaka, Japan

AD-2 Collaboration (ATRAP)*Spokesman : G. Gabrielse

G . Gabrielse, T. Roach, J . Estrada, D. Hall, P . Yesley :Department ofPhysics, Harvard University, Cambridge, MA 02138, USA

H. Kalinowsky : Univ. Bonn, ISKP, D-53115 Bonn

T.W . Hänsch, K. Eikeman, J . Walz: Max-Planck-Institut für Quantenoptik, D-85748 Garching

W. Oelert, D . Grzonka, G. Schepers, T. Sefzick:Institut fir Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

T. Hijmans : Dept . of Physics, Univ . of Amsterdam, NL-1018 XE, The Netherlands

W.D. Phillips, St.L. Rolston : National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

J . Walraven: FOM Institute for Atomic and Molecular Physics, 100 DB Amsterdam, The Netherlands

W. Jhe : Department ofPhysics, Seoul National University, 151-742 Korea

D. Wineland, J . Bollinger : National Institute of Standards and Technology, Boulder, CO 80303, USA

W. Breunlich : Institute for Medium Energy-Physics ofthe Austrian Academy ofSciences, A-1090 Wien

*supported by

BMFT-Verbundforschung, National Science Foundation (USA)

ZEUS CollaborationSpokesman : R . Manner, Deutsches Elektronen-Synchrotron (DESY), D-22603 Hamburg

D. Filges, R.D . Neef:Institut fir Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

and 49 national and international institutions

EUROBALL-Collaboration

R.M . Lieder: Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich

P . von Brentano : Institut für Kernphysik, Universität zu Köln, D-50937 Köln

D. Schwalm: MPI fitr Kernphysik Heidelberg, Postfach 103980, D-69029 Heidelberg

J. Gerl : GSI Darmstadt, Postfach 110552, D-64291 Darmstadt

H. Hubel: Institut für Kernphysik, Universität Bonn, D-53115 Bonn

K.P . Lieb : II . Physikalisches Institut, Universität Göttingen, D-37073 Göttingen

F . D6nau: Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, D-01314 Rossendorf

J . Lisle : Department of Physics, Victoria University ofManchester, Manchester M13 9PL, UK

P. Nolan: Department ofPhysics, Univ . ofLiverpool, Liverpool L69 3BX, UK

J . Simpson : Daresbury Laboratory, Warrington WA4 4AD, UK

C. Rossi-Alvarez : Istituto Nazionale di Fisica Nucleare, Padova, I-35131 Padova, Italy

G . deAngelis : Istituto Nazionale di Fisica Nucleare, Lab . Nazonali di Legnaro,1-35020 Legnaro, Italy

M. Pignanelli : Istituto Nazionale di Fisica Nucleare, Sezione di Milano, I-20133 Milano, Italy

C. Fahlander: Department of Physics, University ofLund, S-22362 Lund, Sweden

A. Johnson : Manne Siegbahn Institute of Physics, S-10405 Stockholm, Sweden

J . Nyberg : The Svedberg Laboratory, S-75121 Uppsala, Sweden

B. Herskind: NBI, University ofCopenhagen, DK-1350 Copenhagen, Denmark

F. Beck: ihres Strasbourg, F-67037 Strasbourg, France

F . Hannachi, Institut de Physique Nucleaire, CSNSM, F-91405 Orsay, France

TMR Gamma-Tracking Detector CollaborationCoordinator : R.M. Lieder

R.M . Lieder, W. Gast, H.M . Jäger, L . Mihailescu, M. Rossewij :Institut für Kernphysik, FZ Jülich, D-52425 Jülich, Germany

J . Eberth, G. Pascovici, H.G . Thomas, D . Weisshaar :Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany

F . Beck, D. Curien, G. Duch6ne, E. Pachoud, I . Piqueras :lReS Strasbourg, F-67037 Strasbourg, France

C. Rossi Alvarez, D . Bazzacco, M. Bellato, Th. Kroell, Ch . Manea, B . Quintana, R . Venturelli :INFN, Sezione di Padova, I-35131 Padova, Italy

D.R . Napoli, D. Rosso, P . Spolaore :INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy

A . Geraci, A. Pullia, G . Ripamonti :Dip . Elettronica e Imformazione, Politecnico di Milano,1-20133 Milano, Italy

F . Camera, S . Leoni, B . Million, O. Wieland, A. Bracco, M. Pignanelli, S . Brambilla :

INFN, Sezione di Milano, I-20133 Milano, Italy

J . Lisle, A.G . Smith, R . Well :Schuster Laboratory, University ofManchester, Manchester M13 9PL, UK

P. Nolan, A. Boston, D. Cullen, M. Descovich, T . Enqvist :Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 3BX, UK

B. Cederwall, E. Ideguchi, J . van der Marel :Department of Physics, Kungliga Tekniska Högskolan Stockholm, S-100 44 Stockholm, Sweden

J . Nyberg:Department of Neutron Research, Uppsala University, S-75120 Uppsala, Sweden

B. Herskind, G. Sletten, J . Wilson:Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark

B . Redouin, R. Henck, D. Gutknecht, K . Jääskeläinen :

Eurisys Mesures, F-67834 Tanneries, France

218

IX.

PERSONNEL

Dr. F . Grümmer (TH)

Dr . D . Grzonka (E1)Scientific Staff:

Dr. J . Haidenbauer (TH)Prof. Dr . G . Baur (TH)

(Priv . Doz . at the Univ. Graz)(a.o . Prof. at the Univ. Basel)

DP V. Baru (TH)Dr . T . Hemmert (TH)

Dr. U. Bechstedt (LI)

(until September 30, 2000)

Dr. J . Bojowald (Ec)

DI. K. Henn (LI)

Dr. K . Bongardt (LI)

Dr. D. Hesselbarth (E1)

Prof. Dr. G. Borchert (E2)(apl . Prof. at the Univ . Köln)

DI . W. Bräutigam (LI)

Dr. M. Büscher (E2)

Dr. P . Büttiker (TH)

Dr. habil . J . Dietrich (LI)

Dr . A . Djaloeis (E1)

DP S. Dymov (E2)

Dr E . Epelbaum (TH)

Prof. Dr. Ch. Elster (TH)

Dr. O . Felden (L1)

Dr . N . Fettes (TH)(until November 30, 2000)

Prof. Dr . D . Filges (E1)(apl . Prof. at the Univ . Wuppertal)

M. Frink (TH)(since October 3, 2000)

DP A. Gasparian (TH)

Dr . W. Gast (E1)

Dr. R . Gebel (LI)

Dr. G. Gellas (TH)(until May 25, 2000)

Dr . A . Gillitzer (EI)(Priv. Doz. at the Univ. Bonn)

Dr . M. Glende (LI)(since March 1, 2000)

Dr. F. Goldenbaum (E1)

Dr . D. Gotta (E2)

219

Dr. V. Hejny (E2)

DP M. Hennebach (E2)

I . Ivanov (TH)

Dipl . U . Johnen (E1)since Oct. 1, 2000

Dr . H.U. Junghans (E2)(until October 31 st, 2000)

Dr. H . Kamada (TH)(from May 1 to October 31, 2000)

Prof. Dr. K . Kilian (El)(Prof, at the Univ . Bonn)

DP V. Kleber (E2)(since February 1st. 2000)

Dr. V . Klemt (TH)

Dr. R . Koch (E2)

Prof. Dr. S . Krewald (TH)(apl. Prof. at the Univ . Bonn)

DP H. Krebs (TH)

DP B. Kubis (TH)(since January 15, 1999-11-23)

Dr. P . Kulessa (E2)

Dr. H . Labus (Ec)

H.R. Langohr (E 1)

Dr. H. Lawin (LI)

Dr . A. Lehrach (LI)

DP I . Lehmann (E2)

Ch. Leim (E2)(since June 5, 2000)

Prof. Dr. R.M. Lieder (EI) Dr . M . Rogge (El)(apl . Prof. at the Univ . Bonn) until June 30, 2000

Dr . B . Lorentz (LI) Dr. P . von Rossen (LI)

Prof. Dr. H . Machner (E1) DP S.M. Abd El Samad (E1)(Honorar Prof. at the Univ . Essen) (NRC, AEA, Egypt)

Prof. Dr . R . Maier (LI) F . Sassen (TH)(Prof. at the Univ. Bonn) (since July 1, 2000)

S . Marwinski (E1) Dr. H . Schaal (E1)from Oct . 1 until Nov. 30, 2000

Dr . W. Schäfer (TH)Dr. S . Martin (LI)

Dr . G . Schepers (E1)Prof. Dr. Ulf-G. Meißner (TH) since May 1, 2000(apl . Prof. at the Univ . Bonn)

Dr. R . Schleichert (E2)Dipl . S. Menzel (E 1)until March 31, 2000 Dr.-Ing. A. Schnase (LI)

DP L. Mihailescu (E1) DI . H . Schneider (LI)until Nov . 16, 2000

S . Schneider (TH)DP M. Mikirtytchiants (E2)

DI . G . Schug (LI)DI . I . Mohos (LI)

G . Schwiete (TH)Dr. H.P . Morsch (EI)

Dr. T . Sefzick (E1)Dr. R.-D . Neef (EI)

Dr. H. Seyfarth (E2)DP M. Nekipelov (E2)

Dr . A . Sibirtsev (TH)Prof. Dr . N.N . Nikolaev (TH) (since November 2, 2000)

DI K . Nünighoff (E1) Prof. Dr. K . Sistemich (E2)(apl . Prof. at the Univ. Köln)

Prof. Dr. W. Oelert (E1)(apl . Prof. at the Univ. Bochum) Prof. Dr . J . Speth (TH)

(Prof. at the Univ. Bonn)Dr. H . Ohm (E2)

DI . R. Stassen (LI)Dr. J . Oller (TH)

Dr. H.-J . Stein (E2)Dr. S . Papureanu (LI)(until Aug. 31, 2000) G. Sterzenbach (E1)

DI N. Paul (EI) Dr . H . Stockhorst (LI)

F . Pavlov (TH) Prof. Dr. H . Str6her (E2)(since September 4, 2000) (Prof. at the Univ. Köln)

DI Ch. Pohl (E1) Dr . R. T61le (LI)

Dr. D . Prasuhn (LI) DP M. Walzl (TH)

DP D. Protic (Dt) DP Z. Wang (TH)(until June 27, 2000)

Dr . F . Rathmann (E2)Dr. K.-H . Watzlawik (E2)

Dr. E. Roderburg (E 1)Dr . P . Wintz (E 1)since May 17, 2000

Dr. A. Wirzba (TH)M. Kremer (Ws)

DI M. Wohimuther (E1), Th . Krings (Dt)since Feb. 1, 2000 G . Krol (LI)

DI . K. Kruck (LI)Dr. M . Wolke (EI) M. Küven (Ws)

K. G. Langenberg (Li)Dr. E . Zaplatin (LI) W. Lorenz (Ad)(until Aug. 31, 2000) G . Urken (Ec)

H . Metz (Dt)Technical and Administrative Staff.

A. Müller (LI)DI A. Mussgiller (E2)

C . Berchem (Ec), R. Nellen (Ec)since Aug . 1, 2000 J . Pfeiffer (Dt),P . Birx (LI) until May 31, 2000R . Bley (Ad) DP. H . J. Probst (Rp)H. J . Böge (LI) H . Pütz (LI)M. Böhnke (LI) A . Retz (Cd),DI. N . Bongers (LI) until July 31, 2000DI W. Borgs (E2)

DI. A. Richert (LI)H. Borsch (LI)

U . Rindfleisch (Cd)

DI. R. Brings (LI)G . Roes (Ad)

P. Brittner (LI)N. Rotert (LI)

E . Brdkel (Ec),D. Ruhrlg (LI)

until Aug . 31, 2000T. Sageflca (L1)F. Schelba (LI)E . Buscholl (Cd), Jos . Schmitz (Ws),since Aug. 1, 2000 until Sept . 30, 2000J . But (Ws) Jü . Schmitz (LI)M. Comuth (Ad) F. Schultheiß (Ws)L . Conin (LI) DI . M . Simon (LI)B . Dahmen (LI) H. Singer (LI)

C . Deliege (LI) DI . K . Sobotta (LI)W. Derissen (Cd) D.W. Spölgen (Ws)N. Dolfus (Ec) J . Strehl (Ws)G. D'Orsaneo (E2) E. Tesch (Ad),R. Enge (LI) until Oct. 31, 2000J . Engel (LI) DI. T. Vashegyi (LI)P . Engels (LI) K.-P . Wieder (E2)(until Dec . 31, 2000) K . Winkler (Ec),B . Erkes (LI) until Sept. 30, 2000W.-R. Ermer (E2) DI . J.-D . Witt (LI)W. Ernst (Ec) M. Zander (LI)K. Esser (Ad) H. W. Zens (LI)DI . F . J . Etzkorn (LI)H . P . Faber (LI)G . Fiori (Dt) (E 1) Institute for Experimental Nuclear Physics 1H.-W. Firmenich (Ws) (E2) Institute for Experimental Nuclear Physics 2N. Gad (LI) (Th) Institute for Theoretical Nuclear PhysicsD. Gehsing (LI) (LI) Large Nuclear Physics InstrumentsS . Geisler (Cd) (Ad) AdministrationJ. GBbbels (Rp) (Cd) Construction and DesignH. Hadamek (Ws) (Da) Data Acquisition GroupA. Hamacher (Dt), (Dt) Detector and Target Laboratoryuntil Sept. 30, 2000 (Ec) ElectronicsR. Hecker (LI) (Rp) Radiation Protectionsince May 15, 2000 (Ws) Mechanical WorkshopM.G . Holona (Ws)K. D. Jach (LI)H.M . Jäger (E1)H.J. Jansen (Ws)R . Janssen (Ad)M. Karnadi (E2)R . Klein (E 1)K . Krafft (Rp)

Research Visitors(for one week to six months) :

Dr. V . Abaev (E2)from February 13 to April 16, 2000(St . Petersburg Nucl . Phys . Inst ., Gatchina, St . Petersburg)

Dr . V. Afonasiev (E2)from February 27 to April 9, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Prof. Dr. B . Ananthanarayan (Th)from May 13 to June 5, 2000(Indian Institute ofScience, Bangalore 560012India)

DP M. Abd El-Bary (EI)Research sholarship(NRC, AEA, Egypt)

Dr . V. Balanutsa (E2)from May 21 to June 18, 2000from September 8 to October 22, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Prof. T . Barnes (Th)(DFG-Fellow)until July 31, 2000(University ofTennessee, USA)

Dr. S . Barsov (E2)from January 23 to March 19, 2000from April 9 to May 31, 2000from September 4 to November 3, 2000from November 15 to December 24, 2000(St. Petersburg Nucl. Phys . Inst., Gatchina, St. Petersburg)

Dr. Thomas Becher (Th)from February 2 to February 11, 2000(University ofBern, Switzerland)

Dr . A . Beda (E2)from June 10 to June 16, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . V . Biryukov (LI)from Sept. 20 to Sept. 30, 2000)(JINP, Moskow, Russia)

V . Bollini (E1)from Nov . 13 to 17, 2000(Jagellonian Univ., Cracow, Poland)

A. Bubak (E 1)from May 1 to 11, 2000from Nov. 13 to 17, 2000(Univ . ofSilesia, Katowice, Poland)

DP J . Budzinski (El)from March 15 to April 15, 2000(Jagellonian Univ . of Krakow, Poland)

Dr . A . Bukharov (E2)from May 3rd to 315 `, 2000from June 12 to July 2nd, 2000from November 6 to December 3rd, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr. A. Chatterjee (EI)from June 19 to July 31, 2000(BARC Indien)

Dr. S . Cherman (E2)from November 26 to December 24, 2000(St . Petersburg Nucl. Phys . Inst ., Gatchina, St . Petersburg)

Dr. V . Chernetsky (E2)from March 26 to April 23, 2000from June 12 to July 2nd, 2000from Oktober to November 25, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Prof. V . Chernyshev (E2)from February 27 to April 16, 2000from May 3rd to 31 5`, 2000from June 12 to July 2nd, 2000from November 5 to December 10, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . B . Chiladze (E2)from April 12 to May 4, 2000from October 4 to 25, 2000(High Energy Phys . Inst ., Tbilisi State University, Tbilisi,Georgien)

Dr. M. Chumakov (E2)from April 23rd to June 11, 2000from September 8 to October 13, 2000from November 19 to December 3rd, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . M. Debowski (E2)from January 31rd to February 20, 2000(Forschungszentrum Rossendorf, Dresden)

Prof. S . Drozdz (Th)from March 16 to April 3, 2000from August 6 to August 12, 2000from October 3 to December l, 2000(University ofKrakow, Poland)

Prof. J.W. Durso (Th)from June 29 to November 11, 2000(Mount Holyoke College, Hadley, MA, USA)

Pavel Fedorets (E2)from May 8 to July 9, 2000from September 3 to July 2"d, 2001(Institute for Theoretical and Experimental Physics,Moskau)

Dr. D . Friesel (LI)from January 23 to January 30, 2000(IUCF, Bloomington, USA)Dr. A. Gerasimov (E2)from 14 March to 9 April, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Prof. Dr. 1 . Ginzburg (Th)from March 7 to April 6, 2000(S.L. Sobolev Institute, Novosibirsk, Russia)

Dr. L. Golovanov (E1)From Nov. 20 to Nov. 29, 2000(JINR Dubna, Russia)

Dr . E . Golubeva (E2)from November 5 to December 17, 2000(Institute for Theoretical and Experimental Physics,Moskau)

A. Gorski (Th)(DLR-Fellow)from March 16 to April 3, 2000(University of Krakow, Poland)

Dr . V . Goryachev (E2)from May 7 to June 18, 2000from September 24 to October 8, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . V . Grishina (E2)from January 23`d to March 19, 2000from October 29 to December 24, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr. L. Gusev (E2)from March 19 to April 30, 2000from June I 1 to July 2nd, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . C. Hanhart (Th)from April 28 to May 29, 2000(INT Seattle, USA)

H.E. HassanResearch sholarsphip(NRC, AEA, Egypt)

DP P . Hawranek (E1)Research sholarship(Univ . Krakau, Poland)

A. Heczko (E1)from Feb. 1 to 10, 2000from May 7 to 15, 2000(Jagellonian Univ . Cracow, Poland)

Prof. Dr . Pauchy W.-Y . Hwang (Th)(DAAD-fellow)from June 24 to July 29, 2000(National Taiwan University, Taipei)

Y . Ilieva (EI)from June 28 to Aug . 1, 2000from Sept . 19 to Oct . 17, 2000from Nov . 21 to Dec . 20, 2000(Inst. ofNucl . Res. and Nucl. Energy, Sofia, Bulgaria)

Prof. L . Jarczyk (E1 + E2)from January 16 to February 13, 2000from March 15 to May 15, 2000(Jagellonian University Cracow, Poland)

V . Jha (E1)from Nov . 10 to Dec. 16, 2000(BARC Indien)

Dr. B. Julia (Th)since September 18, 2000(University of Salamanca, Spain)

Prof. S. Kamerdzhiev (Th)from October 4 to December 3, 2000(IPPE, Obninsk, Russia)Russia)

Prof. B. Kamys (E1)from April 30 to May 11, 2000from August 27 to September 24, 2000(Jagellonian University Cracow, Poland)

Dr . A . Katcharava (E2)from January 31rd to February 21 Ist, 2000from April 12 to May 3rd, 2000(Joint Inst . for Nucl. Res ., Dubna, Moskau)

D. Kirillov (El)from June 29 to July 11, 2000from Sept . 13 to Oct. 10, 2000(JINR Dubna, RuBland)

Dr . Y. Kiselev (E2)from June 5' h to July 8"d, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Dr . J . Kisiel (El)from May i to 11, 2000(Univ. of Silesia, Katowice, Poland)

Dr. St. Kistryn (E1)from Dec . I 1 to Dec . 22, 2000(Univ . Krakau, Polen)

Dr. E . Kitanina (E2)from October 11 to November 1 5`, 2000(St . Petersburg Technical University)

Dr . St. Kliczewski (El)from June 11 to July 15, 2000from Sept . 10 to Dec. 17, 2000(Kernforschungszentrum Krakow, Poland)

W. Klimala (E1)from June 29 to July 18, 2000from Sept. 10 to Dec . 17, 2000(Jagellonian Univ. of Krakow, Poland)

Dr . D . Kolev (EI)from April 6 to 12, 2000(University of Sofia, Sofia, Bulgaria)

Prof. V. Komarov (E2)from April 12 to May 10, 2000from July 20 to August 11, 2000(Joint Inst . for Nucl . Res ., Dubna, Moskau)

Prof. Dr. L . Kondratyuk (Th + E2)from January 23rd to February 20, 2000from April 19 to May 13, 2000(Institute for Theoretical and Experimental Physics,Moskau)

Prof. V . Koptev (E2)from January 12 to March 11, 2000from April 10 to June 9, 2000from July 26 to August 6, 2000from September 6 to November 8, 2000(St . Petersburg Nucl . Phys . Inst., Gatchina, St . Petersburg)

Dr. A . Kovalev (E2)from May 17 to June 18, 2000from November 26 to December 24, 2000(St . Petersburg Nucl. Phys. Inst ., Gatchina, St . Petersburg)

DP P. Kowina (E1)Research sholarship(Univ . of Katowice, Poland)

Dr. V . Kozlov (E1)from Feb . 10 to April 8, 2000from Oct . 16 to Dec . 20, 2000(Moscow State Univ., Russia)

Dr . M . Kravcikovafrom Sept. 21 to Oct . 1, 2000(Technische Universität Kosice, Slovakia)

Dr. P . Kravtsov (E2)from January 9 to March 8, 2000from September 3 to November 1St, 2000(St. Petersburg Nucl . Phys . Inst ., Gatchina, St . Petersburg)

Prof. Dr. G . Krein (Th)from November 30 to December 23, 2000(UNESP Sao Paulo, Brasil)

Prof. Dr. A . Kudryavtsev (Th)from March 20 to April 19, 2000from November 27 to December 23, 2000(ITEP Moscow, Russia)

Dr . A . Kulikov (E2)from January 31 St to February 21 St, 2000from March 9 to 23rd , 2000from April 12 to May 1St , 2000from September 7 to 20, 2000(Joint Inst. for Nucl . Res., Dubna, Moskau)

Dr. V. Kurbatov (E2)from February 1St to 22, 2000from April 11 to May 2nd, 2000from October 23rd to December 3rd, 2000(Joint Inst . forNucl . Res., Dubna, Moskau)

Prof T. Kutsarova (E 1)from June 27 to July 10, 2000from Sept. 19 to Oct. 14, 2000(Acad. Science, Sofia, Bulgaria)

Dr . V . Leontiev (E2)from September 4 to 18, 2000(Joint Inst. for Nucl. Res., Dubna, Moskau)

Prof. J. Lieb (E 1)from March 21 to May 17, 2000from Nov. 20 to 28, 2000(George Mason University, VA, USA)

Dr. L.N . Lipatov (Th)from August 27 to August 31, 2000(NPI St . Petersburg, Gatchina, Russia)

Dr. G. Macharashvili (E2)from January 31 st to February 21 st, 2000from April 12 to May 3rd, 2000from July 20 to August 11, 2000from November 6 to 27, 2000(Joint Inst . for Nucl. Res., Dubna, Moskau)

Dr . A . Magiera (E1)until Dec . 31, 2000(Kemforschungszentnun Krakau, Poland)

J . Majewski (El)from March 15 to April 10, 2000from May 13 to June 13, 2000from July 15 to August 16, 2000from Oct. 21 to Dec . 20, 2000(Jagellonian Univ . ofKrakow, Poland)

Prof. Dr. S . Manayenkov (Th)from January 23 to February 20, 2000from October 4 to October 29, 2000(NPI St. Petersburg, Gatchina, Russia)

Prof. G . Martinska (E1)from July 3 to 18, 2000from Sept . 21 to Oct . 8, 2000(Univ . ofKosice, Slowakia)

Dr. S . Merzliakov (E2)from February 1St to May 1St, 2000from July 2nd to August 13, 2000from September 3rd to October 15th , 2000from October 29 to December 20th , 2000(Joint Inst. for Nucl. Res., Dubna, Moskau)

W. Migdal (E1)from Dec . 6 to Dec . 22, 2000(Jagellonian Univ . ofKrakow, Poland)

Dr. S . Mikirtytchiants (E2) Dr. O . Petrus (E2)from January 17 to March 16, 2000 from January 24 to March 23rd, 2000from September 10 to November 1 5`, 2000 from April 17 to May 8, 2000(St. Petersburg Nucl . Phys. Inst ., Gatchina, St . Petersburg) from August 28 to September 24, 2000

from November 27 to December 22nd, 2000A. Misiak (EI) (Joint Inst. for Nucl . Res., Dubna, Moskau)from March 20 to April 15, 2000from Oct. 29 to Nov. 30, 2000 N. Piskunov (E1)(Jagellonian Univ. ofKrakow, Poland) from April 6 to 15, 2000

from June 29 to July 11, 2000Dr. P . Moskal (E 1) from Sept . 30 to Oct . 10, 2000from March 15 to April 14, 2000 (JINR Dubna, RuBland)since July 1, 2000(Jagellonian Univ. of Krakow, Poland) Dr. S. Podchasky (E2)

from April 23rd to June 4 2000Prof. Dr. H . Nann (E1) from June 18 `" to July 2nd, 2000from June 30 to July 14, 2000 from November 5 to December 3rd, 2000

(IUCF Bloomington, USA) (Institute for Theoretical and Experimental Physics,Moskau)

Prof. Dr . K. Nakayama (Th) E. Podsvirova (El)from May 11 to August 7, 2000 from Oct. 4 to Nov. 3, 2000(University ofGeorgia, Athens, USA) (loffe Institute St . Petersburg, Russia)

Dr . V . Nelyubin (E2) Dr . K. Pysz (E1 + E2)from August 20 to September 20, 2000 from Feb . 15` to 10, 2000(St. Petersburg Nucl . Phys . Inst ., Gatchina, St. Petersburg)from March 8 to April 5, 2000

Prof M. Nioradze (E2) from July 315` to September 17`s , 200022nd, 2000

from April 12 to May 3rd , 2000 from December 7 to(Jagellonian University Cracow, Poland)

from October 4 to 25, 2000(High Energy Phys . Inst., Tbilisi State University, Tbilisi,

M. Rossewij (El)Georgien) Research sholarship

Dr . S . Orfanitski (El) until Oct . 14, 2000(Utrecht Univ., The Netherlands)

from Feb . 10 to April 8, 2000from Oct. 16 to Dec . 20, 2000

Dr. B. Roy (E1)(Moscow State Univ., Russia) from June 19 to July 31, 2000

from Nov. 10 to Dec . 16, 2000Dr. P . Page (Th) (BARC Indien)from July 10 to July 15, 2000(LANL, Los Alamos, USA) Dr . Z. Rudy (E2)

from August 27 to September 24, 2000Dr . E . Paryev (E2) (Jagellonian University Cracow, Poland)from June 5 to July 8nd, 2000(INR Russian Academy of Siences, Moskau) Prof. T. Rzaca-Urban

from June 30 to July 28, 2000F . Pavlov (Th) (Univ. of Warsaw, Poland)from January 23 to February 20, 2000(NPI St . Petersburg, Gatchina, Russia) M. Sawa (Th)

from March 16 to April 3, 2000A. Pasternak (El) (Marie Curie-Sklodowska University Lublin,from Sept . 4 to Nov. 3, 2000 Poland)(Ioffe Institute St . Petersburg, Russia)

Prof. E. Schachinger (El)Prof. Dr. T . Pena (Th) from May 21 to 25, 2000from May 15 to May 21, 2000 (TU Graz, Austria)(Technical University ofLissabon, Portugal)

Ch . Schneider (E2)Dr . L . Pentchev (El) from January 31 5 ` to February 19, 2000from June 28 to July 11, 2000 (Forschungszentrum Rossendorf, Dresden)

(INRE, Sofia, Bulgaria)Dr. A . Sibirtsev (Th)from August 7 to August 11, 2000(University ofGiessen)

Dr . M. Siemasczko (E I )from March 25 to April 8, 2000from June 18 to 25, 2000from July 10 to 21, 2000from Nov. 5 to Dec . 17,2000(University of Katowice)

D. Sitnik (E1)from April 6 to 15, 2000from June 29 to July 11, 2000from Sept. 30 to Oct. 10, 2000from Nov. 20 to Nov. 29, 2000(JINR Dubna, RuBland)

Dr. R. Siudak (E1)from June 11 to July 15, 2000from Sept. 10 to Dec . 17, 2000(Jagellonian Univ . of Krakow, Poland)

I . Slepnev (E1)from Sept. 13 to Oct . 3, 2000(JINR Dubna, RuBland)

Dr. J . Smyrski (E1)from March 20 to April 9, 2000(Jagellonian University, Krakau, Polen)

J . Sobczyk (E1)from March 20 to April 2, 2000(Jagellonian University, Krakau, Polen)

Dr . E . Swanson (Th)from July 12 to July 19, 2000(University ofPittsburgh and Jefferson Lab., USA)

Dr. A. Szczurek (Th)(DLR-fellow)from March 16 to April 17, 2000from October 4 to November 24, 2000(University ofKrakow, Poland)

Dr. G. Tertychny (Th)from September 28 to November 24, 2000(IPPE, Obninsk, Russia)

Frau DI A. Tietze (E1)from Jan . 1 to Oct. 31, 2000(Berg. Univ. Gesamthochschule Wuppertal)

V. Uleshenko (Th)(DLR-fellow)from March 16 to April 17, 2000(University ofKrakow, Poland)

DP M. Ulicny (E1)Research sholarship(Univ . ofKosice, Slowakia)

Dr . J . Urban (El)from May 29 until Feb. 28, 2001(Univ . of Kosice, Slowakia)

Dr . W. Urban (EI)from June 30 to July 28, 2001(Univ . of Warsaw, Poland)

Dr . Y . Uzikov (E2)from February 3rd to 24, 2000from April 6 to May 6, 2000from October 15 to December 4, 2000(Joint Inst. for Nucl . Res., Dubna, Moskau)

Dr . A . Vassiliev (E2)from January 17 to March 16, 2000from May 24 to June 28, 2000from October 1St to 14, 2000from November 19 to December 24, 2000(St. Petersburg Nucl . Phys . Inst., Gatchina, St. Petersburg)

Dr . Y . Venkova (EI)from Jan. 3 to 12, 2000(Bulg . Akademie der Wiss., Sofia, Bulgarien)

Dr. A. Volkov (E2)from March 9 to 23rd, 2000from April 19 to May 17, 2000(Joint Inst. for Nucl . Res ., Dubna, Moskau)

Prof. C . Wilkin (E2)from March 4 to 1], 2000(Univ . College London, GB)

Dr. A . Wirzba (Th)since January 1, 2000(SUNY at Stony Brook, USA)

A. Wronska (EI )from Sept. 10 to Oct. 14, 2000(Jagellonian Univ . ofKrakow, Poland)

Dr . S . Yaschenko (E2)from April 12 to May 3rd , 2000(Joint Inst . for Nucl . Res ., Dubna, Moskau)

Dr. B.G . Zakharov (Th)(DFG-fellow)from August 1 to August 31, 2000from November 2 to December 23, 2000(Landau Inst. for Theor. Phys., Moscow, Russia)

Dr . B . Zalikhanov (E2)from January 26 to May 1 St, 2000from August 28 to November 27, 2000(Joint Inst. for Nucl . Res., Dubna, Moskau)

Dr. V . Zoller (Th)(DFG fellow)from October 2 to December 23, 2000(ITEP, Moscow, Russia)

P . Zupranski (EI)from June 19 to July 1, 2000from Oct . 17 to Nov. 1, 2000(Soltan Institute for Nuclear Studies, Warschau, Poland)

Dr. l . Zychor (E2)from January 31 to March 30, 2000from May 29 to July 21 St , 2000(Soltan Inst . for Nucl . Studies, Swierk-Otwock, Poland)

X. PUBLICATIONS

Journals

IKP-00-11-001Barsov, S.,Bechstedt, U.,Borchert, G., Borgs, W., BOscher, M .,Debowski, M .,Drochner, M.,Erven,W,

Eger, R.,Fedorets,P,Gotta, D., Hartmann, M ., Junghans, H ., Kacharava, A ., Kamys, B .,Klehr, F.,

Koch, H . R.,

Komarov, V I .,

Koptev, !/,Kulesssa,P,Kulikov, A.,Kurbatov, V.,Macharashvili, G:,

Maier, R .,Mikirtichyants, S .,Merzliakov, S.,

Müller, H.,

Mussgiller, A .,Nioradze, M.,

Ohm, H.,

Petrus, A .,

Prasuhn, D.,Pysz,K.,Rathmann, F.,Rimarzig, B.,Rudy,Z.,Schleichert, R.,Schneider, Chr.,

Schneider, H .,Schult,0. W. B.,

Seyfarth, H .,Sistemich, K., Stein, H . J . and Str6her, H ., WOstner, P for the ANKEcollaborationFirst results from subthreshold K'-production measurements withANKENucl . Phys. A675 (2000) 230c20.45 .0

IKP-00-11-002Barsov, S.,Bechstedt, U.,Borchert,G.,Borgs,W.,B0scher,M.,Debowski, M.,Erven,W.,

Esser, R.,

Fedorets, P,

Gotta, D.,Hartmann, M ., Junghans, H ., Kacharava, A ., Kamys, B ., Klehr, F,Koch, H . R.,

Komarov, V I.,

Koptev, V.,Kulessa,P,

Kulikov, A.,Kurbatov, V,

Macharashvili, G.,

Maier, R .,

Merzliakov, S.,Mikirtytchiants, S .,

Mailer, H .,

Mussgiller, A.,Nekipelov,M.,Nioradze, M.,

Ohm, H.,

Petrus, A.,

Prasuhn, D .,Pysz,K.,Rathmann, F

Rimarzig, B .,Rudy,Z.,Schleichert,R.,Schneider, Ch .,

Schneider, H .,Schult,0.W. B .,

Seyfarth, H .,Sistemich, K ., Stein, H . J ., Str6her, H . and Zychor, I.Measurementof Subthreshold K' Production in pA Collisions with ANKEActa Phys. Pol. B, Vol . 31, 10 -11 (2000) 215920.45 .0

IKP-00-11-003Barnes TExotic Mesons, Theory and ExperimentProc. of the Workshop "MESON2000", Krakow, Poland, 18.-23.5.2000, Acta Phys . Pol. Vol . 31 (2000) 2545-255620.80 .0

IKP-00-11-004Baru V., Kudryavtsev A ., Tarasov V.,Briscoe W., Dhuga K ., Strakovsky I.Charge Symmetry Violation Effects in Pion Scattering off LightNucleiPhys . Rev. C62 (2000) 044003320.80 .0

IKP-00-11-005Baru V, Gasparian A.M ., Haidenbauer J., Kudryavtsev A.E., SpethJ .FSI Effects in Meson Production in NN CollisionsProc. ofthe Conference "MESON 2000", Krakow, Poland, 18 .-23.5.2000Acta Phys . Pol . B, Vol. 31 (2000) 2127-213120.80.0

IKP-00-11-006Baur G .Influence of Damping on the Excitation ofthe Double GiantResonanceEur. Phys . J A7 (2000) 55-5820.80.0

IKP-00-11-007Benhar 0 ., Nikolaev N.N ., Speth J ., Usmani A.A:, Zakharov B.G .

Final State Interactions in HE(e,e p) H at Large Proton EnergyNucl . Phys . A673 (2000) 24120.80.0

IKP-00-11-008Betigeri M ., Bojowald J ., Budzanowski A., Chatterjee A., Drochner

M., Ernst J ., F6rtsch S ., Freindl L ., Frekers D., Garske W., GrewerK., Hamacher A., Igel S., Ilieva J ., Jahn R., Jarczyk L ., KemmerlingG ., Kilian K ., Kliczewski S., Klimala W., Kolev D ., Kutsarova T, Lieb

J ., Lippert G ., Machner H., Magiera A ., Nann H ., Pentchev L .,

Plendl H.S ., Protic D ., Razen B ., von Rossen P., Roy B.R ., Siudak

R ., Smyrski J ., Strzalkowski A.A ., Tsenov R., Zolnierczuk PA .,Zwoll K.

227

Measurement of p+d-> 3 He+,j in the S 11 ResonancePhys . Left . B427 (2000) 26720.45 .0

IKP-00-11-009Betigeri M., Bojowald J ., Budzanowski A., Chatterjee A., DrochnerM., Ernst J ., F6rtsch S ., Freindl L., Frekers D., Garske W., GrewerK., Hamacher A ., Igel S ., Ilieva J., Jahn R ., Jarczyk L ., KemmerlingG ., Kilian K ., Kliczewski S., Klimala W., Kolev D., Kutsarova T, LiebJ ., Lippert G ., Machner H., Magiera A., Nann H., Pentchev L.,Plendl H.S ., Protic D., Razen B ., von Rossen P, Roy B.R., SiudakR ., Smyrski J., Strzalkowski A.A ., Tsenov R ., Zolnierczuk PA.,Zwoll K .Test of Charge Independence in p+d->(A=3)+Pion ReactionsProc. of the "PANIC99" Conference, Uppsala, SwedenNucl. Phys. A663 & A664 (2000) 963c20.45.0

IKP-00-11-010Bernard V., Krebs H ., Meißner Ulf-G.Neutral Pion Electroproduction off DeuteriumPhys. Rev. C61 (2000) 05820120.80.0

IKP-00-11-011Bernard V., Kaiser N ., Meißner Ulf-G .The Pion Charge Radius from Charged Pion ElectroproductionPhys . Rev. C62 (2000) 02820120.80 .0

IKP-00-11-012Bilger R ., Blom M ., Bogoslawsky D ., Bondar A ., Brodowski W.,Brodowski W., Calen H ., Chuvilo I., Clement H ., Dunin V., Dyring J .,Ekstr6m C ., Fransson K., Friden C.-J., Gustafsson L., Häggstr6mS ., Hüistad B ., Jacewicz M., Johanson J ., Johansson A ., JohanssonT, Khoukaz A ., Kilian K. Kimura N ., Koch I ., Kolachev G .,Komogorov M., Kullander S., Kupsc A ., Kurdadze L. Kuzmin A .,Kuznetsov A ., Marciniewski P, Martemyanov A., Martemyanov B .,Morosov B ., M6rtsell A ., Nawrot A ., Oelert W., Oreshkin S .,Petrukhov Y, Povtorejko A ., Przestrzelska K., Pätzold J ., ReistadD ., Ruber R.J.M .Y, Sandukovsky V., Schuberth U . Sefzick T.Sidorov V, Shwartz B . Sopov V, Stepaniak J. Sukhanov A .,Sundberg P, Tchernychev V., Tikhomirov V, Turowiecki A,, WagnerG., Wilhelmi Z ., Yamamoto A ., Yamaoka H ., Zabierowski J., ZernovA. Zlomanczuk J .The CELSIUSIWASA FacilityActa Phys . Pol. B, Vol . 31 (2000) 7720.50 .0

IKP-00-11-013Bilger R., Blom M., Bogoslawsky D ., Bondar A ., Brodowski W.,Calen H ., Chuvilo I ., Clement H ., Dunin V., Dyring J ., Ekstrdm C .,Fransson K ., Friden C .-J ., Gustafsson L ., H5ggstr6m S ., Höistad B.,

Jacewicz M ., Johanson J ., Johansson A ., Johansson T., KhoukazA., Kilian K . Kimura N ., Koch I ., Kolachev G ., Komogorov M.,Kullander S ., Kupsc A., Kurdadze L. Kuzmin A ., Kuznetsov A .,Marciniewski P, Martemyanov A ., Martemyanov B., Morosov B .,Mürtsell A ., Nawrot A ., Oelert W., Oreshkin S ., Petrukhov Y,

Povtorejko A., Przestrzelska K ., Pätzold J., Reistad D ., Ruber

R.J.M .Y, Sandukovsky V, Schuberth U . Sefzick T Sidorov V,

Shwartz B. Sopov V, Stepaniak J . Sukhanov A ., Sundberg P,

Tchernychev V., Tikhomirov V., Turowiecki A., Wagner G., Wilhelmi

Z., Yamamoto A., Yamaoka H ., Zabierowski J ., Zernov A .

Zlomanczuk J .The WASA Detector at CELSIUSProceedings of the 15th International Conference on Particles and

Nuclei, PANIC'99, Uppsala, Sweden, 10.-16 .6.1999

Nucl . Phys . A, Vol . 663-664 (1-4) (2000) pp . 1073-107620.50 .0

IKP-00-11-014Bräutigam, W. ; Felden, 0 . ; Maier, R . ; Martin, S . ; Schnase, A. ;

Schug, G . ; Stassen, R. ; Zaplatin, E .Design considerations for the linac system of the ESS

Nuclear Instruments & Methods in Physics Research

B 161-163 (2000) 1148-115320.91 .0

IKP-00-11-015BOttiker P., Meißner Ulf-G .Pion-Nucleon-Scattering inside the Mandelstarr TriangleNucl . Phys. A668 (2000) 9720.80 .0

IKP-00-11-016Cloth, P ; Filges, D . and the members of the ZEUS Collaboration :Measurement of Inclusive Prompt Photon Photoproduction at HERAPhys.Lett.B472 (2000) 175-18820.48 .0

IKP-00-11-017Cloth, P ; Filges, D . and the members ofthe ZEUS Collaboration :

Measurement of the

ET .let/ Q2

Dependence of Forward-Jet

Production at HERAPhys.Lett.B474 (2000) 223-23320.48 .0

IKP-00-11-018Cloth, P ; Filges, D . and the members of the ZEUS Collaboration :The Q2 Dependence of Dijet Cross Sections in yp Interactions atHERAPhys.Lett.B479 (2000) 37-5220.48 .0

IKP-00-11-019Cloth, P. ; Filges, D . and the members of the ZEUS Collaboration :Measurement of Azimuthal Asymmetries in Deep InelasticScatteringPhys.Lett.B481 (2000) 199-21220.48 .0

IKP-00-11-020Cloth, P ; Filges, D . and the members of the ZEUS Collaboration :Measurement of Inclusive D+y Photoproduction at HERAPhys.Lett.B481 (2000) 213-22720.48 .0

IKP-00-11-021Cloth, P. ; Filges, D . and the members ofthe ZEUS Collaboration :Measurement of the Proton Structure Function F2 at Very Low Q2 atHERAPhys.Lett.B487 (2000) 53-7320.48 .0

IKP-00-11-022Cloth, P ; Filges, D . and the members of the ZEUS Collaboration :Measurement ofexclusive w electroproduction at HERAPhys.Lett.B487 (2000) 273-28820.48 .0

IKP-00-11-023Cloth, P. ; Filges, D . and the members ofthe ZEUS Collaboration :Angular and Current-Target Correlations in Deep InelasticScattering at HERAEucPhys. J . C12 (2000) 53-6820.48.0

IKP-00-11-024Cloth, P; Filges, D . and the members ofthe ZEUS Collaboration :Measurement of D* Production and the Charm Contribution to F2 inDeep Inelastic Scattering at HERAEur.Phys . J . C12 (2000) 35-5220.48 .0

IKP-00-11-025Cloth, P ; Filges, D. and the members of the ZEUS Collaboration :Measurement of the Spin-Density Matrix Elements in ExclusiveElectroproduction of p° Mesons at HERAEucPhys . J . C12 (2000) 393-41020.48.0

IKP-00-11-026Cloth, P. ; Filges, D . and the members ofthe ZEUS Collaboration:Measurement of Diffractive Photoproduction of Vector Mesons atLarge Momentum Transfer at HERAEucPhys . J . C14 (2000) 213-23820.48 .0

IKP-00-11-027Drozdz S ., GrOmmer F., Gorski A ., Ruf F., Speth J .,Dynamics of Competition between Collectivity and Noise in theStock MarketPhysica A287 (2000) 44020.80 .0

IKP-00-11-028Egidy, v.T ; Figuera, P. ; Galin, J . ; Goldenbaum, F. ; Golubeva, Ye.S . ;Hasinoff, M. ; Hilscher, D. ; Iljinov, A.S. ; Jahnke, U . ; Krause, M . ;Kurcewicz, Ledoux, X . ; Lott, B . ; Maier, L. ; Manrlque de Lara, M . ;Pausch, G . ; Pienkowski, L . ; Quednau, B . ; Rossner, H . ; Schott, W. ;Schrader, WU. ; Toke, J . :Neutrons produced by 1.22 GeV antitproton interactions with nucleiEur. Phys . A 8 (2000) 19720.48.0

IKP-00-11-029Elster Ch ., Fachruddin I ., G16ckle W.Nucleon-nucleon Scattering in a Three Dimensional ApproachPhys. Rev. C62 (2000) 044002-120.80.0

IKP-00-11-030Epelbaum E ., Glückle W., Meißner Ulf-G .Nuclear Forces from Chiral Lagrangians using the Method ofUnitary Transformation (11) : The Two-nucleon SystemNucl . Phys. A671 (2000) 29520.80.0

IKP-00-11-031Fearing H.W., Hemmert T.R ., Lewis R., Unkmeir C .Radiative Pion Capture by a NucleonPhys. Rev. C62 (2000) 05400620.80 .

IKP-00-11-032Fettes N ., Meißner Ulf-G ., Steininger S ., Mojzis M .The Chiral Effective Pion-Nucleon Lagrangian of order p°Annals of Physics (NY) 283 (2000) 27320.80 .0

IKP-00-11-033Fettes N ., Meißner Ulf-G .Pion-Nucleon Scattering in Chiral Perturbation Theory II : FourthOrder CalculationNucl. Phys . A676 (2000) 31120.80 .0

IKP-00-11-034Fettes N., Meißner Ulf-G .Pion-nucleon Scattering in an Effective Chiral Field Theory withExplicit Spin-3/2 FieldsNucl . Phys . A679 (2000) 39920.80.0

IKP-00-11-035Fettes N ., Bernard V, Meißner Ulf-G.One-loop Analysis of the Reaction nN->n7cNNucl . Phys. A671 (2000) 26920.80 .0

IKP-00-11-036Filges, D ; Neef, R.D . ; Schaal, H . :Nuclear Simulation and Radiation Physics Investigations of theTarget Station of the European Spallation Neutron Source (ESS)Nuclear Technology, American Nuclear Society, Vol 132, Nr. 1(2000) 30-4820.90 .0

IKP-00-11-037Filges, D . ; Schaal, H . ; Broome, T. :Radiation Shielding and Protection of the European SpallationNeutron Source (ESS)Journal of Nuclear Science and Technology, Supplement 1 (2000)30-3420.90 .0

IKP-00-11-038Gasparian A., Haidenbauer J., Hanhart C .,Kondratyuk A.L ., Speth J .The Reactions pp->pAK` and pp->pZo K+ near their ThresholdsPhys. Left . B480, 273-279 (2000)20.80 .0

IKP-00-11-039Gellas G.C ., Hemmert T.R ., Meißner Ulf-G .Complete One-Loop Analysis of the Nucleon Spin PolarizabilitiesPhys . Rev. Left . 85 (2000) 1420.80.0

IKP-00-11-040Gilg H ., Gillitzer A ., Knülle M., MOnchW., Schott W., Kienle P,Itahashi K., Oyama K ., Hayano R.S ., Geissel H., Iwasa N .,Münzenberg G., Yamzaki 7:Deeply Bound Ti States in 207Pb Formed in the 208Pb(d, 3He)Reaction . I . Experimental Methods and ResultsPhys . Rev. C62 (2000) 025201-1 - 025201-1120.45 .0

IKP-00-11-041Gillitzer A . for the GSI-S160 CollaborationObservation ofwell-resolved 1s and 2p Ti States in Pb by highResolution (d,3He) SpectroscopyProceedings of the 15th International Conference on Particles andNuclei, PANIC'99, Uppsala, Sweden, 10.-16 .6.1999Nucl . Phys . A663&664 (2000) 206c-209c20.45.0

IKP-00-11-042GillitzerA .Deeply Bound Pionic States in PbProc. of the Workshop "MESON 2000", Krakow, Poland, 19.-23.5.2000Acta Phys. Pol . B31 (2000) 2581-258620.45 .0

IKP-00-11-043Golubeva, Ye . S .,

Cassing, W.,

Kondratyuk, L. A .,

Sibirtsev, A.,Büscher, M .Studying the coN Elastic and Inelastic Cross Section with NucleonsEur. Phys . J . A 7 (2000) 27120.45 .0

IKP-00-11-044Grishina, V. Yu, Kondratyuk, L. A., Büscher, M.co- and ~-Meson Production in pn->dM Reactions near Thresholdand OZI-Rule ViolationYad . Phys. 63,10 (2000) 191320.45 .0

IKP-00-11-045Grishina, V. Yu ., Kondratyuk, L. . A ., Bratkovskaya, E. L .,Büscher, M., Cassing, W.

Production of ao-mesons in the reactions nN->aoN and pp->da 00 at

GeV energiesEur. Phys . J . A 9 (2000) 27720.45.0

IKP-00-11-046Grishina V.Yu ., Kondratyuk L.A ., Büscher M ., Haidenbauer J.,

Hanhart C . Speth J .ij- and il'-meson Production in the Reaction pn->dM near Threshold

Phys . Left. B 475, 9-16 (2000)

IKP -00-11-047Grzonka, D ., Kilian, K .Experiments at COSYNucl . Phys . A670 (2000) 241c-248c20.45 .0

IKP-00-11-048Haidenbauer J ., Melnitchouk W., Speth J .Meson-exchange model forthe YN InteractionProc. ofthe "PANIC 99" Conf., Uppsala, Sweden, June 1999

Nucl . Phys . A633&644, 549c-552c (2000)20.80 .0

IKP-00-11-049Haidenbauer J ., SchäferW., Speth J .Pions in Hadron PhysicsProc. ofthe "MESON 2000" Conference, Krakow, Poland, 18.-23.5.2000Acta Phys . Pol . B31, 2321-2332 (2000)20.80 .0

IKP-00-11-050Hanhart C .NN->NNn from the Effective Field Theory Point ofView: ShortComings and GainsProc . of the Workshop "MESON2000", Krakow, Poland, 18.-23.5.2000, Acta Phys . Pol . Vol. 31 (2000) 2213-221720.80 .0

IKP-00-11-051Hanhart C., Haidenbauer J ., Krehl 0 ., Speth J .Polarization Phenomena in a Dynamical Model of NN->NNnProc. of the "PANIC 99" Conference, Uppsala, Sweden, June 1999Nucl . Phys . A633&644, 461c-464c (2000)20.80.0

IKP-00-11-052Hanhart C ., Haidenbauer J ., Krehl 0 ., Speth J .Polarization Phenomena in a Dynamical Model of NN->NNn nearThresholdPhys . Rev. C61 (2000) 06400820.80 .0

IKP-00-11-053Heim TA ., Hencken K., Trautmann D. Baur G .Coherent and Incoherent Atomic Scattering : Formalism andApplication to Pionium Interaction with MatterJ . Phys. B33 (2000) 3583-360420.80 .0

IKP-00-11-054Hemmert TR., Holstein B.R., Knochlein G ., Drechsel D .Generalized Polarizabilities ofthe Nucleon in Chiral EffectiveTheoriesPhys. Rev. D62 (2000) 01401320.80.0

IKP-00-11-055Hencken K ., Trautmann D ., Baur G .Production of Low Mass Electron Pairs Due to the Photon-PhotonMechanism in Central CollisionsPhys. Rev. C61 (2000) 027901XX20.80 .0

IKP-00-11-056Itahashi K., Oyama K., Hayano R.S ., Gilg H ., Gillitzer A ., Knülle M .,MOnch W., Schott W., Kienle P., Geissel H ., Iwasa N ., MünzenbergN ., Münzenberg G ., Hirenzaki S ., Toki H., Yamzaki T

Deeply Bound 7i States in 207Pb Formed in the Zo3 Pb(d3He)Reaction . II . Deduced Binding Energies and Widths and the Pion-NucleusPhys . Rev. C62 (2000) 025202-1 - 025202-1220.45 .0

IKP-00-11-057Jamin M ., OllerJ.A., Pich A.S-wave Kn Scattering in Chiral Perturbation Theory withResonancesNucl . Phys . B587 (2000) 33120.80 .0

IKP-00-11-058Jarczyk L., Guaraldo C ., Machner H. Magiera A.

Conference Proceedings of the Workshop "Meson2000", Krakow,

Poland, 19:23.5.2000Acta Phys . Pol . B31 (10-11) (2000) p . 2123-2794

20.45.0

IKP-00-11-059Kamerdzhiev S ., Speth J ., Tertychny G .Microscopic analysis of the breathing mode in °0Ca and 5 8Ni

Eur. Phys . J . A7,483-490 (2000)20.80 .0

IKP-00-11-060 IKP-00-11-068Khoukaz A., Adam H.H., Balewski J.T, Budzanowski A ., Goodman Lorentz, B., Häberli, W., Rathrnann, F, Wise, T, Doskow, J .,C ., Grzonka D ., Jarczyk L ., Jochmann M., Kilian K ., Lang N., Lister Dzemidzic, M ., Hardie, J . G ., Meyer, H . O ., Pollock, R . E ., vonT, Moskal P , OelertW., Quentmeier C., Santo R., Schepers G ., Przewoski, B ., Rinckel, T, Sperisen, F, and Pancella, P V.Seddik U ., Sefzick T, Sewerin S ., Smyrski J., Strzalkowski A., Angular distribution ofthe longitudinal pp a dpi+Wolke M., Wüstner F, Wyrwa D . .Near Threshold Production of rl, -q' and Charged Kaon Pairs in Phys. Rev. C 61 (2000) 064604Proton-Proton Collisions 20.45.0Proceedings of the 15th International Conference on Particles andNuclei, PANIC'99, Uppsala, Sweden, 10.-16 .6.1999 IKP-00-11-069Nucl . Phys. A, Vol . 663-664 (1-4) (2000) pp . 565-568 Magiera A., Machner H.20.50 .0 Charge and Isospin Symmetry breaking via External n -ij Mixing

Nucl. Phys . A674 (2000) 515IKP-00-11-061 20.45.0Kleber, V, Achenbach, P, Ahrens, J ., Beck, R ., Hejny, V, Kellie,J . D ., Kotulla, M., Krusche, B ., Kuhr, V., Leukel, R., Metag, V, IKP-00-11-070Novotny, R., Olrnos de Le6n, V., Owens, R. O ., Rambo, F, Matulewicz, T, Aphecetche, L., Charbonnier, Y, Delagrange, H .,Schmidt, A., Schumacher, M., Siodlaczek, U ., Str6her, H ., WeiB, J., Gudima, K. K., Martinez, G., Ploszajczak, M., Schutz, Y,Wissmann, F., Wolf, M. Toneev, V D., Appenheimer, M., Averbeck, R., Diaz, J .,Double-7r° photoproduction from the deuteron D6ppenschmidt, A ., van Goethem, M . J., Hlavac, S., Hoefman, M .,Eur. Phys . J . A 9, 1 (2000) 1 Holzmann, R ., Lefevre, F., Kugler, A., LBhner, H., Marfn, A .,20.50 .0 Metag, V., Novotny, R., Ostendorf, R . W., Siemssen, R . H .,

Simon, R. S ., Stratmann, R ., Strbher, H ., Tlusty, P, Vogt, P H .,IKP-00-11-062 Wagner, V., Weiss, J ., Wilschut, H . W, Wissmann, F, Wolf, A . R .,Klimala W., Betiged M ., Bojowald J ., Budzanowski A., Chatterjee A., Wolf, M .Ernst J ., Freindl L., Frekers D ., Garske W., Grewer K ., Hamacher Observation of At-4p7° decay in heavy-ion collisionsA., Ilieva J ., Jarczyk L ., Kemmerling G., Kilian K., Kliczewski S ., Eur. Phys. J . A 9, 69 - 72 (2000)Kolev D., Kutsarova T, Lieb J ., Machner H ., Magiera A., Nann H., 20.45 .0Pentchev L., Plendl H.S ., Protic D ., Razen B., von Rossen P, RoyB.R., Siudak R., Srnyrski J ., Srikantiah RY, Strzalkowski A.A., IKP-00-11-071Tsenov R., Zolnierczuk PA., Zwoll K. Meißner Ulf-G., Rakhlmov A., YakhshievMeson Production in p+d Reactions The Nucleon-Nucleon Interaction and Properties of the Nucleon in aActa Phys . Pol . 32 (2000) 2231 npw Soliton Model including a Dilaton Field20.45.0 Phys . Left . B473 (2000) 200

20.80 .0IKP-00-11-063Krehl O ., Hanhart C ., Krewald S ., Speth J . IKP-00-11-072What is the structure of the Roper Resonance? Meißner Ulf-G., Oller J.A.Phys. Rev. C62 (2000) 25207 Chiral Unitary Meson-Baryon Dynamics in the Presence of20.80 .0 Resonances: Elastic Pion=Nucleon Scattering

Nucl . Phys. A673 (2000) 311IKP-00-11-064 20.80 .0Kubis B., Meißner Ulf-G.Virtual Photons in the Pion Form Factors and the Energy- IKP-00-11-073momentum Tensor Meißner Ulf-G., Oller J .A .Nucl . Phys. 671 (2000) 33120.80.0

J /T --> Omr(KK) Decays, Chiral Dynamics and OZI ViolationNucl . Phys. A679 (2000) 372

IKP-00-11-065 20.80 .0Letoumeau, A. ; Galin, J. ; Goldenbaum, F ; Loft, B . ; Pdghaire, A . ; IKP-00-11-074Enke, M . ; Hilscher, D . ; Jahnke, U . ; Nünighoff, K . ; Filges, D. ; Neef, Meißner Ulf-G .R.D . ; Paul, N . ; Schaal, H . ; Sterzenbach, A. :Neutron

G . ;Production

Tietze,in Bombardments of thin and thick W, Hg, Pb

Applications of Effective Field Theory Methods in Nuclear andTargets by 0 .4, 0 .8, 1 .2, 1 .8 and 2.5 GeV Protons

Particle PhysicsNucl. Instr. and Meth . i n Phys . Res . B170 (2000) 299-322 Prog . Part. Nucl. Phys . 44 (2000) 22320.90 .0 20.80 .0

IKP-00-11-066 IKP-00-11-075Leya, I . ; Lange, H.J . ; Lüpke, M . ; Neupert, U . ; Daunke, R. ;

Meyer, H . O ., Knutson, L . D ., Balewski, J . T, Dähnick, W. W,Fanenbruck, O . ; Michel, R . ; R6sel, R. ; Meltzow, B. ; Schiekel, T;

Doskow, J ., Häberli, W., Lorentz, B., Pollock, R. E., Pancella, P V.,Sudbrock, F. ; Herpers, U . ; Filges, D. ; Bonani, G. ; Dittrich-Hannen,

von Przewoski, B., Rathrnann, F., Rinckel, T, Saha, Swapan K.,B. ; Suter, M . ; Kubik, PW. ; Synal, H.A. : Schwartz, B ., Thorngren-Engblom, P, Wellinghausen, A ., andSimulation of the Interaction of GalacticMeteoroids :

ProtonsOn

withthe Production

Cosmic-Rayof Radionuclides in Thick Gabbro

Wise, TOberservation of a large longitudinal analyzing power in a nuclear

and Iron Targets Irradiated Isotropically with 1 .6 GeV Protons reaction .Phys . Left . B 480, 7 (2000)Meteoritics & Planetary Science 35 (2000) 287-318 20.45 .020.48 .0

IKP-00-11-067 IKP-00-11-076Lieder R.M ., Rzaca-Urban T, Jensen H.J., Gast W., Georgiev A.,

Mihailescu L ., Gast W., Lieder R.M ., Brands H ., Jäger H .Jäger H ., van der Meer E ., Droste Ch ., Morek T, Bazzacco D .,

The Influence of Anisotroplc Electron Drift Velocity on the SignalLunardi S., Menegazzo R ., Petrache C.M., Ross! Alvarez C ., Ur

Shapes ofclosed-end HPGe DetectorsC.A ., de Angelis G., Napoli D.R ., Venkova Ts., Wyss R.

Nucl . Instr. Methods A447 (2000) 350-360From Highly to Superdeformed Shapes: Study of '43Gd 20.10 .0Nucl . Phys . A671 (2000) 52-70 IKP-00-11-07720.10.0

Morsch H.P., Zupranski PStructure of the P� (1440 MeV) Resonance from a-p and x-N-ScatteringPhys . Rev. C61 (2000) 02400220.45 .0

IKP-00-11-078Moskal, P. et al . (for the COSY-11 Collaboration)Energy Dependence of the Near-Threshold Cross Section for thepp->ppil' ReactionPhys . Left. B474 (2000) 416-42220.50.0

IKP-00-11-079Moskal, F et al . (for the COSY-11 Collaboration)S-Wave ,f-Proton FSI ; Phenomenological Analysis of Near-Threshold Production of to , rl and if Mesons in Proton-ProtonCollisionsPhys . Left. B482 (2000) 356-36220.50 .0

IKP-00-11-080Moskal P (for the COSY-11 Collaboration)Proton-proton Collisions at Production ThresholdsProc. of the Workshop "Meson2000", Krakow, Poland,19:23.5.2000Act. . Phys . Pol. B31 (2000) 2277-228420.50 .0

IKP-00-11-081MOller G ., Meißner Ulf-G ., Steininger S.Renormalization of the Chiral Pion-Nucleon Lagrangian beyondnext-to-leading OrderAnn . Phys . (NY) 279 (2000)20.80 .0

IKP-00-11-082Nikolaev N . N ., Schafer W., Schwiete G.Multiple Pomeron Splitting in QCD-A Novel Anti-Shadowing Effectin Coherent Dijet Production on NucleiJETP Left . 72 (2000) 58320.80 .0

IKP-00-11-083Nikolaev N .N ., Schäfer W., Schwiete G.Coherent Production of Hard Dijets on Nuclei in QCDPhys. Rev. D63 (2000) 0340XX20.80 .0

IKP-00-11-084Nikolaev N.N ., Speth J ., Zoller VR.The Colour Dipole BFKL-Regge Expansion : From DIS on Protonsto Pions to Rise of Hadronic Cross Sections, Phys . Lett. B473(2000) 15720.80 .0

IKP-00-11-085Nikolaev N.N ., Speth J ., Zakharov B.G .Nuclear-Medium Modification of the Rho(1S)- and Rhoprim(2S)-Mesons in Coherent Photo- and Electroproduction: CoupledChannel AnalysisPhys . Atom . Nucl . 63 (2000) 146320.80 .0

IKP-00-11-086Nikolaev N.N .Diffractive Vector Mesons in DIS : Meson Structure an QCDActa Phys. Pol . 31 (2000) 248520.80 .0

IKP-00-11-087Novotny, R .,

Beck, R .,

Döring, W.,

Hejny, V,

Hofstaetter, A.,Korzhik, M . V., Metag, V., Ströher, H .Electromagnetic Calorimetry with PbWO4 in the Energy Regimebelow 1 GeVIEEE Transactions on Nuclear Science, Vol, 47, 4 (2000) 1499

20.50,0

IKP-00-11-088Novotny, R.,

Beck, R.,

Döring, W.,

Hejny, V,

Römer, K .,

and

Ströher, H .A compact and fast photon detector for COSY - status report on the

design study -IEEE NSS 2000, Lyon, France, October 200020.50 .0

IKP-00-11-089Oiler J.A.The Case of a WW Dynamical Scalar Resonance within a ChiralEffective Description ofthe strongly Interaction Higgs SectorPhys. Left. B477 (2000) 18720.80.0

IKP-00-11-90Oller J.A., Oset E ., Ramos A.Chiral Unitray Approach to Meson-Meson and Meson-BaryonInteractions and Nuclear ApplicationsProg . Part. Nucl . Phys. 45 (2000) 15720.80 .0

IKP-00-11-091Park B ., Rho M., Wirzba A ., Zahed I .Dense QCD : Overhauser or BCS Pairing?Phys . Rev. D62 (2000) 03401520.80 .0

IKP-00-11-092Petrache C.M ., Lo Bianco G ., Ward D., Galindo Uribarri A .,Spolaore P, Bozzacco D ., Kröll T, Lunordi S ., Menegozzo R ., RossiAlvarez C ., Mocchiavelli A., Clark R.M., Cromoz M., Follon P, LaneG.J ., Gast W., Lieder R.M ., Folconi G . Afonasjev A.V, RagnarssonI .Stable Triaxiality at the Highest Spins ' 38Nd und ' 39NdPhys . Rev. C61, 0113050(2000)20.10 .0

IKP-00-11-093Pienkowski, L . ; Bohne, W. ; Egidy, Tv. ; Galin, J . ; Goldenbaum, F ;Hilscher, D . ; Jahnke, U . ; Jastrzebski, J . ; Loft, B. ; Morjean, M . ;Pausch, G . ; Pdghaire, Polster, D. ; Proschitzki, S . ; Quednau, B . ;Rossner, H . ; Schmid, S . ; Schmid, W. :Vaporization and Multiframentation in the Reaction 1 .2 GeV p +Cu

and Ag .,Phys. Left. B472 (2000) 1520.48 .0

IKP-00-11-094Prasuhn, D. ; Dietrich, J . ; Maier, R . ; Stassen, R.; Stein, H . J . ;Stockhorst, H .Electron and stochastic Cooling at COSYNuclear Instruments & Methods in Physics ResearchA 441 (2000) 167-17420.38 .0

IKP-00-11-095Rho M., Wirzba A ., Zohed 1 .Generalized Pions in Dense QCDPhys . Lett. B473 (2000) 12620.80 .0

IKP-00-11-096Rho M., Shuryak E ., Wirzbo A., Zohed 1 .Generalized Mesons in Dense QCDNucl . Phys . A676 (2000) 27320.80 .0

IKP-00-11-097Roderburg E. (for the COSY-TOF Collaboration)

Measurement of the rl-Production in Proton-Proton Collisions with

the COSY-TOF-SpectrometerProc. ofthe Workshop "MESON 2000", Krakow, Poland, 19.-

23.5.2000Acta Phys. Pol . B31 (2000) 229920.45 .0

IKP-00-11-098Rzaca-Urban T, Pasternak A., Lieder R.M ., Urban W., Rejmund M .,

Marcinkowska Z., Marcinkowski R ., Utzeiman S., Jensen H.J., Gast

W., Jdger H., Bozzacco D ., Lunardi S., Medino N.H ., Menegozzo

R ., Povan P, Petroche C.M ., Rossi Alvarez C., de Angelis G.,

Napoli D.R., Zhu L., Dewald A., Kosemann S.

Study of Quadrupole Moments ofSuperdeformed Bands in '45Gd

Nucl . Phys . A677 (2000) 2520.10 .0

IKP-00-11-099Sa Borges J ., Soares Barbosa J ., Tonasse M ., Haidenbauer J .Two-loop Chiral Perturbation Theory and the Pion-Pion PhaseShiftsHadronic Journal 22, 617-623 (2000)20.80 .0

IKP-00-11-100Saito T-Y, Haidenbauer J .A Two-pion Exchange Three-Nucleon Force based on a Realistic-RN InteractionEuro . Phys . J . A7, 559-571 (2000)20.80 .0

IKP-00-11-101Schadow W., Sandhas W., Haidenbauer J ., Nogga A .Comparison of Triton Bound State Properties using DifferentSeparable Representations of Realistic PotentialsFew-Body-Systems 28, 241-258 (2000)20.80 .0

IKP-00-11-102Schadow W., Elster Ch ., Glbckle W.Three-Body Scattering below Breakup Threshold: An Approachwithout using Partial WavesFew-Body-Systems 28, 15 (2000)20.80 .0

IKP-00-11-103SchäferW., Nikolaev N.N ., SzczurekA ., Speth J .Inclusive Production of Forward Neutrons and the Pionic Content ofthe NucleonProc. of the Workshop "MESON2000", Krakow, Poland, 18 .-23 .5.2000, Acta Phys. Pol. Vol . 31 (2000) 2511-251520.80 .0

IKP-00-11-104Schwiete G .Higher Order Coulomb Corrections to the Primakoff Measurementofthe n LifetimeProc . of the Workshop "MESON2000", Krakow, Poland, 18 .-23.5.2000, Acta Phys . Pol . Vol . 31 (2000) 2437-244120.80.0

IKP-00-11-105Sewerin S ., Balewski J.T, Budzanowski A., Goodman C., GrzonkaD., Jarczyk L ., Jochmann M., Khoukaz A., Kilian K ., Köhler M.,Lister T., Moskal P., Oelert W., Quentmeier C ., Santo R ., SchepersG ., Seddik U ., Sefzick T, Smyrski J ., Strzalkowski A ., Wolke M .WOstner P, Eyrich W., Fritsch M., Haidenbauer J ., Hanhart C.,Stinzing F., Wilkin C .Near Threshold Hyperon-production at COSY-11 in the Reactionspp->PK'A and pp->pK+EoProceedings of the 15th International Conference on Particles andNuclei, PANIC'99, Uppsala, Sweden, 10.-16 .6.1999Nucl . Phys. A, Vol 663-664 (1-4) (2000) pp. 473-47620.50 .0

IKP-00-11-106Sibirtsev, A., Hejny, V, Str6her, H ., Cassing, W.Studying the w properties in pA collisions via the w->7roy decay,Phys . Lett. B 483 (2000) 40520.50 .0

IKP-00-11-107Siems, T,

Anagnostopoulos, D . F,

Borchert, G.,

Gotta, D.,Hauser, P, Kirch, K ., Simons, L. M ., EI-Khoury, P, Indelicato, P,Augsburger, M ., Chatellard, D ., Egger, J . -P.First Direct Observation of Coulomb Explosion during the Formationof Exotic AtomsPhys . Rev. Left . 84, 20 (2000) 457320.50 .0

IKP-00-11-108Smyrski J . et al. (for the COSY-11 Collaboration)Near-Threshold rl Meson Production in Proton-Proton CollisionsPhys. Left. B474 (2000) 182-18720.50 .0

IKP-00-11-109Stein, H . J., Krol, G ., Barsov, S ., Koptev, V.Application and methodological improvements to the floating-wiretechnique to characterize the magnetic properties of a spectrometerdipoleRev. Sci . Instc, submitted (2000)20.45.0

IKP-00-11-110Tarasov V., Baru V, Kudryavtsev A .Near-threshold Amplitude of Pion Deuteron Scattering : One-loopContributionPhys . Atom . Nucl . V63, 801 (2000)20.80 .0

IKP-00-11-111Vassiliev, A.,

Nelyubin, V,

Koptev, V.,

Kravtsov, P,

Lorentz, B.,Marik, H . J ., Mikirtytchiants, M ., Nekipelov, M ., Rathmann, F., Paetzgen . Schieck, H ., Seyfarth, H., and Steffens, E .24 Segment High Field Permanent Sextupole Magnets .Rev. Sci . Instrum . 7 1 (2000) 333120.45 .0

IKP-00-11-112Wagner, R . ; Bräutigam, W. ; Filges, D . ; Ullmaier, H . :The Project "European Spallation Neutron Source (ESS)" : Status ofR&D ProgrammePhysica B 276-278 (2000) 38-4420.90.0

IKP-00-11-113Walzt M .Isospin Violation in the Two Nucleon SystemProc. of the "MESON 2000" Conference, Krakow, Poland, 18:23.5.2000Acta Phys . Pol. Vol .31 (2000) 2709-271320.80 .0

IKP-00-11-114Weppner S.P., Garcia 0 ., Elster Ch .Sensitivities ofthe Proton-Neutron Elastic Scattering Observablesof 8He and 8He at Intermediate EnergiesPhys . Rev. C61, 044002-1 (2000)20.80.0

IKP-00-11-115Wissmann, F., Achenbach, P., Ahrens, J., Arends, H.-J ., Beck, R .,Bilger, R .,

Camen, M.,

Capitani, G . P,

Caselotti, G .,

Galler, G .,Grabmayr, P.,

Härter, F.,Hehl,T,

Held, E .,

Hejny, V.,

Jahn, 0.,Jennewein, P,

Kondratjev, R .,

Kossert, K .,

L'vov,

A. I .,Massone, A. M.,

Metag, V,

Natter, A .,

Novotny, R .,

Olmos

deLehn, V, Robbiano, A ., Rosenkranz, D., Sanzone, M., Schilling, E .,Schmidt, A ., Schumacher, M ., Seitz, B., Siodlaczek, U ., Smend, F,Str6her, H ., Vorwerk, H ., Walcher, Th., Weiss, J ., Wolf, M., Wolf, S .,Zapadtka, F.Compton scattering from the free and bound proton abovethresholdNucl . Phys. A663&664 (2000) 397c20.50 .0

IKP-00-11-116Wolf, M., Ahrens, J ., Beck, R ., Hejny, V, Kellie, J . D ., Kotulla, M .,Krusche, B .,Kuhr,V.,Leukel,R.,Metag,V.,Nacher,J. C.,Novotny, R.,Olmos

de

Le6n, V,

Owens, R. 0.,

Rambo, F.,Schmidt, A., Schumacher, M., Siodlaczek, U ., Str6her, H ., Weiß, J.,Wissmann, F.Photoproduction of neutral pion pairs from the protonEur. Phys . J. A 9, 5-8 (2000)20.50 .0

Proceedings, Reports

IKP-00-12-001Akushevich I ., Kuraev E.A ., Shaikhatdenov B.G ., Nikolaev N.N .DVCS in the Fragmentation Region of Polarized ElectronProceedings of Crimea Summer School, 27.5.-4.6.2000Yalta, Crimea, Ukraine, "Yalta2000 : New Trends in High-EnergyPhysics", pp . 65-6820.80 .0IKP-00-12-002Altmeier, M . ; Bauer, F. ; Bisplinghoff, J ; Busch, M . ; Büßer, K . ;Colberg, T ; Demirörs, L. ; Diehl, 0 . ; Dohrmann, F ; Engelhardt, H .P. ; Eversheim, P D . ; Felden, 0 . ; Gebel, R . ; Glende, M . ; Greiff, J. ;Groß-Hardt, R. ; Hinterberger, F. ; Jahn, R . ; Jonas, E . ; Krause, H . ;Langkau, R . ; Lindemann, l: ; Lindlein, J . ; Maier, R ., Maschuw, R . ;Meinerzhagen, A. ; Nähle, 0. ; Prasuhn, D. ; Rohdjeß, H . ; Rosendaal,D. ; Rossen von, P; Schirm, N . ; Schwarz, V. ; Scobel, W. ; Trelle, H .J . ; Weise, E . ; Wellinghausen, A . ; Woller, K. ; Ziegler, R .The EDDA CollaborationPp Elastic Scattering : New Results from EDDA (COSY)Nuclear Physics at Storage Rings, 200020.35 .0IKP-00-12-003Altmeier, M . ; Bauer, F ; Bisplinghoff, J ; Busch, M . ; Büßer, K. ;Colberg, T ; Demir6rs, L. ; Diehl, O . ; Engelhardt, H . P ; Eversheim, PD. ; Felden, 0 . ; Gebel, R . ; Glende, M . ; Greiff, J. ; Hinterberger, F;Jonas, E.; Krause, H. ; Lindemann, T. ; Lindlein, J. ; Maier, R . ;Maschuw, R. ; Meinerzhagen, A. ; Prasuhn, D . ; Rohdjeß, H . ;Rosendaal, D . ; Rossen von, P ; Schirm, N . ; Schwarz, V.; Scobel,W. ; Trelle, H . J . ; Weise, E. ; Wellinghausen, A .; Ziegler, R .The EDDA CollaborationExcitation Functions of the Analyzing Power in pp Scattering from0.45 to 2.5 GeVPhysical Review Letters (2000)20.35.0IKP-00-12-004Anagnostopoulos, D . F,

Borchert, G.,Egger,J. - P,

Gotta, D .,Hennebach, M ., Indelicato, P, Liu, Y W., Manil B ., Nelms, N. andSimons, L. M .Acta Phys. Pol . B, Vol . 31, 10 -11 (2000) 221920.45.0IKP-00-12-005Barnes T.Hybrids BaryonsProc. of the COSY-Workshop "Baryons Exitations",Forschungszentrum JDlich, Germany, 2:3.5.2000, ads . T Barnes,H .-R Morsch, Schriften d . Forschungszentrums Jülich, ReiheMaterie und Material, Vol . 6 (2000) 121-13120.80 .0

IKP-00-12-006Barnes T.HybridsLectures ofthe COSY Workshop "Baryons Exitations", eds . T.Barnes, H.P. Morsch, Forschungszentrum Jülich, Matter andMaterials, Vol. 6, 2000,121-13120.80 .0

IKP-00-12-007Barnes T, Morsch H.P.Baryons ExitationsMatter and Materials, Vol. 6, 2000, Forschungszentrum JDlich,Germany, 2.-3:5.200020,80.0

IKP-00-12-008Barsov, S .,

Bechstedt, U .,

Borchert, G.,

Borgs, W.,

Büscher, M .,Debowski, M.,

Erven, W.,

Eßer, R.,

Fedorets, P,

Gotta, D .,Hartmann, M ., Junghans, H ., Kacharava, A ., Klehr, F., Koch, H . R.,Komarov, V. I .,

Koptev, V.,

Kulessa, P,

Kulikov, A.,

Kurbatov, V,Macharashvili, G.,

Maier, R .,

Mikirtytchiants, S .,

Merzliakov, S .,Müller, H .,

Mussgiller, A.,

Nioradze, M .,

Ohm, H.,

Petrus, A.,Prasuhn, D .,

Pysz, K.,

Rathmann, F.,

Rimarzig, B .,

Rudy, Z.,Schleichert, R .,

Schneider, Chr.,

Schneider, H .,Schult,0. W. B,Seyfarth, H ., Sistemich, K ., Stein, H. J ., Ströher, H . for the ANKEcollaborationFirst Results on Strangeness Production from the ANKE FacilityAIP Conf. Proc. 512 (2000) 13820,45.0

IKP-00-12-009Barsov, S.,

Bechstedt, U .,

Borchert, G., Borgs, W.,

Bescher, M .,Debowski, M .,

Erven, W.,

Eßer, R .,

Fedorets, F,

Gotta, D.,Hartmann, M., Junghans, H ., Kacharava, A., Klehr, F, Koch, H, R.,Komarov, V. I .,

Koptev, V,

Kulessa, P,

Kulikov, A.,

Kurbatov, V,Macharashvili, G .,

Maier, R .,

Mikirtytchiants, S .,

Merzliakov, S.,Müller, H .,

Mussgiller, A .,

Nioradze, M .,

Ohm, H.,

Petrus, A.,Prasuhn, D .,

Pysz, K.,

Rathmann, F.,

Rimarzig, B.,

Rudy, Z .,Schleichert, R .,

Schneider, Chr.,

Schneider, H.,Schult,0. WB,Seyfarth, H ., Sistemich, K., Stein, H . J., Ströher, H. for the ANKEcollaborationFirst results from subthreshold K'-production measurements withANKEProc. XVth Particles And Nuclei International Conf. (PANIC 99),10 -16 June 1999, Uppsala, Sweden ; Nucl . Phys. A, 663 - 664,(2000)1107c20.45.0

IKP-00-12-010Barsov, S .,

Koptev, V.,

Bechstedt, U .,

Buescher, M .,

Krol, G .,Sagefka, Th ., and Stein, H. J .Dipole Field Characterization by Floating Wire and Field Map RayTracingProc. 16'° International Conference on Magnetic Technology, PonteVedra Beach, USA, 26 Sept . - 2 Oct . 1999, in Trans . AppliedSupercond. 10 (2000) 146220.45.0

IKP-00-12-011Barsov, S .,

Bechstedt, U .,

Borchert, G ., Borgs, W., Bescher, M .,Debowski, M.,

Erven, W.,

Eßer, R .,

Fedorets, P,

Gotta, D.,Hartmann, M., Junghans, H ., Kacharava, A ., Klehr, F, Koch, H . R .,Komarov, V. I .,

Koptev, V,

Kulessa, P,

Kulikov, A .,

Kurbatov, V.,Macharashvili, G .,

Maier, R .,

Mikirtytchiants, S .,

Merzliakov, S.,Müller, H .,

Mussgiller, A.,

Nioradze, M .,

Ohm, H.,

Petrus, A.,Prasuhn, D.,

Pysz, K.,

Rathmann, F,

Rimarzig, B.,

Rudy, Z .,Schleichert, R .,

Schneider, Chr.,

Schneider, H.,Schult,0. W. B,Seyfarth, H., Sistemich, K ., Stein, H. J., Ströher, H. for the ANKEcollaborationSubthreshold K`-Production Studies with ANKE at COSY-JülichProc. 7`" Conf. on the Intersections of Particle and Nuclear Physics(CIPANP 2000), Quebec, Canada, 22-28 May 200020.45 .0IKP-00-12-012Betiged M ., Bojowald J ., Budzanowski A ., Chatterjee A., Ernst J .,Freindl L ., Frekers D ., Garske W., Grewer K., Hamacher A., IlievaJ ., Jarczyk L., Kemmerling G ., Kilian K ., Kliczewski S., KIimala W.,Kolev D ., Ketsarova T, Lieb J., Machner H ., Magiera A., Nann H .,Pentchev L ., Plendl H.S ., Protic D., Razen B., von Rossen P, RoyB.R ., Sludak R ., Smyrskl J ., Srlkantiah R.V, Strzalkowski A.A.,Tsenov R ., Zolnierczuk P.A ., Zwoll K .Meson Production in p+d ReactionsProc. "STORI99" Conference, Bloomington, USA 2000, AIP Conf.Proc. 512 (2000) 6020.45 .0IKP-00-12-013Büscher, M.COSY-News 10 (2000)20.45 .0IKP-00-12-014Büscher, M ., Kleber, VProceedings of the �Workshop on ao Physics with ANKE", Moscow,Russia, July 13 -14, 2000Berichte des Forschungszentrums Jülich 3801, ISSN 0944-2952,Institut für Kernphysik Jü1-380120.45 .0

IKP-00-12-015Cloth, P ; Filges, D, and the members ofthe ZEUS Collaboration :Search for Resonances Decaying to e'-Jet in e`p Interactions atHERAReport, DESY-00-023, February 200020.48.0

IKP-00-12-016Cloth, P ; Filges, D . and the members of the ZEUS Collaboration :The Qz Dependence of Dijet Cross Sections in yp Interactions atHERAReport, DESY-00-017, Feb. 200020.48 .0

IKP-00-12-017Cloth, P; Filges, D. and the members of the ZEUS Collaboration:

Measurement of Inclusive D+Y Photoproduction at HERAReport, DESY-00-023, Feb . 200020.48 .0

IKP-00-12-018Cloth, P. ; Filges, D. and the members ofthe ZEUS Collaboration :Measurement of Azimuthal Asymmetries in Deep InelasticScatteringReport, DESY-00-040, March 200020.48 .0

IKP-00-12-019Cloth, P ; Filges, D. and the members of the ZEUS Collaboration :Measurement of the Proton Structure Function FZ at Very Low Q2 atHERAReport, DESY-00-071, May 200020.48 .0

IKP-00-12-020Cloth, P. ; Filges, D. and the members of the ZEUS Collaboration :Measurement of exclusive w electroproduction at HERAReport, DESY-00-084, June 200020.48.0

IKP-00-12-021Cloth, P. ; Filges, D . and the members ofthe ZEUS Collaboration:A Search for Resonance Decays to ü -Jet in e*p Scattering atHERAReport, DESY-00-133, September 200020.48.0

IKP-00-12-022Cloth, P; Filges, D . and the members of the ZEUS Collaboration :Measurement of Dijet Cross Sections for Events with a LeadingNeutron in Photoproduction at HERAReport, DESY-00-142, October 200020.48.0

IKP-00-12-023COSY-Newspublished by the FZJ in Cooperation with CANU, the COSY UserOrganisation ofthe UniversitiesNo . 8, May 200020.45 .0

IKP-00-12-024Crescenti ; M . ; Etzkorn, F. -J . ; Schnase, A . ; Primadei, G . ; Susini, A. ;(Tera Consultant)The VITROVACO RF Cavity in the TERAIPIMMS MedicalSynchrotronProceedings ofthe 7"' European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.30.0

IKP-00-12-025Dietrich, J . ; Bojowald, J. ; Labus, H . ; Lawin, H. ; Mohos, I .Fast Kicker Extraction at COSY-JülichProceedings of the 7' h European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.38 .0

IKP-00-12-026Elster Ch ., Schadow W., Glückle W.Few-Body-Calculations - An Approach without Partial WavesDPG-Frühjahrstagung, Dresden, Germany, 20-24.3.2000, Verhandl.DPG(VI) 35, 208 (2000), HK 8.420.80 .0

IKP-00-12-027Gasparian A., Haidenbauer J., Hanhart C., Kondratyuk A ., Speth J.Near Threshold Aand Eo Production in pp CollisionsProc . i n "Nuclear Physics at Storage Rings", AIP Conference, No .512 (2000), pp . 120-122, eds . H.O. Meyer, P Schwandt20.80.0

IKP-00-12-028Gast W., Lieder R.M., Mihailescu L ., Rossewij M .Digital Signal Processing for y-Ray Tracking based on PPADCHardwareVerhandl . DPG (VI) 35, 218 (2000)20.10 .0

IKP-00- 12-029Gast W., Lieder R.M . Mihailescu L ., Rossewij M ., Georgiev A., SteinJ .Digital Signal Processing and Algorithms for Gamma-Ray-TrackingBook of Abstracts, "IEEE Nuclear Science Symposium and MedicalImaging Conf." Lyon, France, (2000) p . 10720.10.0

IKP-00-12-030Gillftzer A .N" Excitations in p- ScatteringProc. of the COSY-Workshop "Baryons Exitations",Forschungszentrum Jülich, Germany, 2:3.5.2000, eds . T Barnes,H.P. Morsch, Schriften d. Forschungszentrums Jülich, ReiheMaterie und Material, Vol . 6 (2000) 173-18520.45 .0

IKP-00-12-031Gotta, D .Measurement of the ground-state shift and width in picnic hydrogento the 1 % level: A new proposal at PSIProc . of the Eighth International Symposium on Meson-NucleonPhysics and the Structure of the Nucleon, (MENU'99)Zuoz, Engadine, Switzerland, 15 - 21 August 1999, nN Newsletterno. 15, December 1999, p . 27620.50 .0

IKP-00-12-032Haidenbauer, J ., Baru V., Gasparian A ., Hanhart C ., Nakayama K .,Speth J .Mesonproduktion in Nukleon-Nukleon KollisionenDPG-Frühjahrstagung, Dresden, Germany, 20-24.3.2000, Verhandl.DPG(VI) 35,208 (2000), HK 820.80.0

IKP-00-12-033Khoukaz A. (for the COSY-11 Collaboration)Near Threshold Heavy Meson Production in pp- and pd-Collisionsat the Experiment COSY-11International Workshop XXVIII on Gross Properties of Nuclei andNuclear Excitations, Hirschegg, Austria, 16:22.1 .2000Proceedings'Hadrons in Dense Matter', GS1 Darmstadt,ISSN 0720-8715, p. 35-3920.50 .0

IKP-00-12-034Khoukaz A. (for the COSY-11 Collaboration)Schwellennahe Mesonenproduktion an COSY-11DPG-Frühjahrstagung, Dresden, Germany, 20.24.3.2000,Verhandlungen der DPG (VI) 35, 247 (2000), HK 27.420.50.0

IKP-00-12-035Kilian K.Study of Hyperon Resonances with TOFProc. of the COSY-Workshop "Baryons Exitations",Forschungszentrum Jülich, Germany, 2.-3 .5 .2000, eds . T Barnes,H.P. Morsch, Schriften d . Forschungszentrums Jülich, ReiheMaterie und Material, Vol, 6 (2000) 187-18920.45.0

IKP-00-12-036Krewald S .Structure of the Roper Resonance described by Meson-BaryonDynamicsLectures ofthe COSY Workshop "Baryons Exitations", eds . T.Barnes, H.P. Morsch, Forschungszentrum Jülich, Matter andMaterials, Vol. 6, 2000,121-13120.80.0

I KP-00-12-037Krewald S .Structure of the Roper Resonance Described by Meson BaryonDynamicsProc . of the COSY-Workshop "Baryons Exitations",Forschungszentrum Jülich, Germany, 2.-3 .5.2000, eds . T. Barnes,H.-P. Morsch, Schriften d . Forschungszentrums Jülich, ReiheMaterie und Material, Vol . 6 (2000) 65-7120.80.0

IKP-00-12-038Kulessa, F,

Rudy, Z .,

Cassing, W.,

Hartmann, M .,

Jarczyk, L .,Kamys, B.,

Koch, H . R.,

Ohm, H.,

Pysz, K .,

Ströher, H .,Strzalkowski, A .Interaction of Strange Particles with NucleonsActa Phys . Pol. B, Vol . 31, 10 -11 (2000) 224320.45.0

IKP-00-12-039Lieder R.M ., Rzaca-Urban l:, Brands H ., GastW., Jäger H.M .,Mihailescu L. Pytel Z ., Urban W., Morek T, Droste Chr., Chmel S .,Bazzacco D., Falconi G ., Menegazzo R., Lunardi S ., Rossi AlvarezC., de Angelis G ., Famea E., Gadea A., Napoli D.R., Podolyak Z.Study of Oblate Dipole and Triaxial Quadrupole Bands in 1° Gd withEUROBALLVerhandl . DPG (VI), 35, 234 (2000)20.10 .0

IKP-00-12-040Lieder R.M. and the Gamma-Ray Tracking Detector CollaborationThe TMR Network Project "Development of Gamma-Ray TrackingDetectors"Verhandl. DPG (VI) 35,201 (2000)20.10 .0

IKP-00-12-041Lorentz, B . ; Bechstedt, U . ; Bräutigam, W. ; Dietrich, J . ; Gebel,R . ; .Henn, K. ; Lehrach, A . ; Maier, R. ; Martin, S . ; Prasuhn, D . ;Rossen, v. P ; Schnase, A. ; Schneider, H . ; Stassen, R. ; Stockhorst,H . ; Tülle, R .Status des Mittelenergiebeschleunigers COSYDPG Tagung Dresden, 20.3 . - 24.3.200020.30.0

IKP-00-12-042Machner H . (for the GEM-Kollaboration)Gleichzeitige Messung neutraler und gelader Pionen in Proton-Proton WechselwirkungDPG-Frühjahrstagung, Dresden, Germany, 20.24.3.2000,Verhandlungen der DPG (VI) 35, 247 (2000), HK 27.420.45 .0

IKP-00-12-043Magiera A . (for the GEM-Kollaboration)Isospin Symmetry breaking in p+d->3H+rz`PHe+n ReactionsDPG-Frühjahrstagung, Dresden, Germany, 20.-24.3 .2000,Verhandlungen der DPG (VI) 35, 229 (2000)20.45.0

IKP-00-12-044Magiera A ., Betigeri M., Bojowald J ., Budzanowski A., ChatterjeeA ., Ernst J ., Freindl L., Frekers D ., Garske W., Grewer K.,Hamacher A., Ilieva J., Jarczyk L ., Kemmerling G ., Kilian K.,Kliczewski S ., Klimala W., Kolev D., Kutsarova T, Lieb J ., MachnerH., Nann H., Pentchev L ., Plendl H.S., Protic D., Razen B ., vonRossen P., Roy B.R ., Siudak R ., Smyrski J ., Srikantiah R.V,Strzalkowski A.A ., Tsenov R., Zolnierczuk PA ., Zwoll K.Reaction Mechanism and Isospin Symmetry breaking inpd-+3Hen°/3H7c" ReactionsProc . "9th Intern . Conference Nuclear Reaction Mechanisms,Varenna, Italy 2000, Ricerca Scientifica ed EducazionePermanente, Suppl . 115 (2000) 27520.45 .0

IKP-00-12-045Martin, S. ; Bräutigam, W. ; Glenda, M . ; Maier, R. ; Schug, G . ;Senichev, Y, Zaplatin, E. ; Pichoff, N . (CEA) ; Safa, H . (CEA)System Optimisation for a Superconducting Linac for the EuropeanSpallation Source ESSProceedings ofthe 7`h European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.91 .0

IKP-00-12-046Meißner Ulf-G .Chiral QCD : Baryon DynamicsContribution to the Festschrift in honor of Boris loffe, one chapter ofthe "Handbook of QCD", M . Shifman (ad .), World Scientific,Singapore, 200020.80 .0

IKP-00-12-047Mihailescu L., Gast W., Lieder R.M ., Rossewij M .On-line Pulse Shape Analysis Algorithms for y-RayTrackingVerhandl . DPG (VI) 35, 215 (2000)20.10.0

IKP-00-12-048Morsch H.-P.Structure of the P11(1440 MeV) Resonance from a-p and 7E-N-ScatteringProc . of the COSY-Workshop "Baryons Exitations",Forschungszentrum Jülich, Germany, 2:3.5.2000, ads . T Barnes,H.P. Morsch, Schriften d . Forschungszentrums Jülich, ReiheMaterie und Material, Vol . 6 (2000) 39-5220.45 .0

IKP-00-12-049Rathmann, F.Review of Polarized Internal Gas TargetsIn Meyer, H . O . and Schwandt, P., editors, Proc . of the 4`h Int. Conf.On Physics at Storage Rings, volume 512 of ConferenceProceedings, page 193, American Institute of Physics, 2000 .20.45 .0

IKP-00-12-050Rathmann, F,

Düren, M.,

Jansen, P,

Klehr, F,

Meyer, H. O .,Martin, S ., Rith, K ., Seyfarth, H ., Steffens, E ., and Ströher, H .Study of Heavy Meson Production in NN Collisions with PolarizedBeam and Target at COSYIn Proc. of the 14th Int . Spin Physics Symposium, ConferenceProceedings, to be published, 2000 .20.45.0

IKP-00-12-051Rzaca-Urban T, Pasternak A., Lieder R.M ., Urban W., Rejmund M.,Utzelman S ., Jensen H.J ., Gast W., Jäger H ., Bazzacco D.,Menegazzo R., Lunardi S ., Rossi Alvarez C ., de Angelis G ., MedinoN ., Napoli D.R .Study ofQuadrupole Moments of Superdeformed bands in 1"5GdVerhandl . DPG (VI) 35,214 (2000)20.10 .0

IKP-00-12-052Quentmeier C . (for the COSY-11 Collaboration)Untersuchung der Reaktion pp->ppK'K" nahe derProduktionsschwelle am Experimentaufbau COSY-11DPG Frühjahrstagung, Dresden, Germany, 20.-24.3 .2000,Verhandlungen der DPG (VI) 35, 229 (2000), HK 15 .820.50.0

IKP-00-12-053Schnase, A. ; Bechstedt, U . ; Böhnke, M . ; Dietrich, J . ; Etzkorn, F.J . ;Henn, K . ; Maier, R. ; Papureanu, S . ; Prasuhn, D .; Schneider, H . ;Stassen, R . ; Stockhorst, H . ; Tülle, R .Experience with a Broadband Cavity at COSYProceedings of the 7th European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.30.0

IKP-00-12-054Senichev, Y Bräutigam, W. ; Martin, S. ; Zaplatine, E .Normal and Superconducting Parts of Linear Accelerators forNeutron Spallaboln Sources: Main Problems and Possible SolutionsProceedings ofthe 7th European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.91 .0

IKP-00-12-055Siodlaczek, U ., Achenbach, P, Ahrens, J ., Arends, H.-J., Beck, R .,

Bilger, R ., Clement, H., Hejny, V, Kotulla, M ., Krusche, B ., Kuhr, V,

Leukel, R., Metag, V, Novotny, R ., Olmos des Le6n, V, Rambo, F,

Schepkin, M ., Schmidt, A ., Schumacher, M., Ströher, H .,

Wagner, G. J ., Walcher, Th ., Weiß, J ., Wissmann, F., Wolf, M.

Measurement of coherent and incoherent 7r° photoproduction off the

deuteron with tagged photons up to the A regionNucl . Phys . A633&664 (2000) 428c20.50 .0

IKP-00-12-056Stockhorst, H . ; Bechstedt, U . ; Dietrich, J ; Gebel, R . ; Henn, K . ;

Lorentz, B . ; Lehrach, A . ; Maier, R. ; Prasuhn, D . ; Rossen, v. P ;

Schnase, A. ; Schneider, H . ; Stassen, R . ; T611e, R .

The Medium Energy Proton Synchrotron COSYProceedings ofthe 7t° European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.30 .0

IKP-00-12-057Str6her, H.Meson Production with Various ProbesActa Phys . Pol. B, Vol . 31, 10 -11 (2000) 233320.45.0

IKP-00-12-058Str6her, H .Measurement fo Neutral Decays of N"s at COSYWorkshop on "Baryon Excitations", Jülich, 2 - 3 May 200020.45 .0

IKP-00-12-059Str6her, H.Meson Photproduction with TAPS at MAMIIX Seminar Electromagnetic Interactions of Nuclei at Low andMedium Energies", Moscow, 20 - 22 Sept. 200020.50.0

IKP-0012-060Typel S ., Wolter H ., Baur G .Indirekte Methoden in der nuklearen Astrophysik: Coulombaufbruchund Trojan-Horse-MethodeDPG-Frühjahrstagung, Dresden, Germany, 20-24.3.2000, Verhandl .DPG(V1) 35,250 (2000) HK 30.520.80 .0

IKP-00-12-061Whisnant, S . S .,

Ardashev, K .,

Blecher, M.,

Caracappa, A .,D'Angelo, A.,

Didelez, J . P,

Deininger, R .,

Hicks, K .,

Hoblit, S .,Honig, A ., Khandaker, M., Kistner, O ., Kuczewski, A ., Lincoln, F,Lindgren, R .,Lehmann,A.,

Lowry M.,

Lucas,

M.,

Meyer, H.,Micelli, L, Preedom, B . M., Norum, B., Saitoh, T, Sandorfi, A . M .,Schaerf, C., Str6her, H ., Thorn, C ., Wang, K. and Wei, X .The Polarized HD Ice Target at LEGSWorld Scientific (2000)20.50 .0

IKP-00-12-062Wolke M . (forthe COSY-11 Collaboration)Hyperon Production at the COSY-11 FacilityInternational Workshop XXVIII on Gross Properties of Nuclei andNuclear Excitations, Hirschegg, Austria, 16.-22.1.2000Proceedings'Hadrons in Dense Matter', GSI Darmstadt,ISSN 0720-8715, p. 27-3420.50 .0

IKP-00-12-063Wolke M. (for the COSY-11 Collaboration)Exclusive Strangeness Production in Proton-Proton Scattering atCOSY17 . Students' Workshop on Electromagnetic Interactions,Sonderforschungsbereich 443 'Vielk6rperstruktur starkwechselwirkender Systeme' der DeutschenForschungsgemeinschaft (DFG), Bosen (Saar), Germany,September 200020.50 .0

IKP-00-12-064Yoshii, M . ; Ohmori, C.; Mori, Y; Kek; Schnase, A.MA RF Cavity for the KEK 12 GEV PSProceedings of the 7`h European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.30 .0

IKP-00-12-065Zaplatin, E . ; Bräutigam, W.; Felden, O. Maier, R . ; Martin, S .;Stassen, R.Superconducting RF Cavity Development for ESSProceedings of the 7'h European Particle Accelerator Conference(EPAC), 26 June to 30 June 2000, Wien20.91 .0

Invited Talks

IKP-00-21-001Barnes THybrids BaryonsCOSY-Workshop "Baryons Exitations", Forschungszentrum Jülich,Germany, 2.-3 .5.200020.80 .0

IKP-00-21-002Baur G .Photon-photon and Photon-Hadron Interactions in PeripheralCollisions : From RHIC to LHCCMS Heavy Ion Meeting, St . Petersburg, Russia, 11 :14.6.200020.80 .0

IKP-00-21-003Baur G.Electromagnetic Dissociation as a Tool for Nuclear Structure andAstrophysicsInt. School of Nuclear Physics, 22"° Course : Radioactive Beams inNuclear and Astrophysics, Erice, Sicily,16:24.9.200020.80.0

IKP-00-21-004Baur G .The Past and Future of Coulomb Dissociation in Hadron- andAstrophysicsNATO Advances Study Institute "Nuclei far from Stability andAstrophysics", Predeal, Rumania, 28.8.-B .9.200020.80 .0

IKP-00-21-005BOttiker PDispersion Relations and Chiral Perturbation TheoryInternational Conference on "Conference Chiral Dynamics : Theoryand Experiment", Newport News, USA, 17.-22 .7.200020.80 .0

IKP-00-21-006Dietrich, J .Lectures given during the "Accelerator School 2000":Fundamental of Particle Accelerator PhysicsResearch and Development Center forAdvanced Technology, 2.9 .- 12.9.2000,Yogyakarta,Indonesia20.30 .0

IKP-00-21-007Elster Ch .Faddeev Calculations without Partial Wave DecompositionWorkshop 'Towards a Solution for 4HeGraduiertenkolleg Erlangen-Regensburg, Erlangen, Germany,19 .1 .200020.80 .0

IKP-00-21-008Elster Ch .Faddeev Calculations in Nuclear PhysicsWorkshop on Computational Methods for Few-Body DynamicalSytems, NIST Gaithersburg, USA,15-17.11 .200020.80 .0

IKP-00-21-009Elster Ch .Three Body Bound States : Nonrelativistic and RelativisticCalculations without Angular Momentum DecompositionInternational Symposium on "Nuclear Physics", Bhabha AtomicResearch Centre, Tombay, Mumbai, 18.-22 .12.200020.80.0

IKP-00-21-010Epelbaum E .Chiral Dynamics in the Few Nucleon SystemXVII European Conference on Few-Body Problems in Physics,Evora, Portugal, 11 .-16 .9.200020.80 .0

IKP-00-21-011Fettes N .Isospin Violation in 7c7c and icN Systems

International Conference on "Conference Chiral Dynamics: Theoryand Experiment", Newport News, USA, 17.-22 .7.200020.80 .0

IKP-00-21-012Filges, D . ; Enke, M . ; Galin, J . ; Goldenbaum, F. ; Herbach, C.M . ;Hilscher, D ., Jahnke, U .; Letourneau, A . ; Lott, B . ; Neef, R.-D . ;Nünighoff, K . ; Paul, N . ; P6ghaire, A . ; Pienkowski, L . ; Pohl, C . ;Schaal, H. ; Schröder, U . ; Sterzenbach, G. ; Tietze, A . ; Tishchenko,V ; Toke, J . ; Wohlmuther, M . :Spallation Reactions and Energy Deposition in Heavy TargetMaterials : Com?arison of Measurements and MC-Calculations(CANSXV, 15'

Meeting of the Int. Collaboration on AdvancedNeutron Sources, Tsukuba, Japan, Nov. 6-9, 200020.90 .0

IKP-00-21-013Filges, D . :Summary Report of the Working Group Session:"Code Systems, Cross Sections and Kernels"CCANS-XV, 15'° Meeting of the Int. Collaboration on AdvancedNeutron Sources, Tsukuba, Japan, Nov. 6-9, 200020.48.0

IKP-00-21-014Filges, D.; Neef, R.D. ; Schaal, H. ; Sterzenbach, G . :The HERMES Monte Carlo Program System a Versatile Tool forSpallation Physics and Detector ApplicationsMC2000, Int . Conf. on Advanced Monte Carlo for RadiationPhysics, Particle Transport Simulation and Applications, Lissabon,Portugal, Oct. 23-26, 200020.90 .0

IKP-00-21-015Filges, D . ; Gudowski, W. :Summary and Highlights of Hadronic Sessions, Speculations andPerspective ViewsMC2000, Int. Conf . on Advanced Monte Carlo for RadiationPhysics, Particle Transport Simulation and Applications, Lissabon,Portugal, Oct . 23-26, 200020.48.0

IKP-00-21-016Filges, D . :Introduction and Aim of the MeetingSARE-51SATIF-5 Meeting Models and Codes for Spallation NeutronSourcesOECD-Headquarters, Paris, France, July 17-18,200020.90 .0

IKP-00-21-017Filges, D . :The European Spallation Neutron Source - ESS - A MaterialScience Research Tool for the Next MilleniumPhysikalisches Kolloquium, Univ. Krakau, Polen, Feb. 17, 200020.90.0

IKP-00-21-018Goldenbaum, F. :The European Spallation Source ESS: A next generation neutronsource for EuropeXXXI . Arbeitstreffen Kernphysik in Schleching/Obb., März 8-16 .,200020.90 .0

IKP-00-21-019Goldenbaum, F. for the NESSI-Collaboration :Models and Codes for Spallation Neutron Sources. Validation ofHadron-Nucleus Transport Models in the GeV RangeSARE-5/SATIF-5 Meeting, OECD-Headquarters, Paris, France, July17-18,200020.90 .0

IKP-00-21-020Goldenbaum, F. ; Enke, M . ; Filges, D . ; Galin, J . ; Herbach, C;M . ;Hilscher, D . ; Jahnke, U . ; Letourneau, A. ; Loft, B . ; Neef, R.D . ;Nünighoff, K. ; Paul, N . ; Pöghaire, A . ; Pienkowski, L . ; Schaal, H . ;

Schröder, U . ; Sterzenbach, G. ; Tietze, A . ; Tishchenko, V ; Toke, J . ;Wohlmuther, M . :Validation of MC-Models of Spallation Reactions in Thin and Thick

Targets In the GeV Range

MC2000, Int. Conf. on Advanced Monte Carlo for RadiationPhysics, Particle Transport Simulation and Applications, Lissabon,Portugal, Oct . 23-26, 200020.90 .0

IKP-00-21-021Gotta, D .Precision Spectroscopy ofX-rays from Antiprotonic AtomsHydrogen Atom II: Precise physics of simple atomic systems (PSAS2000),Castiglione della Pescaia, Italy, 1 s'-3 °̀ June 200020.50.0

IKP-00-21-022Gotta, D .Pionic HydrogenVlll . International Oberjoch Meeting on BrokenSymmetries and Meson-Nuclear Physics,Oberjoch, Germany, 4 - 9 September 200020.50.0

IKP-00-21-023Gotta, D.Precision Determination of the sN s-wave Scattering Lengths fromPionic Hydrogen : A new Proposal at PSISeminar Institut für Theoretische Physik, Universität Bern,18 January 200020.50 .0

IKP-00-21-024Haidenbauer J .Mesonproduktion in der Nukleon-Nukleon StreuungUniversity of Graz, Austria, 21 .6.200020.80 .0

IKP-00-21-025Haidenbauer J .Description of the ao/fo (980) Mesons with the Jülich ModelWorkshop on "a o Physics with ANKE", I.TEP, Moscow, Russia, 13 .-14.7.200020.80 .0

IKP-00-21-026Hemmert TR .Nucleon Compton Scattering in Chiral Effective TheoriesInternational Conference on "Conference Chiral Dynamics : Theoryand Experiment", Newport News, USA, 17.22.7.200020.80 .0

IKP-00-21-027Hemmert TR .Low Energy Spin Structure of The Nucleon beyond Leading OrderInternational Conference "GDH2000" Mainz, Germany,14-17.6 .200020.80 .0

IKP-00-21-028Hilscher, D . ; Herbach, C.-M . ; Jahnke, U . ; Tishchenko, V ; Enke, M . ;Filges, D . ; Goldenbaum, F; Neef, R.-D. ; Nünighoff, K . ; Paul, N . ;Schaal, H .; Sterzenbach, G. ; Letourneau, A . ; Böhm, A . ; Galin, J . ;Lott, B . ; P6ghaire, A. ; Pienkowski, L. :Helium Production for 0.8-2.5 GeV Proton Induced SpallationReactions, Damage Induced in MetallicWindow MaterialsInt. Materials Workshop-4, Schruns, Österreich, Oct. 8-13, 200020.90.0

IKP-00-21-029Ivanov I.Diffractive Vector Meson Production in a Unified K-FactorizationApproach8' International Workshop on Deep Inelastic Scattering and QCD-

DIS2000", Liverpool, United Kingdom, 25-30.4 .2000

20.80 .0

IKP-00-21-030Ivanov I .Anatomy ofthe Proton Structure Functions in x- Factorization

8'h International Workshop on Deep Inelastic Scattering and QCD-

DIS2000", Liverpool, United Kingdom, 25.-30 .4.2000

20.80 .0

IKP-00-21-031Kamerdzhiev S .Mechanisms ofthe Giant Resonance ExcitationsIX Intern. Seminar "Electromagnetic Interactions of Nuclei at Lowand Medium Energies", Moscow, Russia, 20:22.9.200020.80 .0

IKP-00-21-032Kamerdzhiev S .On Two Mechanisms of Supertluidity in Atomic NucleiWorkshop "New Perspective of Pairing Phenomena in NuclearSystems", Trento, Italy, 31 .1 .-11 .2.200020.80 .0

IKP-00-21-033Kilian, K.Meson Baryon Systems and Interactions16'" Int. Conf. on Few-Body Problems in Physics, TaipeilTaiwan, 6.-10.3.200020.45 .0

IKP-00-21-034Kilian K.New Results from COSYIntern . Conference "Quark-Nuclear-Physics (QNP), Adelaide,Australia, 21 .-25 .2.200020.45.0

IKP-00-21-035Kilian K.Strangeness Production at COSYColloquium, University of Torino, Italy, 3 .4.200020.45.0

IKP-00-21-036Kilian K.Associated Strangeness Production at COSYVII Int. Conf. on "Hypemuclei and Strange Particle hysics", Torino,Italy, 23.27.10.200020.45.0

IKP-00-21-037Lieder R.M.Gamma-Ray Tracking ArraysIntern . School of Nuclear Physics, 22th Course, Radiactive Beamsfor Nuclear and Astrophysics, Erice, Italy, 21 .9.200020.10.0

IKP-00-21-038Krewald S .Structure described by Meson-Baryon DynamicsCOSY-Workshop "Baryons Exitations", Forschungszentrum Jülich,Germany, 2.3.5.200020.80 .0

IKP-00-21-039Krewald S.What is the Structure ofthe Roper Resonance3`° German-Taiwanese Symposium, Taipei, Taiwan,3.-6.3.200020.80 .0

IKP-00-21-040Krewald S .Meson Production in Hadronic ReactionsConference "Fundamental and Applied Aspects ofModern Physics,Laderitz, South Africa, 13:17.11 .200020.80 .0

IKP-00-21-041Kubis B .Low EnergyAnalysis of the Nucleon Electromagnetic Form FactorsInternational Conference on "Conference Chiral Dynamics: Theoryand Experiment", Newport News, USA, 17:22.7.200020.80.0

IKP-00-21-042Lieder R.M .Overview of Present and Future Gamma-Ray DetectorsWorkshop unter the EUTMR Tracking Project, Data AnalysisSchool, Niels Bohr Institute, Copenhagen, Denmark, 16.10.200020.10 .0

IKP-00-21-043Lieder R.M.Development of y-Ray Tracking DetectorsEURISOL Town Meeting, Orsay, France, 7.11 .200020.10.0

IKP-00-21-044Lieder R.M.Entwicklung von Gamma-Tracking DetektorenUniversität Bonn, Germany, 16.11 .200020.10 .0

IKP-00-21-045Machner H .Meson Production in p+d ReactionsXVII European Few Body Conf., Evora, Portugal,11:16.3.200020.45 .0

IKP-00-21-046Machner H .Meson Production in p+d ReactionsLaderitz 2000: Fundamental and Applied Aspects in ModernPhysics, Laderitz, South Africa, 13.-17 .11 . 200020.45 .0

IKP-00-21-047Machner H.Meson Production in p+d ReactionsInternational Symposium on Nuclear Physics, Mumbai, India,18:22.12.200020.45.0

IKP-00-21-048Magiera A. (for the GEM-Kollaboration)Reaction Mechanisms and Isospin Symmetry breaking in thepd43He7MHen Reactions9th Int. Conference on "Nucear Reaction Mechanisms, Varenna,Italy, 5:9.6.200020.45.0

IKP-00-21-049Meißner Ulf-G .Chiral Nucleon DynamicsGerman-Taiwanese Symposium on "The Structure of the Nucleon",Taipeh, Taiwan, 3.-6 .4.200020.80 .0

IKP-00-21-050Meißner Ulf-G .The Nucleon-Nucleon Interaction from Effective Field TheoryXVlth International Conference on "Few-Body Problems in Physics",Taipeh, Taiwan, 6.-10.3 . 200020.80 .0

IKP-00-21-051Meißner Ulf-G .The Spin Polarizabilities ofthe Nucleon and Related AspectsInternational Conference "GDH2000", Mainz, Germany,14:17.6.200020.80 .0

IKP-00-21-052Meißner Ulf-G .Goldstone Boson-Nucleon Dynamics : Theory SummaryInternational Conference on "Conference Chiral Dynamics: Theoryand Experiment", Newport News, USA, 17.22.7.200020.80 .0

IKP-00-21-053Meißner Ulf-G .2N, 3N and 4N Systems from a Chiral Effective Field TheoryInternational Conference on "Conference Chiral Dynamics : Theoryand Experiment", Newport News, USA, 17.-22 .7.200020.80 .0

IKP-00-21-054Meißner Ulf-G .Low Energy Analysis of the Nucleon Electromagnetic Form FactorsGordon Research Conference on "Photonuclear Physics", Tilton,USA, July 200020.80 .0

IKP-00-21-055Meißner Ulf-G .Chiral Dynamics with Strange QuarksLectures delivered at the "17th Students' Workshop onElectromagnetic Interactions", Bosen, Germany, 3:8.9.200020.80 .0

IKP-00-21-056Mihailescu L.Principles and Methods for Gamma-Ray Tracking with LargeVolume Ge DetectorsUniversität Bonn, Germany, 20.11 .200020.10.0

IKP-00-21-057Nikolaev N.N .Small-x Structure Functions and QCD PomeronInternational Workshop QCD-2000, Villefranche-sur-Mer, France,January 200020.80.0

IKP-00-21-058Nikolaev N.N .Anatomy of the BFKL Gluon Distributions at Small xInternational Workshop "Evolution Equations and Lightcone QCD",Gatchina, Russia, April 200020.80 .0

IKP-00-21-059Nikolaev N.N .Diffractive Vector Mesons in DIS : Meson Structure and QCDVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19.-23 .5.200020.80.0

IKP-00-21-060Nikolaev N.N .Helicity Properties of Deep Inelastic Scattering at Small xAnnual Conference Landau Days-2000, Moscow, Russia, June200020.80.0

IKP-00-21-061Nikolaev N.N .Color TransparencyInternational Workshop Diffraction-2000, Cetaro, Italy, September200020.80 .0

IKP-00-21-062Nikolaev N.N .Diffraction Cone in QCD: To Shrink or not to Shrink?2nd THERA-Meeting, DESY, Hamburg, Germany, 14.4.200020.80 .0

IKP-00-21-063Nikolaev N.N .Spin Dependence of Diffractive DISWorkshop "Spin in DIS", Dubna, Russia,December 200020.80 .0

IKP-00-21-064Oller J.A.Scalar Mesons and Chiral SymmetryYITP Workshop on "Possible Existence of the Sigma Meson and it

Implications to Hadron Physics (sigma-meson 2000)", Kyoto,

Japan, 12.-14 .6.200020.80 .0

IKP-00-21-065Oller J.A.Chiral Unitary Approach to Pion-Nucleon ScatteringInternational Conference on "Conference Chiral Dynamics : Theory

and Experiment", Newport News, USA, 17.-22 .7.200020.80 .0

IKP-00-21-066SchäferW.Diffractive Structure Function at Very Small Beta and Unitary

Corrections In the Colour Dipole Approach

e° International Workshop on Deep Inelastic Scattering and QCD-DIS2000", Liverpool, United Kingdom, 25:30.4.200020.80 .0

IKP-00-21-067Schnase,A .Cavities with a swing, Lecture given at 9th May at CERNAccelerator School, RF Engineering for particle accelerators,Lufthansa Training Center, Seeheim, 8-16 May 200020.30 .0

IKP-00-21-068Schnase, A.Harware R&D (conventional rf) and Applications :Signal synthesis, synthesizer Hardware, Board-Level Design, Chip-Design3-rd FFAG 2000 Workshop, 12.10.00 Tsukuba, Japan20.30.0

IKP-00-21-069Speth J .Effects of Channel Coupling in Hadron SpectroscoyIntern. Conference "Quark-Nuclear-Physics (QNP), Adelaide,Australia, 23.2.200020.80 .0

IKP-00-21-070Speth J.See-Quark Verteilungen im ProtonUniversität Dortmund, Germany, 30.5.200020.80 .0

IKP-00-21-071Speth J .Pions in Hadron PhysicsVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19:23.5.200020.80 .0

IKP-00-21-072Speth J.Scientific Approach to Stock Market DynamicsWestdeutsche Landesbank Luxembourg, Luxembourg, 6.11 .200020.80 .0

IKP-00-21-073Ströher, H .Experiments on the Nucleon with Real PhotonsKolloquium PSI (Schweiz), 21 January 200020.45.0

IKP-00-21-074Ströher, H .Hadron Physics with Cooled Proton BeamsKolloquium TU München, 15 February 200020.45 .0

IKP-00-21-075Ströher, H.Threshold Meson Production with Electromagnetic and HadronicProbesInt . Conf. on "Quark Nuclear Physics", Adelaide (Australia),

22 February 200020.45 .0

IKP-00-21-076Ströher, H .Strangeness Production with Strong ProbesWorkshop on �Open Strangeness at MAMI C", Mainz,

16 March 200020.50 .0

IKP-00-21-077Ströher, H .Measurement of Neutral Decays of N*'s at COSY

Workshop on "Baryon Excitations", Jülich, 2 May 2000

20.45 .0

IKP-00-21-078Ströher, H .Meson Production with Various ProbesWorkshop �MESON 2000", Cracow (Poland), 23 May 200020.45.0

IKP-00-21-079Ströher, H .Meson Photoproduction with TAPS at MAMIIX Seminar �Electromagnetic Interactions of Nuclei at Low andMedium Energies, Moscow, Russia, 21 Sept. 200020.50 .0

IKP-00-21-080Ströher, H .Connecting AGOR and COSY PhysicsAGOR Users Meeting, Groningen, The Netherlands, 9 Nov. 200020.45.0

IKP-00-21-081Ströher, H .Hadron Physics with Electromagnetic and Hadronic Probese Nat . Symp . On "Frontiers in Physics", Lahore, Pakistan,21 Nov. 200020.45 .0

IKP-00-21-082Tietze, A . ; Neef, R.-D . ; Filges, D. ; Goldenbaum, F.; Nünighoff, K. ;Paul, N .; Pohl, Ch . ; Schaal, H . ; Sterzenbach, G . :MC-Simulation of Spallation Induced Reactions on Lead andMercury Targets up to 24 GeVMC2000, Int. Conf. on Advanced Monte Carlo for RadiationPhysics, Particle Transport Simulation and Applications, Lissabon,Portugal, Oct. 23-26, 200020.90 .0

IKP-00-21-083Tietze-Jaensch, H . ; Conrad, H . ; Dietrich, J .; Filges, D. ; Haft, B . ;Hansen, G. ; Maier, R . ; Paul, N . ; Pohl, C. ; Prasuhn, D. ; Smimov, A. ;Stelzer, K . ; Ullmaier, H . and the international JESSICACollaboration :JESSICA, the ESS-like Target/Reflector Mock-Up and ColdModerator Test Facility[CANS-XV, 15'° Meeting of the Int. Collaboration on AdvancedNeutron Sources, Tsukuba, Japan, Nov. 6-9, 200020.90 .0

IKP-00-21-084Wirzba A.Cooper-Mesons in the Color-Flavor-Locked Superconducting Phaseof Dense QCDWorkshop "Structure of the Nucleus at the Dawn of the Century,Bologna, Italy, 29.5 .-3.6.200020.80 .0

IKP-00-21-085Zychor, I . for the ANKE collaborationStudy of Medium Modifications with the New Spectrometer ANKE atCOSY-JGlichProc . XXVIth Mazurian Lakes School of Physics, Sept, 1 - 11,1999, Krzyze, Poland, Acta Phys . Polonica B, 31, (2000) 35720,45.0

Conference Contributions

IKP-00-22-001Baru VFSI Effects in Meson Production in NN-CollisionsVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19:23.5.200020.80 .0

IKP-00-22-002Baur G .Indirekte Methoden in der nuklearen Astrophysik: Coulombaufbruchund Trojan-Horse-MethodeDPG Frühjahrstagung, Dresden, Germany, 20.-24.3.200020.80 .0

IKP-00-22-003Baur G .Wechselwirkung von Pionium mit MaterieDPG Frühjahrstagung, Dresden, Germany, 20.-24 .3.200020.80.0

IKP-00-22-004Baur G .Elektromagnetische Produktion von e+e-Paaren in peripherenStössen von SchwerionenDPG Frühjahrstagung, Dresden, Germany, 20.24.3.200020.80.0

IKP-00-22-005Baur G .Elektromagnetische Wechselwirkungen in hochenergetischen Kern-Kem-Stößen : von RHIC über LHC zur kosmischen StrahlungForschungszentrum Karlsruhe, Germany, 15.3.200020.80 .0

IKP-00-22-006Baur G .Astrophysical Reaction Cross-Sections and Problems with IndirectMethods RevisitedUniversity ofCatania, Italy, 12 .5.200020.80 .0

IKP-00-22-007Baur G.Photon-Hadron-Physik an relativistischen Hadron-CollidemCANU-Meeting, Bad Honnef, Germany, 18.-19 .12.200020.80.0

IKP-00-22-008Bongardt, K .Design Considerations and Beam Dynamics Results for an ESSLinacESS Accelerator R&D Meeting,Conseners House, Abington, 14.11 .0020.91 .0

IKP-00-22-009Bräutigam, W.F+E Arbeiten zur Entwicklung supraleitenderBeschleunigerkomponenten für den ESS-LinacESS-Treffen, Simonskall, 17.-18.04.0020.91 .0

IKP-00-22-010Bräutigam, W.Experimental Results with the SC Test ModuleESS Accelerator R&D Meeting,Conseners House, Abington, 14.11 .0020.91 .0

IKP-00-22-011Büscher, M .Measurement of Subthreshold K`-Production in pA Collisions withANKE,Workshop MESON 2000, Cracow, Poland, 19 - 23 May 200020.45.0IKP-00-22-012Büscher, M,Status of ANKE and Planned Measurements on pp -> dap,

Workshop on a 0 Physics with ANKE, Moscow, Russia,13-14 July 200020.45 .0

IKP-00-22-013Büscher, M .K`-Produktion in Proton-Kern-Stößen mit ANKE18. CANU Arbeitstreffen, 18 -19 December 2000,Bad Honnef20.45.0

IKP-00-22-014Dietrich, J .Kicker-Extraktion an COSYWinterseminar des Institutes für Angewandte Physik derJWGoethe-Universität Frankfurt/Main,27.2.-4.3.2000, Riezlern20.30 .0

IKP-00-22-015Elster Ch.Few-Body Calculations - An Approach without Partial WavesDPG Frühjahrstagung, Dresden, Germany, 20:24.3.200020.80 .0

IKP-00-22-016Elster Ch.Nucleon-Nucleon Scattering in a Three-Dimensional ApproachXVII European Conference on "Few-Body Problems in Physics",Evora, Portugal, 11 :16.9.200020.80 .0

IKP-00-22-017Elster Ch .Faddeev Calculations without Partial Wave DecompositionUniversity of Lissabon, Portugal, January 200020.80.0

IKP-00-22-018Elster Ch .Faddeev Calculations without Partial Wave Decomposition atHigher EnergiesUniversity of Bonn, Germany, February 200020.80 .0

IKP-00-22-019Elster Ch .Towards Faddeev Calculations at Intermediate EnergiesGSI Darmstadt, Germany, June 200020.80 .0

IKP-00-22-020Felden, O .Das AtomstrahltargetEDDA-Kollabortationstreffen,Hamburg, 13.-14 .09.0020.35 .0

IKP-00-22-021Felden, O.Commissioning of a superconducting accelerating structure

ESS-Treffen, Simonskall, 17.-18 .04.0020.91 .0

IKP-00-22-022Fettes N .Pion-Nucleon Scattering in Chiral Perturbation TheoryCALTECH, Kellogg Radiation Laboratory, Pasadena, USA,25.2.2000University of Washington, Seattle, USA, 12.4.200020.80 .0

IKP-00-22-023Gasparian A .A and E Production in pp-collisions near threshold171h Students Workshop on Electromagnetic InteractionsBosen, Germany, 1-8.9.200020.80.0

IKP-00-22-024GastW.High-Sin Isomers in Neutron-rich Yb IsotopesWorkshop "Physics with EUROBALL Detectors at GSI"Darmstadt, Germany, 23.11 .200020.10 .0

IKP-00-22-025GastW.Gamma-Ray Tracking - A new Detector Concept for NuclearSpectroscopyNato Advanced Study Institute, "Nuclei far from Stability andAstrohysics, Predeal, Romania, 7 .9.200020.10 .0

IKP-00-22-026Gebel, R.Status der polarisierten Quelle an COSYEDDA-Kollabodationstreffen,Hamburg, 13.-14.09.0020.35.0

IKP-00-22-027Gebel, R.Der polarisierte COSY-StrahlCANU ArbeitstreffenBad Honnef, 18-19.12 .0020.38.0

IKP-00-22-028Gillitzer A.N' Excitations in p-a ScatteringCOSY-Workshop "Baryons Exitations", Forschungszentrum J01ich,Germany, 2:3.5.200020.45 .0

IKP-00-22-029Gillitzer A .Deeply Bound Picnic States in PbWorkshop "MESON2000", Krakow, Poland, 19:23.5.200020.45.0

IKP-00-22-030Goldenbaum, F :Presentation of the European Spallation Source project.Conference on Research Infrastructures Palais des Congres et dela Musique of Strasbourg, Strasbourg, France, Sept . 18:20., 200020.90 .0

IKP-00-22-031Goldenbaum, F. for the NESSI-Collaboration :Die Prüfung von Simulationsprogrammen anhand von NESSI-Daten

18. CANU-Arbeitstreffen (COSY-Arbeitsgemeinschaft Nordrhein-Westfälischer Universitäten), Physikzentrum Bad Honnef, Dez. 18 .-

19,200020.48.0

IKP-00-22-032Gotta, D .Precision Measurement of the Charged Pion Mass . Outlook to the

Pionic Hydrogen ExperimentStatus report PSI experiments R-97.02 and R-98.01

PSI, Villigen, Schweiz, 26 June 200020.50 .0

IKP-00-22-033Gotta, D.Protonium X-ray SpectroscopyASACUSA collaboration meeting, 28 - 29 Nov. 2000, CERN, Genf,

Schweiz20.50.0

IKP-00-22-034Haidenbauer J .NearThreshold A und to Production in

PpCollisions

3' d Chinese-German Symposium on Medium Energy Physics,

Taipeh, Taiwan, 3-6.3.2000XVlth International Conference on Few-Body Problems in Physics,

Taipeh, Taiwan, 6.10 .3 .200020.80 .0

IKP-00-22-035Haidenbauer J .Mesonproduktion in Nukleon-Nukleon KollisionenDPG Frühjahrstagung, Dresden, Germany, 20.24.3.200020.80.0

IKP-00-22-036Haidenbauer J .The Reactions pn->dco and pn-+d~ and the Role of the OZI RuleXVII European Conference on Few-Body Problems in Physics,Evora, Portugal, 11 .-16 .9.200020.80 .0

IKP-00-22-037Hejny, V.Ein Photonendetektor für COSY18 . CANU Arbeitstreffen, 18 -19 December 2000,Bad Honnef20.45 .0

IKP-00-22-038Hennebach, M.Mass of the Charged PionMESON 2000, Krakau20.50 .0

IKP-00-22-039Herbach, C.-M . ; Filges, D .; Enke, M . ; Galin, J . ; Goldenbaum, F. ;Hilscher, D . ; Jahnke, U . ; Letoumeau, A . ; Loft, B. ; Neef, R.-D.;Nünighoff, K. ; Paul, N . ; Pdghaire, A. ; Pienkowski, L . ; Pohl, C.;Schaal, H . ; Schr6der, U . ; Sterzenbach, G . ; Tietze, A. ; Tishchenko,V. ; Toke, J . ; Wohlmuther, M . :p(GeV)+A-Spallation Reactions in Experiment and Simulation andNeutron Production by 0.4-2.5 GeV Proton Beams on Thick W, Hgand Pb Targets64. Physikertagung Dresden, Verhandl. DPG (VI) 35, 239 (2000),Dresden, März 20-24 ., 200020.90 .0

IKP-00-22-040Hesselbarth D .A-Produktion an TOFCANU-Meeting, Bad Honnef, Germany, 18-19.12.200020.45.0

IKP-00-22-041Kamerdzhiev S .News on Pairing Phenomena in Nuclear SystemsIPPE Obninsk, Russia, 11 .4.200020.80 .0

IKP-00-22-042Kamerdzhiev S .On Superfluidity ofAtomic NucleiIPPE Obninsk, Russia, 20.4.200020.80 .0

IKP-00-22-043Kamerdzhiev S .Some newAspects of Superfluidity in Finite Fermi SystemsINP Orsay, France, 8.11 .200020.80 .0

IKP-00-22-044Kamerdzhiev S .Some new Aspects of Superfluidity in Fermi SystemsUniversity of Rostock, Germany, 14.11.200020.80.0

IKP-00-22-045Khoukaz A. (for the COSY-11 Collaboration)Near Threshold Heavy Meson Production in pp- and pd-Collisionsat the Experiment COSY-11International Workshop XXVIII on Gross Properties of Nuclei andNuclear Excitations, Hirschegg, Austria, 16-22 .1.200020.50.0

IKP-00-22-046KhoukazA . (for the COSY-11 Collaboration)Schwellennahe Mesonenproduktion an COSY-11DPG-Frühjahrstagung, Dresden, Germany, 20.-24 .3.2000,20.50.0

IKP-00-22-047Kilian, K.New Experimental Results from COSYInt . Conf. on Quark Nuclear Physics, Adelaide/Australia,21 .-25 .2.200020.45 .0

IKP-00-22-048Kilian K .Study of Hyperon Resonances with TOFCOSY-Workshop "Baryons Exitations", Forschungszentrum Jülich,Germany, 2-3.5.200020.45.0

IKP-00-22-049Klimala W.Meson Production in p+d ReactionsDPG Frühjahrstagung, Dresden, Germany, 20.-24 .3.200020.45 .0

IKP-00-22-050Krewald S .What is the Structure of the Roper Resonance?The George Washington University, Washington, USA, 11 .2.200020.80 .0

IKP-00-22-051Krewald S .The GAMS-BNL Puzzle16`" IUPAP International Conference on "Few-Body Problems inPhysics", Taipei, Taiwan, 6.-10 .3.200020.80 .0

IKP-00-22-052Kubis B.Hgeron Form Factors in Chiral Perturbation Theory17 Students Workshop on Electromagnetic InteractionsBosen, Germany, 3-8.9.200020.80 .0

IKP-00-22-053Lieder R.M.The TMR network project "Development of Gamma-Ray TrackingDetectors"DPG Frühjahrstagung, Dresden, Germany, 20-24.3.200020.10.0

IKP-00-22-054Lieder R.M .Study of Quadrupole Moments of Superdeformed Bands in 145GDDPG Frühjahrstagung, Dresden, Germany, 20.-24.3.200020.10.0

IKP-00-22-055Lieder R.M .Introduction ofthe y-Ray Tracking Detector ProjectTMR User Meeting on "Gamma-Ray Tracking Detectors", K61n,Germany, 13.6.200020.10 .0

IKP-00-22-056Lieder R.M .The TMR network project "Development of Gamma-Ray TrackingDetectors"Int . Conf. on "Nuclear Structure 2000", East Lansing, USA,17.8.200020.10.0

IKP-00-22-057Lorentz, B .Kernpolarisation von Wasserstoff- und Deuterium-MolekülenCANU ArbeitstreffenBad Honnef, 18-19.12 .0020.35 .0

IKP-00-22-058Machner H .Introduction to BIG KARL Physics-BrainstormingPhysics with BIG KARL, Forschungszentrum Jülich, Germany, 10 .-12.4.200020.45 .0

IKP-00-22-059Martin, S.Anmerkungen zur physikalisch /technischen Auslegung desHochenergieteils eines SC-Linac'sESS-Treffen, Simonskall, 17.-18 .04.0020.91 .0

IKP-00-22-060Martin, S.SC-Linac Costing MethodsESS Accelerator R&D Meeting,Conseners House, Abington, 14.11 .0020.91 .0

IKP-00-22-061Marwinski S .Erste Resultate zur il-Produktion an TOFCANU-Meeting, Bad Honnef, Germany, 18.19.12.200020.45.0

IKP-00-22-062Mihailescu L .Decomposition of Multiple Interactions based on Wavelet TransformTMR User Meeting on "Gamma-Ray Tracking Detectors", Kö1n,Germany, 13.6.200020.10 .0

IKP-00-22-063Mihailescu, L .Gamma-Ray Imaging with Large Volume Ge Detectors2nd International Workshop on "Radiation Imaging Detectors",Freiburg, Germany, 3.7.200020.10 .0

IKP-00-22-064Morsch H.-P.Structure of the P11(1440 MeV)ScatteringCOSY-Workshop "Baryons Exitations", Forschungszentrum J011ch,Germany, 2.-3 .5.200020.45 .0

IKP-00-22-066Oelert W.Antimaterie - Physik im SpiegelbildUniversität Köln, Germany, 25.01 .200020.50 .0

IKP-00-22-067OelertW.Antimaterie - Physik im SpiegelbildUniversität Tübingen, Germany, 9.2.200020.50 .0

Resonance from a-p and 7r-N-

IKP-00-22-065Morsch H . -P.What is the Structure of N" Resonances?CANU-Meeting, Bad Honnef, Germany, 18:19.12.200020.45.0

IKP-00-22-068Oelert W.Materie und MarylinTheresien-Gymnasium Ansbach, Forschungszentrum Jülich,Germany, 15.3.200020.50 .0

IKP-00-22-069Oelert W.Antimaterie - Die gespiegelte Materie als Antrieb zurGrundlagenforschungReise zum Urknall, Physik 2000, Urania, Berlin, Germany, 7.4.200020.50 .0

IKP-00-22-070OelertW.Antimaterie - Ein Antrieb zur Grundlagenforschung Ringvorlesung;

Wasserstoff Saturday morning physicsRuhr-Universität Bochum, Germany, 29.4.200020.50.0

IKP-00-22-071OelertW.Antimaterie - Die gespiegelte Materie als Antrieb zurGrundlagenforschung2000 - Das Jahr der Physik, Die Reise zum Urknall,DESY-Hamburg EXPO-2000, Germany, 8.6.200020.50 .0

IKP-00-22-072OelertW.Associated Strangeness Production at COSY-11Oberjoch-Meeting, Universität Tübingen, Germany, 7.9.200020.50 .0

IKP-00-22-073Oelert W.Materie aus AntimaterieDie Erzeugung von AntiwasserstoffatomenURANIA-Reihe 100 Jahre Quantentheorie, 17.10.200020.50 .0

IKP-00-22-074Oelert WAntimaterie - Materie aus AntiteilchenUniversität Stuttgart, Germany, 5.12.200020.50 .0

IKP-00-22-075Prasuhn, D .COSY: Status und ZukunftCANU ArbeitstreffenBad Honnef, 18-19.12 .0030.30.0

IKP-00-22-076Roderburg E .Measurement of the 11-Production in Proton-Proton Collisions withthe COSY-TOF-SpectrometerWorkshop "MESON 2000", Krakow, Poland, 19:23.5.200020.45 .0

IKP-00-22-077Roderburg E .Physik mit dem Flugzeitspektrometer an COSYUniversität Bonn, Germany, 25.5.200020.45.0

IKP-00-22-078Schäfer W.Diffractive Structure Function at Very Small Beta2"° THERA-Meeting, DESY, Hamburg, Gennany, 14.4.200020.80 .0

IKP-00-22-079SchaferW.Inclusive Production of Forward Neutrons and the Pionic Content ofthe NucleonVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19.-23 .5.200020.80 .0

IKP-00-22-080Schleichert, R .Vertex-Rekonstruktion und Spektator-Detektion an ANKE18 . CANU Arbeitstreffen, 18 -19 December 2000,Bad Honnef20.45 .0

IKP-00-22-081Schnase, A .Pulsed Mode Operation of a Superconducting CavityESS-Treffen, Simonskall 17 .04 .00,20.91 .0

IKP-00-22-082Schneider S .The Reaction 1N->nnN in the Framework of a Meson Exchange

ModelVI International Workshop on Production, Properties and Interaction

of Mesons "MESON2000", Krakow, Poland,

19:23.5.200020.80 .0

IKP-00-22-083Schneider S .Zwei-Pionenproduktion in hadronischen Prozessen am NukleonCANU-Meeting, Bad Honnef, Germany, 18.19.12.200020.80 .0

IKP-00-22-084Schwiete G .Higher Order Coulomb Corrections to the Primakoff Measurementof the n° LifetimeVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19.-23.5.200020.80 .0

IKP-00-22-085Stassen, R.Aufbau des HF-Testsystems und erste Messungen am SC-TestmodulESS-Treffen, Simonskall, 17.18.04.0020.91 .0

IKP-00-22-086Stassen, R.FZ-Jülich activitiesWorkshop on R&D on Superconducting Proton Linac, Saclay,Frankreich20.91 .0

IKP-00-22-087Quentmeier C. (for the COSY-11 Collaboration)Untersuchung der Reaktion pp->ppK+K- nahe derProduktionsschwelle am Experimentaufbau COSY-11DPG Frhhjahrstagung, Dresden, Germany, 20.-24 .3.200020.50.0

IKP-00-22-088Walzl M.Isospin Violation in the Two-Nucleon SystemVI International Workshop on Production, Properties and Interactionof Mesons "MESON2000", Krakow, Poland,19.23 .5.200020.80.0

IKP-00-22-089Walzt M .Ein effektives Nukleon-Nukleon Potential in chiraler FeldtheorieCANU-Meeting, Bad Honnef, Germany, 18.19.12.200020.80 .0

IKP-00-22-090Wintz FStatus of Muon Electron Conversion at PSIWorkshop on "New Initiatives in Lepton Flavor Violation andNeutrino Oscillations with Very Intense Muon and NeutrinoSources"University of Hawaii, USA, 2.-6.10.200020.45 .0

IKP-00-22-091Wolke M. (forthe COSY-11 Collaboration)Hyperon Production at the COSY-11 FacilityInternational Workshop XXVIII on Gross Properties of Nuclei andNuclear Excitations, Hirschegg, Austria, 16:22 .1 .200020.50 .0

IKP-00-22-092Wolke M . (for the COSY-11 Collaboration)Exclusive Strangeness Production in Proton-Proton Scattering atCOSY17 . Students' Workshop on Electromagnetic Interactions,Sonderforschungsbereich 443 Vielkörperstruktur starkwechselwirkender Systeme' der DeutschenForschungsgemeinschaft (DFG), Bosen (Saar), Germany,September 200020.50.0

IKP-00-22-093Wolke, MagnusHyperon Production at the COSY-11 FacilityInt. Workshop XXVIII on Gross Properties of Nuclei and NuclearExcitations, Hirschegg 2000 : Hadrons in Dense Matter, Hirschegg,16:22.1 .199920.50 .0

IKP-00-22-0941Wolke, MagnusExclusive strangeness production in proton-proton scattering atCOSYStudents' Workshop on Electromagnetic Interaction, Bosen (Saar),3:8.9.200020.50.0

IKP-00-22-095Zaplatin, E .Superconducting Accelerating StructuresESS-Treffen, Simonskall, 17:18.04.0020.91 .0

Poster

IKP-00-23-001Ackens, A ., Clemens, U., Gorke, H., Gotta, D ., Holl, P.,Loevenich, H ., Maeckelburg, D ., Ramm, M., Strüder, L .,von Zanthier, C ., Simons, L . M., Zwoll, K .A high-rate X-ray detector for exotic-atom spectroscopyDPG Spring meeting, Dresden, 20 - 24 March 200020.50.0

IKP-00-23-002Anagnostopoulos, D, Augsburger, M., Borchert, G ., Chatellard, D.,EI-Khoury P, Egger, J.-P, Gotta, D ., Hauser, P, Hennebach, M.,Engels, R., Emmerich, R ., Ley, J . and Paetz gen . Schieck, H . fürdie ANKE-KollaborationAufbau und erste Tests eines Lambshiftpolarimeters für daspolarisierte Target an ANKE/COSYDPG Spring meeting, Dresden, 20 - 24 March 200020.50.0

IKP-00-23-003Bräutigam, W., Brings, R . ; Gebel, R.; Rindfleisch, U .Recent Investigations at the COSY Injector CyclotronECPM XXXII, Berlin 20:23.9.200020.30 .0

IKP-00-23-004Dietrich, J. ; Bojowald, J . ; Labus, H ., Lawin, H . ; Mohos, I .Beam Instrumentation for fast Kicker Extraktion at COSY-JOlich9th Beam Instrumentation Workshop, Boston, May 8-11, 200020.35 .0

IKP-00-23-005Eller, R.,

Hennebach, M .

and

Koch, H. R .

for

the

ANKEcollaborationKaon-pion separation at ANKE with differential Cherenkov detectorsDPG Spring meeting, Dresden, 20 - 24 March 200020.45 .0

IKP-00-23-006Gast W., Lieder R.M., Mihailescu L., Rossewij M.J .Digital Signal Processing for y-Ray Tracking based on PPADCHardwareDPG Frühjahrstagung, Dresden, Germany, 20.-24 .3.200020.10 .0

IKP-00-23-007Gast W., Lieder R.M ., Mihallescu L., Rossewij M.J ., Brands H .,Georgiev A ., Stein J ., Kr6ll Th .Digital Signal Processing and Algorithms for Gamm-Ray TrackingIEEE Nuclear Science Symp. and Medical Imaging Conf., Lyon,France, 17.10.200020.10 .0

IKP-00-23-008Hartmann, M., Drochner, M., Erven, W., Watzlawik, K.H.,Wuestner, P and Zwoll, K . for the ANKE collaborationThe ANKE Data Acquisition SystemDPG Spring meeting, Dresden, 20 - 24 March 200020.45.0

IKP-00-23-009Indelicato, P., Kirch, K ., Lenz, S ., Liu, Y-W, Manil, B ., Nelms, N .,Siams, Th ., and Simons, L . M .Charged Pion Mass Determination and Energy-CalibrationStandards based on Plonic X-ray TransitionsHydrogen Atom II : Precise physics of simple atomic systems (PSAS2000)Castiglione della Pescala, Italy, 1" - 3`° June 200020.45.0

IKP-00-23-010Junghans, H . for the ANKE collaborationDetermination of double differential cross sections for subthresholdK+ production at ANKEDPG Spring meeting, Dresden, 20 - 24 March 200020.45 .0

IKP-00-23-011Lehmann, I ., Barsov, S ., Dewald, A., Merzliakov, S ., Mussgiller, A .,Protic, D ., Schleichert, R . and Steinart, C. for the ANKEcollaboration

Silicon Detectors for low energetical Spectator-Proton andLuminosity Measurements at ANKEDPG Spring meeting, Dresden, 20 - 24 March 200020.45 .0

IKP-00-23-012Lieder R.M ., Rzaca-Urban T, Brands H ., Gast W, Jäger H.M .,Mihailescu L., Pytel Z ., Urban W., Morek T, Droste Chr., Chmel S .,Bazzacco D., Falconi G ., Menegazzo R., Lunardi S ., Ross! AlvarezC., de Angelis, G ., Famea E., Gadea A ., Napoli D.R ., Podolyak Z.Study of Oblate Dipole and Triaxial Quadrupole Bands in ' 4 Gd withEUROBALLDPG Frühjahrstagung, Dresden, Germany, 20:24.3.200020.10.0

IKP-00-23-013Lieder R.M., Rzaca-Urban T, Brands H ., Gast W, Jäger H.M.,Mihailescu L ., Pytel Z., Urban W., Morek T, Droste Chr. ; Chmel S.,Bazzacco D ., Falconi G ., Menegazzo R., Lunardi S., Rossi AlvareiC., de Angelis, G., Famea E ., Gadea A ., Napoli D.R., Podolyak Z .Investigation of Magnetic Rotation in 142Gd with EUROBALLInt. Conference on Nuclear Structure 2000, East Lansing, USA,16.8.200020.10 .0

IKP-00-23-014Mihailescu L ., GastW., Lieder R.M ., Rossewij M.J .On-line Pulse Shape Analysis Algorithms fory-Ray TrackingDPG Frühjahrstagung, Dresden, Germany, 20.24.3.200020.10.0

IKP-00-23-015Mosbacher C.A .Study of AA Excitations in the Reaction n+p->d+nrcPosterbeitrag, Conference ,BARYONS98", Bonn, Germany, 22 .-26.9.199820.80.0

IKP-00-23-016Moskal P (for the COSY-11 Collaborationrl and il'-Meson Production at COSY-11DPG Frühjahrstagung, Dresden, Germany, 20.-24.3.2000Verhandlungen der DPG (VI) 36,229 (2000), HK 15.920.45 .0

IKP-00-23-017Mussgiller, A .,

Barsov, S ., Lehmann, 1 ., Merzliakov, S .,

Protic, D .and Schleichert, R . for the ANKE collaborationSelftriggering Frontend Chips for the ANKE Vertex DetectorDPG Spring meeting, Dresden, 20 - 24 March 200020.45.0

IKP-00-23-018Protic, D . ; Stöhlker, Th. ; Bayer, H.F ; Bojowald, J . ; Borchert, G . ;Gumberidze, A. ; Hamacher, A . ; Ma, X. ; Mohos, I . :A Micro-Strip Germanium Detector for Position Sensitive X-RaySpectroscopy2000 IEEE Nuclear Science Symposium and Medical ImagingConference, Lyon, France, Oct. 15-20, 200020.20 .0

IKP-00-23-019Schleichert, R.,

Barsov, S .,

Lehmann, I .,

Merzliakov, S .,Mussgiller, A. and Protic, D. for the ANKE collaborationDevelopment ofa Vertex Detector for the ANKE SpectrometerDPG Frühjahrstagung, Dresden, 20 - 24 March 200020.45.0

IKP-00-23-020Schneider, Ch ., Müller, H . für die ANKE-KollaborationVergleich erster Ergebnisse zur K' Messung an ANKE mitModellrechnungenDPG Frühjahrstagung, Dresden, 20 - 24 March 200020.45.0

Patents

IKP-00-31-001Bert M., Eberth J ., Jäger H.M ., Kämmerling H., Lieder R.M., RenftleW.Kapsel für einen im Ultrahochvakuum arbeitenden DetektorEuropäisches Patent Nr. 0710364, erteilt am 20.9.2000PT 1 .114920.10 .0

Application for Patents

IKP-00-32-001Labus H .Verfahren zur Ermittlung der absoluten Intensität hochenergetischerlonenstrahlungDE : 100 20 582.8-52 (28.04.2000)PT 1 .178704000319

Lectures at Universities

WS 199912000

IKP-00-4-001Filges, D.Seminar über Abschirmprobleme von TeilchenbeschleunigernUniversität Wuppertal, V21 .4 ESS

SS 00

IKP-00-4-002Baur G .Einführung in die allgemeine Relativitätstheorie und KosmologieUniversität Basel, Schweiz, V220.80.0

IKP-00-4-003Filges, D .KemphysikUniversität Wuppertal, V21 .1 KPH, 1.4 ESS

IKP-00-4-004Krewald S .Einführung in die Theorie der starken WechselwirkungUniversität Bonn, V220.80.0

IKP-00-4-005Machner, H .Kern- und ElementarteilchenphysikUniversität Essen, V51 .1 KPH

IKP-00-4-006Machner, H .Seminarzur Kein- und ElementarteilchenphysikUniversität Essen, S11 .1 KPH

IKP-00-4-007Maier, R .Teilchenbeschleuniger IIUniversität Bonn, V220.30 .0

IKP-00-4-008Meißner Ulf-G .Elektronenstreuung und die Struktur der HadronenUniversität Bonn, V228.80 .0

IKP-00-4-009Speth J .Elektronenstreuung und die Struktur der HadronenUniversität Bonn, V220.80 .0

IKP-00-4-010Ströher, H .Experimente zur Struktur des Nukleons (Spezialvorlesung)20.45 .0

WS 00101

IKP-00-4-011Baur G.Kosmologie und Allgemeine RelativitätstheorieUniversität Basel, Schweiz, V220.80 .0

IKP-00-4-012Filges, D .Physik II, Atom- und KernphysikUniversität Wuppertal, V2, 021 .1 KPH, 1 .4 ESS,

IKP-00-4-013Gillitzer A.Atomphysik/Atomic Physics (Physik 5)Universität Bonn, V2, 0120.45 .0

IKP-00-4-014Kilian, K.Atomphysik/Atomic Physics (Physik 5)Universität Bonn, V2, 0120.45 .0

IKP-00-4-015Krewald S .Klassische Mechanik und Elektrodynamik für LehramtsstudierendeUniversität Bonn, V4, 0220.80 .0

IKP-00-4-016Lieder R.M .Kernphysikalische Messmethoden in Wissenschaft und TechnikUniversität Bonn, V2, 0120.10 .0

IKP-00-4-017Maier, R .Anwendung von TeilchenbeschleunigernUniversität Bonn, V220.30 .0

IKP-00-4-018Meißner Ulf-G .Thermodynamik und StatistikUniversität Bonn, V4, 0420.80 .0

IKP-00-4-019Sistemich, K .Experimentalphysik 11 für Studierende der NaturwissenschaftenUniversität Köln, V420.45 .0

IKP-00-4-020Speth J .Thermodynamik und StatistikUniversität Bonn, V4, 0420.80 .0

IKP-00-4-021Wirzba A .Quantenfeldtheorie (Theoretisches Wahlfach)"Technische Universität Darmstadt, V2, 11120.80 .0

247

XI. INDEX OF AUTHORS

ATRAP-Collaboration 67, 68, 69COSY-11-Collaboration 44, 45, 46,

47, 48, 49,50, 51, 52

ANKE-Collaboration 15COSY-GEM-Collaboration 53, 54, 55,

56, 57, 157COSY-EDDA-Collaboration 59COSY-TOF-Collaboration 7, 8, 9,10, 11COSY-MOMO-Collaboration 157NESSI-Collaboration 167, 168,

169,170PISA-Collaboration 172,173TMR-Collaboration 75

Abdel-Bary, M. 13,14 Busch, M. 59Abdel-Samad, S. 13,14 Büttiker, P. 107Adam, H. H. 50 Caia, G. 99Altmeier, M. 59 Cargnelli, M. 71Anagnostopoulos, D. 71,72 Cassing, W. 38,39Ananthanarayan, B. 107 Chernetsky, V. 34

. Angelis, de G. 77 Chernyshev, V. .27, 29, 34Balanutsa, V. 34 Chumakov, M. 34Barsov, S. 25,26 Clement, H. 11Baru, V. 114 Colberg, T . 59Bauer, F. 59,146 Conin, L. 149Baur, G. 132, 133, 134, 135 Daemen, J . 11,Bazzacco, D. 77Bechstedt, U. 143,149

Dahl, C.Dahmen, B.

59153

Beck, R. 70 Deliege, C. 146,154Bednarczyk, P. 78

62Demir6rs, L.Derissen, W.

59153Bellemann, F .

Berchem, C. 203 Deutsch, C. 184

Berg, A. 62Bernard, V. 87, 88, 93

Dewald, A.Diehl, O.

7759

Bisplinghoff, J . 59, 62, 153 Dietrich, J .Dmitriev, A.

14334

Bohlscheid, G. 62B6ge, H . G. 148 D6ring, K. 70

149,203Böhnke, M. 148Bojowald, J . 68,203

Dolfus, N.Droste, C. 78

Bongardt, K. 192,195 Drozdz, S.Durso, J . W.

13699

Bongers, N. 146,154Borchert, G.L . 71,72 Dymov, S.N . 19, 22, 25

72Borgs, W. 34 Egger, J.-P .

Elster, C. 94, 97, 98, 99, 100,Boukharov, A. 34Bräutigam, W. 147, 177, 180, 182

Emmerich, R.11932,

186, 188, 19071 Enge, R. 149,153

Breunlich, W.147 Engel, J . 157

Brings, R.10 Engelhardt, H. P . 59

Brinkmann, K.T .Br6ke1, E. 203 Engels, R.

Enke, M.32,167, 168,169, 170

Büscher, M. 5, 16, 18, 19, 22, 27,29, 30, 34, 37, 39, 41, Epelbaum, E. 94, 95, 96

43 Erhardt, A. 1162

Büßer, K. 59 Ernst, J .Ernst, W. 203

Bulgac, A. 128

Erven, W. 68 Jarczyk, L. 62Etzkorn, F.-J . 146,148 Jensen, H. J . 77Eversheim, P.D. 59, 153 Jensen, T. 71Eyrich, W. 7 ' Johnen, U. 11Eyser, O. 59 Jonas, E. 59Faber, P. 149,153 Joosten, R. 62Fachruddin, I . 97,98 Junghans, H. 16Fedorets, P. 27,34 Kacharava, A. 22Felden, O. 59, 153, 161, 182 Kachzarowski, R. 78Fettes, N. 115, 116, 117 Kaiser, N. 87Filges, D. 11, 12, 167, 168, 169, Kamada, H. 94,96

170 Kamerdzhiev, S. 131Fiori, G. 204 Kämmerling, H. 11Fleischer, N. 11 Karsch, L. 10Freiesleben, H. 10 Kasemann, S. 77Fuhrmann, H. 71 Khoukaz, A. 20, 47, 49, 50Gad, N. 147,153 Kilian, K. 11,12,13,14Galin, J. 167, 168, 169, 170 Kirchbach, M. 127Gasparian, A. 113,114 Kisielinski, M. 78Gast, W. 77, 78, 79, 80, 82 Kitanina, E. 32Gebel, R. 59, 146, 147, 153 Kleber, V. 29Geck, I . 50 Klein, R. 11, 13, 14Gellas, G. C. 89 Kleines, H. 32Geyer, R. 12 Klehr, F. 32Giersch, M. 71 Klemt, V. 137Ginszburg, I . F . 124 Komarov, V.I . 19, 21, 22, 24, 36, 43Glende, M. 59, 153, 177, 180, 182 Kondratyuk, L. 29, 30, 37, 39, 41, 113G16ckle, W. 96, 97, 98 Koptev, V. 16, 19, 27, 32G6bbels, J. 161 Kordyasz, A. 78Goldenbaum, F. 167, 168, 169, 170 Kowalczik, M. 78Golubeva, Ye. S. 30,39 Kowina, P. 45,51Gorke, H. 68 Kownacki, J. 78Gotta, D. 71,72 Kozela, A. 62Greiff, J . 59 Kozlov, V. 12Grishina, V. 30, 37, 41 Krafft, K. 161Groß-Hardt, R. 59 Krause, H. 59Gruber, A. 71 Kravtsov, P. 32Grümmer, F. 136 Krebs, H. 88Grzonka, D. 45, 67, 68, 69 Krein, G. 110Hadamek, H. 11, 68, 147, 153 Kress, J . 11Hadjimichef, D. 110 Krewald, S. 108,118Haidenbauer, J . 99, 100, 110, 112, 113, Krings, T. 26,204

114 Krol, G. 149Halabuka, Z. 134 Kruck, K. 157Hanhart, Ch. 113 Kubis, B . 90,91Hansen, G. 11 Kudryavtsev, A. 109,114Heim, T.A. 135 Kuhhnann, E. 6Hejny, V. 35, 38, 39, 70 Kulikov, AN. 24Hemmert, T.R . 89,93 Kurbatov, A. 19,24Hencken, K. 132, 133, 134, 135 Labus, H. 203Hennebach, M. 71,72 Lang, N. 20Herbach, C. 167, 168, 169, 170 Langenberg, G. 149Hesselbarth, D. 8 Lehmann, C. 59Hilscher, D. 167, 168, 169, 170 Lehmann, I. 25,26Hinterberger, F . 59,62 Leim, C. 23Ibald, R. 62 Letchford, A. 192,195Indelicato, P. 71,72 Letourneau, A. 167, 168, 169, 170Ivanov, I. 123,124 Ley, J . 32Jach, K.D .Jäger, H.M.

14977

Lieder, R.M.Lindemann, T.

75, 77, 78, 79, 80, 8259Jahn, R. 62,157 Lindlein, J . 59Jahnke, U. 167, 168, 169, 170 Lister, Th. 50

Jamin, M . 104,106 Liu, Y. W. 71,72

249

Lorentz, B . 32, 59, 143, 146 Palomar, J. 103Lott, B . 167, 168, 169, 170 Papureanu, S . 148Lunardi, S. 77 Pasternak, A. 77,79Lürken, G. 203 Paul, N. 11, 167, 168, 169,170Macharashvili, G.G. 21,22 Pauly, C. 59Machner, H. 62,157 Pavan, P. 77Magiera, A. 62 P6ghaire, A. 167, 168,169,170Maier, R. 59, 143, 157, 177, 182 Petrache, C.M. 77

186,188 Petrus, A.Yu . 24Manil, B. 71,72 Pich, A. 104,106Marcinkowska, Z. 77 Pienkowski, L. 168, 169, 170Markushin, V. 71 Plettner, C. L . 10Martin, S . 177,180 Podsvirova, E. 0. 77,79Marton, J. 71 Prasuhn, D. 59,143Marwinski, S . 9 Probst, H.J . 161Maschuw, R. 59,62 Protic, D. 25, 26, 204Mayer-Kuckuk, T. 62 Pütz, H. 149Meczynski, W. 78 Quentmeier, C. 44, 47, 49Medina, N.H. 77 Rathmann, F. 32, 36, 43Meier, H. 134,182 Rejmund, M. 77Meinerzhagen, A. 59 Renftle, W. 11Meißner, U.-G. 87, 88, 89, 90, 91, Rho, M. 125

93, 95, 96, 101, 105, Rindfleisch, U. 32, 68, 147, 153, 157111,115,116,117 Roderburg, E. 11

Meixner, C. 11 R6mer, K. 35,70Menegazzo, R. 77 Rogozik, B . 149Menzel, S. 11 Rohdjeß, H. 59Mertler, G. 62 Rosendaal, D. 59, 62, 153Merzliakov, S . 25,26 Rossen, v. P . 59, 62, 146, 153, 157Metz, H. 204 Rossewij, M. J. 80Mihailescu, L. 80,82 Rossi-Alvarez, C. 77Mikirtichyants, M. 32 Rotert, N. 153Mohos, I . 12 Ruchowska, E. 78Morek, T. 78 Ruf, F. 136Moskal, P . 46, 48, 52 Ruhrig, D. 148,149Müller, A. 153 Rzaca-Urban, T. 77,78Müller, H. 18,31 Sagefka, Th. 149,153Munkel, J.Mussgiller, A.

6225,26

Sarkadi, J .Sassen, F .

32108

Nähle, 0. 59 Schaal, H. 167, 168, 169, 170

Nakayama, K. 112 Schäfer, W. 120,122149Napoli, D .R .

Napsuciales, M.77127

Scheiba, F .Schepers, G. 67, 68, 69

Neef, R.-D . 167, 168, 169, 17016, 19, 32

Schirm,N.Schleichert, R.

5922, 25, 26

Nekipelov, M.Nellen, R. 12, 68, 203 Schnase, A. 143, 146, 148, 182

Nelms, N. 71,72 Schneider, C.Schneider, H.

18143

Nelyubin, V.V .Nikolaev, N.N.

32120, 122, 123 Schneider, S. 118

62Nioradze, M.S . 22

96Schnitker, H.Schroeder, U. 168,170

Nogga, A.Novotny, R. 35,70 Schug, G. 177, 180, 182, 184

186,188Nowak, M. A.Nünighoff, K.

12612, 167, 168, 169, 170 Schulte-Wissermann M. 10

135Oelert, W. 67, 68, 69 Schumann, M.

Schwarz, V. 59Ohm, H.Oller, J.A .

24101, 103, 104, 105, Schwiete, G. 120

59106,111 Scobel, W.

Sefzick, T. 67, 68, 69Orfanitski . S . 12

103 Seyfarth, H. 32, 36, 43Oset, E.Pabst, M. 192,195 Shuryak, E.

Sibirtsev, A.12538, 100, 119

Paetz gen. Schieck, H. 32 Siemsaszko, M. 51Palacz, M. 78

Simon, M. 154Simons, L.M. 71,72Singer, H. 153, 182, 186, 186Sistemich, K. 16Smyrski, J . 62Speth, J. 108, 112, 113, 114,

118, 131, 136Srebrny, J . 78Starosta, K. 78Stassen, R. 143, 182, 184, 186,

188Stechemesser, H. 11Steffens, E. 32Sterzenbach, G. 167, 168, 169, 170Stockhorst, H. 143, 146, 148Str6her, H. 6, 19, 30, 37, 38, 39,

41,43Strzalkowski, A. 62Styczen, J . 78Tarasov, V. 109Tertychny, G. 131Tietze, A. 167Tishchenko, V. 168, 169, 170Tölle, R. 62, 143, 146, 154, 157Toke, J . 168,170Trautmann, D. 132, 133, 134, 135Trelle, H. J . 59Typel, S. 132Ulbrich, K. 59Urban, W. 77,78Utzelman, S . 77Uzikov, Yu. 19, 36, 43Vassiliev, A. 32Walzl, M. 95Weise, E. 59Wellinghausen, A. 59Wesolowski, E. 78Wiedner, C.-A . 177Wilkin, C. 19,62Wilms, A. 5Wintz, P. 12Wirzba, A. 125, 126, 127, 128Witala, H. 96Wohlmuther, M. 167Wolf, T. 59Wolter, H.H. 132Wüstner, P . 68Yaschenko, S .V. 19, 24, 43Zahed, 1 . 125,126Zalikhanov, B . 24Zaplatin, E. 184,190Zhu, L. 77Ziegler, R. 59Zmeskal, H. 71Zoller, V. R. 122Zwoll, K. 32,68Zychor,1 . 28