NSTAR2007@Bonn 9/8/07-1 Simon Capstick, Florida State University.

NSTAR2007@Bonn 9/8/07-1Simon Capstick, Florida State University


NSTAR 2007 Summary

• Experiment/analysis– Facilities/new results– Upcoming developments

• Theory– Baryons– Dynamics of reactions involving baryons


BRAG pre-meeting

• L. Tiator, A. Svarc; problem relating experimental results to theoretical predictions

– Partial wave analysis and amplitude analysis give reliable results for dressed scattering matrix singularities

– Quark model calculations give information on bare resonant quantities

• Does not apply to those states seen in chiral unitary models—see talks by A. Ramos, E. Oset, A. Martinez Torres, and M. Doering at this meeting

• Dressing (un-quenching) the quark model is tough, but solvable in principle

– See talks by E. Santopinto, R. Bijker, and B. Pasquini at this meeting; S.C. and M. Giannini in BRAG pre-meeting

• Undressing dressed scattering matrix singularities in coupled-channel models is in principle a model-dependent procedure because of presence of model-dependent hadronic mass shifts

– From unmeasurability of off-shell effects accompanying any dressing procedure.

– BRAG pre-meeting talks by Ch. Hanhart, S. Scherer, J. Gegelia


BRAG pre-meeting

Conclusions: (1) Bare quantities in coupled-channel models are

legitimate quantities to be extracted– Only within a framework of a well defined model– To interpret, keep track of the existence of the

hadronic mass shifts produced by off-shell-ambiguities

(2) Dressed scattering matrix singularities are best meeting point between quark model predictions and experiments

– Recommendation: put a lot of effort into defining and thoroughly checking the pole extraction procedures

• starting either from energy dependent partial waves or from partial wave data directly


Experimental programs for N*

• Common developments:– Precision data on host of final states

• Emphasis on N, N, 2N, N, K, K,…

– Polarization (beam, target, double planned or underway)

• Aim is to measure as many observables as possible for a subset of these reactions (“complete” experiments)

– Reduce (not eliminate) model dependence of analysis

• Challenge for models to fit polarization observables– Strong sensitivity to resonance properties

• This is how physics progresses!


CLAS@Jefferson Lab

• V. Burkert: CLAS collaboration – Major focus is N* physics

• the search for new baryon states and determination of baryon resonance properties

• resonance transition form factors

– Nucleon spin structure in the transition region

• polarized proton structure function g1(x,Q2)

• Bjorken Sum: 1p-n(Q2)

– Deeply exclusive processes and generalized parton distributions (GPDs)

• DVCS/Bethe-Heitler beam spin asymmetry sensitive to H

Expt.


CLAS@Jefferson LabExpt.

• Search for new baryon states– Aim for “complete” or nearly complete

measurements• γp→πN, ηN, K+Y and γn→πN, K0Y • Combinations of beam, target (new FROST target),

and recoil polarizations– differential cross sections with unpolarized, circularly

polarized, and linearly polarized photon beams– recoil polarizations for hyperons– longitudinally or transversely polarized proton and

neutron (deuteron) targets

– Other reactions• γp → ρN, ωp, ππN • linearly polarized beams, polarized beam and

polarized targets



• R. Schumacher: polarization transfer in K+Λ photo and electro-production– Polarized beam, (recoil) polarization through its

weak decay asymmetry– New GRAAL results for recoil polarization P agree

with CLAS results– Large polarization transfer Cz along circularly

polarized photon beam direction– Find P2 + Cx

2 + Cz2 ' 1

• Models did not predict this• Bonn, Giessen, Gatchina (Sarantsev, Nikonov, Anisovich,

Klempt, Thoma ) fit with additional resonance P13(1860)• See talks by A. Sarantsev, V. Nikonov this meeting

– Beam asymmetry featureless (GRAAL, LEPS)




Expt. CLAS@Jefferson Lab


CLAS@Jefferson Lab

• V. Burkert, V. Mokeev– Q2 dependence of EM transition form

factors (0-6 GeV2) using CLAS@Jefferson Lab• Probes evolution of relevant degrees of freedom

in baryons • e-N ! ! N

– Dominant M1 contains non-resonant effects involving , at level of 30%

– Ratios of electric and scalar (quadrupole) multipoles to M1 measured to 0.5-2% over entire range of Q2

» Do not tend to pQCD limits

• e-N ! N½+(1440)! NN• Changes sign at Q2 ~ 0.5 GeV2 (seen in

relativistic models based on light-cone dynamics)– Consistent results using different analysis methods,

different final states

Expt.


Electron scattering labs…

• CLAS@Jefferson Lab pπ0nπ+

Nπ, pπ+π- nπ+

pπ0

DR UIM

Expt.


from analysis of CLAS 2data within the framework of JM06

from analysis of 1 CLAS data

combined analysis of 1 CLAS data

P11(1440) D13(1520)

Expt. Electron scattering labs…


• N3/2-(1520)D13

A1/2

A3/2

Q2, GeV2 Q2, GeV2

Previous pπ0

based data

preliminary

preliminary

PDG

pπ0nπ+

Nπ, pπ+π- nπ+

pπ0

Electron scattering labs…Expt.



• Cascade (0 ssu, - ssd) baryon program– Advantage that low-lying states are likely

narrow γp―>K+K+Ξ-* γp―>π-K+K+Ξ0*


BaBarExpt.

• Veronique Ziegler: e+e- annihilation at BaBar (results preliminary, under BaBar internal review)– Study 0(1530) in c

+ ! (-+) K+

• Indication is J=3/2 (confirms decuplet expectation)

– Study 0(1690) in c+ ! (K0) K+

• Preferred spin is J=1/2, some indication of negative parity

If negative parity, not Roper equivalent as some of us (!) thought

Much too light for quark model expectations of L=1 excited states N* + 2(ms-mu,d) !

Calculable on the lattice (D. Richards)


Crystal Barrel/TAPS@ELSAExpt.

• H. Schmieden: Physics at ELSA– Photoproduction of baryon resonances– ELSA

• photon beam energy (to 2.5 GeV)• Linear and circular polarization

– CB/TAPS • provides ~4 detection• Best for neutral final states

(missing mass for a charged particle) through their photon decays



• Goal: “complete” experiments on and photoproduction– Analysis simplified because only make N* (no

*)– Recent results:

• Unpolarized photoproduction of – Differential cross sections – From and 30! 6 decays of

• Linearly polarized photoproduction of (D. Elsner talk)



• D. Elsner: linearly polarized photoproduction of – Target

polarization – Consistent with

GRAAL results



• Photoproduction of off deuteron



• Data analysed to d/d

• Bonn-Gatchina PWA: see P11(1840)

• Polarization asymmetries R,



• Talk by E. Gutz: polarization asymmetry in

• Bonn-Gatchina PWA: (1940)D33



• Polarized photoproduction of

– Penner et al. and Shkylar (Giessen) analyses disagree


ANKE, TOF@COSYExpt.

• W. Schroeder– ANKE can see Y* states up to 1540 MeV, TOF

is best for threshold region• pp! pK+Y0*! pK+§ X¨

– Select events where X- = -, plot vs. MM(pK+):– Effect in X-+

at 1480 MeV,=60 MeV

– Also in X+-


ANKE, TOF@COSYExpt.

• ANKE: line shape of (1405)– Not Breit-Wigner, see talk by E. Oset this

meeting

L.S. Geng, E. Oset, arXiv: 0707.3343


ANKE, TOF@COSYExpt.

• TOF: – See no + pentaquark in pp! (pK0)+ or in

(pK0)+– Need polarized beam, target and detector

improvements to continue program of examining N*! YK in 1.6-1.9 GeV region

• New detector WASA ( and neutrals) will allow study of excited hyperonspp! pK+(1405)

! pK+00

! pK+()0


Crystal Ball/TAPS@MAMI

• M. Kotulla– Determination of magnetic moment of

(1232)• Use p! 0 0 p

Expt.


Crystal Ball/TAPS@MAMI

• Analysis effort underway– Pascalutsa and Vanderhaeghen, chiral

effective theory (good to E’ ~ 100 MeV)

– Sensitivity ~ 0.2 N

Expt.


BESII@IHEP

• W. Li: light hadron spectroscopy in J/ decays– New states:

, (masses and widths determined)• X(1835) in J/ ’

• X(1580) in J/ KK• Enhancement in J/ (1760) in J/

– N* observed in:• J/ pn ; J/ pp0 ; J/ nKS; Compared with (2S)

decay;– Some N*, e.g. N*(1535), N*(2065) better measured– Some branching fractions involving baryons are

measured

• Analysis of existing data ongoing• BEPCII/BESIII should collect data in 2008

Expt.


LNS@Sendai

• H. Shimizu: observation of N*(1670)– Have 300 MeV e- linac coupled to a 1

GeV synchroton– Use d ! X

• Also p ! X to subtract proton contribution

– Use -MAID analysis to understand p ! p• Interpret as new S11 at 1670 MeV, width

below 50 MeV, strong in n ! n• Not seen in proton channel

– Could this be an antidecuplet pentaquark?

Expt.


LEGS@BNL

• A. Sandorfi: Physics at LEGS– LEGS-Spin collaboration

• LEGS 2.8 GeV e- beam, backscattered laser beam, maximum photon energy ~430 MeV

• High circular polarization

– HD frozen spin• Hydrogen polarized or D polarized or both

– Mostly HD and a little H2 and D2 which feed HD polarized state (then decay away themselves, so HD spin frozen)

– Spin relaxation times ~ 1 year– Can transfer polarization from H to D

– Polarized photon + HD double-polarization physics• Measure various polarization asymmetries in inclusive

and exclusive HD ! X reactions on neutron– Use Lee Sato Matsuyama N! N amplitudes and fold into

D structure

Expt.


LEGS@BNL

• Analysis– Not a free neutron! Only half of the events

are quasi-free– Analysis of data on-going: separate § using

momentum analysis

• Targets and some of staff migrating from BNL to JLab– E06-101 (pol) + HD ! K0(pol), K0(pol), i.e.

n– Electron experiments on transversely

polarized target • GPDs, N* form factors, Collins/Sivers functions…

Expt.


MAMI@Mainz

• A. Thomas: Physics at MAMI– Virtual and real photons, linear and circular polarization– Three detectors Kaos,…,Crystal Ball/TAPS

• MAMI: – Harmonic double-sided microtron (electron accelerator)

• four bending magnets and two linacs– Energy 0.855-1.5 GeV

• Tagged photon and electron scattering experiments

• Experiments– Target asymmetry puzzle in and 0 production off proton

• Isobar models and Giessen models fail to describe– Electroproduction of at low Q2

• Cross section and recoil polarization– Single and double pion production – Helicity asymmetry in double-pion production

• Discrepancies with models

Expt.


MAMI@Mainz• Physics at MAMI:

– , 0 physics mass, rare decays (C,CP violation)Quark mass different mu-md in ! 30

0 ! 00 decays– GDH experiment @ MAMI-B with DAPHNE detector

(charged particle tracking)• Polarized butanol target with high deuteron polarization• MAMI/ELSA GDH sum rule 3/2-1/2

– Verified at 10% level• Also in exclusive reactions, important for PWAs

– Have for production– Photoproduction of p+-

• Helicity-dependent invariant mass distributions

• The future:– Frozen spin target for Crystal Ball—built this year– Recoil polarization of proton– Kaos—kaon electroproduction

Expt.


Theory developments

• Both lattice QCD and quark model calculations must face reality of light quark pairs– “Un-quenching” either is hard work– Requires calculation of couplings to

continuum states

• Coupled-channel analyses are becoming increasingly sophisticated– Need to preserve unitarity, gauge invariance,

and analytic structure, but remain manageable


Lattice QCD

• The nucleon and baryon resonances on the lattice: C. Gattringer (Graz-Regensburg), D. Richards (LHPC collaboration), A. Rusetsky– Recent important developments

• Basic quantities are Euclidean two and three-point functions

– Time dependence of two-point functions gives masses– Matrix elements in three-point functions give properties

• Extraction of excited state masses using carefully chosen basis of interpolators Oi

– Use these to construct a matrix of correlators– Solve eigenvalue problem to get accurate signal for mass

of excited states

Theory


Lattice QCD…

• Eigenvalues (t) vs. Euclidean time

Theory


Lattice QCD

– Recent important developments…• Hadron interpolators distributed over spatial

lattice points– LHPC collaboration, Graz-Regensburg

» classify into irreducible representations of lattice rotation group

» Allows nodes in radial wave function

• Can avoid chiral extrapolations by using chiral perturbation theory in a finite volume (small-scale expansion): See talk by A. Rusetsky, this meeting

– Luscher formalism developed for N scattering– Use statistical method to extract resonance mass

and width from lattice results– Demonstrated for (1232) mass and width

Theory


Lattice QCD…

• Spatially distributed interpolators– Much better overlap with excited states

Theory


Lattice QCD…

• Baryon spectrum, quenched calculations

Theory


Lattice QCD…Theory


Lattice QCD…

• Proton structure from three-point functions, chiral extrapolation to physical pion masses

• Different treatment of valence and sea quarks allows first look at chiral regime (un-quenched)– Isovector charge form factor (p-n)– Isovector charge radius

– Axial charge gA

– Moments of quark momentum fraction hxiu-d and helicity fraction hxiu -d

– Study of GPDs• Calculation of quark orbital angular momentum• Nucleon transverse size

Theory


Lattice QCD

• Lu and Ld substantial, total small

Theory


Lattice QCD

• Un-quenched calculations in development– Need clean separation of scattering states

once decays possible• Use different volume dependence of masses of

resonances and continuum states, large lattices

– Working on evaluating transition matrix elements (decay constants) for resonances

– Need contribution of disconnected diagrams (loops, gluons) to hadron structure

• Currently sensitive to statistical fluctuations

Theory


Models

• B. Borasoy: chiral corrections to the Roper resonance mass

• Lighter than its parity partner S11(1535)• 30-40% branch into N

– Parity order not settled in lattice QCD• Need reliable chiral extrapolation techniques• Use effective Lagrangian (N, Roper, ), calculate

mR(m2) to full 1-loop order (no explicit )

– Have R coupling = gA ' 1.26, RN coupling (0.3-0.4), 4 chiral parameters

– Infrared regularization scheme extended to one light scale (m) and two heavy (MN

2 << MR2)

– No strong m dependence near physical point

Theory


Models

• Constituent Quark Model: E. Santopinto, R. Bijker

• See also talk by Qiang Zhao, this meeting, on selection rules and quark correlations in the N* spectrum

• See also talk by A. Buchmann, this meeting, on calculation of higher (octupole) moments of baryons in pion-cloud quark model

– Tackle difficult problem of inclusion of next Fock space component in quark model

– Use large baryon-meson basis to expand qqq qq(bar)• Flux-tube breaking model gives overlap between qqq

and qqq qq(bar)• Checked that calculation returns usual CQM in closure

limit– Evaluate flavor asymmetry of nucleon sea

Theory


Models

• Results: significant difference from naïve nonrelativistic CQM results and relativistic CQM results– Closer to experiment and lattice QCD

Theory

u = 1.00 uexp= 0.82(5) uLQCD =0.79(11) uNRM = 4/3 uRQM = 1.01 d =-0.43 dexp= -0.44(5) dLQCD =-0.42(11) dNRM = -1/3 dRQM = -0.251 s =-0.06 sexp= -0.10(5) sLQCD =-0.12(11) sNRM =0 sRQM = 0


Models

• B. Metsch: Covariant constituent quark model– Based on instantaneous approximation to

Bether-Salpeter equation• Relativistic form of confining potential, chosen to

minimize spin-orbit effects• Instanton-based spin-spin interaction between

quarks

– Model parameters fit to spectrum• Calculate a host of other properties:

– Magnetic moments and charge radii» Including magnetic moments of excited states

– Resonance photocouplings and semi-leptonic decays– Strong two-body decay amplitudes

» Verifies pattern of decoupling of states not seen in analyses

Theory


Models

• B. Metsch: Covariant constituent quark model– Provides useful background against which to

search for unconventional states• Roper resonance EM couplings anomalous• Everything (mass, EM and strong couplings) about

the (1405) is anomalous• Hard to understand why the second band of

negative parity states [D35 and its partners] can be as low as ~1900 MeV

Theory


Models

• Chiral Unitary Approach: A. Ramos, E. Oset– KN I=0 JP=1/2- (S01) scattering state (1405) is

27 MeV below threshold• Looks like quasi-bound state

– Use chiral meson-baryon Lagrangian to generate an S-wave potential

– Need KN, , and K channels to fit decay branching ratios of this and nearby states

– Get two poles in T matrix approaching 1400 MeV when break SU(3)f gradually

• Explains why properties of (1405) depend on channel in which it is observed

Theory


Models

• (1405) in chiral unitary approach: pole positions move as break SU(3)f gradually

Theory


Models

– -p! K0N* mass ~1385 ~ 50 MeV– K-p! 000 mass ~1420 ~ 38 MeV

• Other baryons in the chiral unitary approach:– JP=1/2-: N*(1535), (1620), (1690)– JP=3/2-: (1700), (1520), (1670), (1820)

• From baryon decuplet interacting with meson 0- octet

– (1620); bump seen at Jefferson Lab in p! -K+K-()• Width is larger than width of invariant mass

distribution (near threshold) • [No claim for this state made in JLab experimental

paper;V. Burkert]

Theory


Models

• Chiral Unitary Approaches: A. Ramos– Heavy flavored baryons udc c(2593)

• DN s-wave molecule

• Predicts another c(2800), similar to experimental state

– Interaction of charmed mesons in hadronic medium D+D-

• Important for explaining J/ suppression in heavy-ion collisions

• Related to nucleon-antinucleon interactions

Theory


Models

• Chiral Unitary Approaches: E. Oset– (1405) is an interesting state

• See two poles in many models, one couples strongly to , the other to KN

– Experimental tests of (1405) structure • K-p ! (1405) • K-p ! 0(1405)• Radiative decay of two (1405) states

– Different shapes and rates for two states depending on reaction used

– K-p! 0, 00

• pp ! K+p(1405) measured by ANKE@COSY– Fit with kaon, pion and rho exchange diagrams

Theory


Models

• Excited baryons in 1/Nc expansion: C. Schat– How do we match quark models to 1/N_c?

• Useful perturbative expansion• Baryons fall into irreducible representations in large

N_c limit– N_c counting rules…– Quark operator expansion: Hmass= ciOi and fit

constants to baryon masses• Detailed calculations for L=1 baryons• To leading order: write down all operators with correct

properties– Have explicit flavor dependence (different from OGE)– Fit to 5 N=1 excited states; degenerate S11/D13 & D13/D15

pairs in large Nc limit– Orderings of singlet and two doublets not specified by 1/Nc

Theory


Models

• Excited baryons in 1/Nc expansion…– Extend using 1/Nc corrections and SU(3)f

– (1405) and (1520) split by spin-orbit operator

• What order is spin-orbit interaction?• Is core - exited quark separation

necessary?• How match to quark model?

– Consider:• One gluon exchange (general spatial dependence)• OPE (now explicit flavor dependence)

Theory


Models

• Shows using exchange symmetry that can calculate orbitally excited states using CCGL states– Expression for most general OGE and OPE mass operators

(different)– Constants written to leading order in overlap integrals

• Match forms to general form in 1/Nc

– OGE has c3=0 but fits in literature show not zero• Conclusion:

– SN analysis shows core and excited core basis necessary– Matching to quark models reproduces 1/Nc operator

expansion– Spin orbit is leading order, partial cancellation between LS

coming from OGE and OPE flavor dependent interactions– Matching method very general

Theory


SAID/MAID analyses

• B. Briscoe, George Washington University Data Analysis Center (SAID); L. Tiator, S. Kamalov Mainz (MAID)– Maintain important database for most reactions

including N*– On-line analysis tools important for single and coupled-

channel analysis of data– New analysis of N! N, photo and electro-production of

π0n, p by GWDAC: • 4-channel K-matrix N, N, , N up to 2.5 GeV• CLAS, CB-ELSA and GRAAL data• A1/2 from Nπ analysis for S11(1535) now agrees with Nη results

– Agrees with previous result from electro-production

• P13(1720) has large Ap1/2

– consistent with earlier analysis of pπ+π- in low Q2 electro-couplings

Expt.


Coupled-channel analysis

• A. Sibirtsev: Resonances in hadron-induced interactions

• See also talk by S. Krewald, this meeting, for a description of the Juelich coupled-channels approach to resonance analysis

– Need to match to Regge theory (pQCD) at very high energy

• Matches down to ~3 GeV, PWA stops at 2.4 GeV• Evidence of resonances in 2.4—3 GeV region?

– Through optical theorem find forward-pion charge-exchange indicates structures up to 3 or 4 GeV

• Also -p! 0n data show traces of high-mass baryons– Don’t neglect single-pion photoproduction for high

mass N*s (don’t stop calculating in models at 2 GeV)

Theory



• Giessen: V. Shklyar (G. Penner, U. Mosel, H. Lenske)– Data on

• Unitarity: optical theorem relates forward part of elastic scattering T matrix to inelastic c.s. to various channels (NEXT SLIDE)

» NOT UNRELATED!• Solve D-S eq’n in ladder approximation

– V has s, u and t-channel diagrams (matrix in channel space)

– Use effective Lagrangian approach (relativistic)– Solve Bethe-Salpeter equation by putting intermediate

particles on mass shell» Allows PW decomposition, equations become algebraic» Compare to SAID analysis PWs

• Works well for N but misses some PWs in N– Focus on p! p (and on neutron)

Theory


N, N total cross sections



p! p (and on neutron)– S11(1535) properties not well known,

complicates analysis in this region• Ratio of helicity amplitudes in N! N differs

from ! N• Fit GRAAL beam asymmetry data well, target

asymmetry not so well• Fit d/d for p ! p well, with S11(1650) giving

structure at 1670 MeV

– No need for new resonance in N– Destructive interference effect in -N! N

from S11(1650) and P11(1710) at higher mass explains “bump”

Theory



• Giessen: V. Shklyar– Narrow bump in differential c.s. n at 1670, is this a new

state?– GRAAL also see this bump (see talk by V. Kuznetzov)

• Non-strange partner of + ?• Exotic state?• Could S11(1650) and P11(1710) explain this effect at 1670 MeV?

– Look at all reactions simultaneously to make sure have treated these resonances properly

• Can fit with existing resonances, what price do you pay?– Need larger neutron photocoupling for S11

– S11(1650) properties agree with PDG P11(1710) is not as well known as *** implies!

• Change slightly size of 1650 An1/2, up comes bump in for n! n

SHOW GRAPH• Shape of differential c.s. not changed

– Cannot rule out narrow P11(1675), data not yet good enough• Be careful about Fermi motion in neutron state• Beam asymmetry may help

Theory



• MAID analysis: S. Kamalov (D. Drechsel, L. Tiator, S.N. Yang)– MAID 2007, recent results for pion photo and

electroproduction– Two-step process:

• Extract partial waves– Model dependence because of lack of data

• Extract resonance parameters from partial waves– Background and resonance T matrices

• Background: contains pion loop SHOW DIAGRAMS defined by K-matrix theory from background T-matrix

• Resonances dressed by pi N rescattering• Phase put into resonance piece to allow unitarity

(Watson’s theorem)

Theory



• MAID analysis: S. Kamalov– Pion/photoproduction data set now includes

GWU/SAID, Mainz, Bonn, GRAAL, LEGS– Results:

• S11(1535) photocouplings differ from SAID by a factor of 2, smaller than PDG

• P13(1720) shows up here, not in SAID

• See bump in P11 partial wave

– Fit an additional P11 at 1700 MeV, =30 MeV

– Electroproduction• Better data has improved situation

Theory



• MAID analysis: S. Kamalov– electroproduction

• A. Buchmann has parameterized E/M, S/M, and MAID fit to this form

• RSM(Q2) related to neutron EM form factors– Quite different S1+/M1+ than CLAS analysis

– Q2 dependence of A1/2 and A3/2 for first resonances in P11, S11, D13, and F15

• Helicity asymmetry changes sign in case of F15 also

Theory



• Bonn/Gatchina analysis: A. Sarantsev– Need polarization to sort out photoproduction– Technique:

• Relativistically invariant• Simultaneously analysis single and multiple-meson production• Specify energy dependence due to unitarity and analyticity

– Unitarize using K-matrix approach, has poles for resonances

• Doesn’t use real part of loops (real part smooth in physical region….)

• Use dispersion relations to put in below threshold (but not everywhere)

– Regge-ized t- and u-channel exchange amplitudes for background

– Use maximum likelihood method for three-particle final states N and N

• s-channel a product of two isobar terms

Theory



• Bonn/Gatchina analysis: results– Need -p! n00 at higher energy, fit well p! p00

• Find helicity 1/2 and 3/2 amplitudes• Help to establish properties of existing states• S11(1650) Ap

1/2 significantly larger than PDG• D13(1520) lower photocouplings than PDG and agree

with SAID 07• Roper has largest coupling to N• A1/2 has phase of residue of almost 90deg, sign different than PDG

– Eta photoproduction data from GRAAL stops at 1933 MEVclaim of new state N(2070)D15 requires double polarization data

– K CLAS/CB-ELSA (see Nikonov talk)• need P11(1860) and P13(1900)

– Fit to pi0 eta photoproduction total c.s. (Horn et al)• Need second D33(1940) at high energy• Need polarization data

Theory


Analysis

• Matt Bellis: CMU analysis technique– Event-based energy independent amplitude analysis

• Describe the events in a small energy bin with some set of processes

• Take out acceptance, get d\sigma/d\Omega• Get resonance terms, NR term, phase difference between

resonant terms• Use Rarita-Schwinger formalism (used by Bonn-Gatchina group)

– Don’t need energy dependence in s-channel propagator since bin in W

– Need to put in t and u-dependence into non-resonant terms• Find minimum set of diagrams which preserves gauge invariance

and describes data• See set of channels included (high statistics data sets) from CLAS

– Show K+, p results, unpolarized photon beam

Theory/Expt


Analysis

• Matt Bellis: CMU analysis technique– Close to finishing , K+ and /0

– Maintaining this as an active database– Requests from theorists to try out models

• Gauge invariance-have to put in complete set of diagrams

• Thresholds opening can change amplitudes within 10 MeV

Theory/Expt



• T.-S.H. Lee: Dynamical Coupled-channel Analysis by EBAC at Jefferson Lab– Structure of N* coupled to reaction channels

• Need to account for coupled-channel unitarity conditions

• Need reactions mechanism at short range

– Coupled-channel analysis based on effective Hamiltonian

• Re-examined N! N• Doing: N!N, N!N, N !N, electroproduction

Theory


NSTAR2007@Bonn 9/8/07-1 Simon Capstick, Florida State University.

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