Eugene Pasyuk Jefferson Lab for the CLAS Collaboration Moscow, September 20-23, 2012 XIII International Seminar on Electromagnetic Interactions of Nuclei.

Meson photoproduction and nucleon resonancesEugene Pasyuk

Jefferson Labfor the CLAS Collaboration

Moscow, September 20-23, 2012XIII International Seminar onElectromagnetic Interactions of Nuclei

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2E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

*Outline

*Introduction

*Experimental tools

*Single pion photporoduction

*K+L photoproduction

*Summary

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*Photonuclear cross sections

E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

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*Baryon Resonance Spectrum

*Masses, widths, and coupling constants not well known for many resonances

*Most models predict more resonance states than observed

N*

Constituent quark model

Lattice QCD


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* Polarization observables in pseudoscalar meson production

4 Complex amplitudes: 16 real polarization observables.

Complete measurement from 8 carefully chosen observables.

πN has large cross section but in KY recoil is self-analysing

I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).

πN KY

recoil targ γ

γ targ recoil

☻☻☻

☻

linearly polarized photons

☻☻☻☻☻☻

longitudinally polarized target

☻☻☻☻☻☻

circ polarized photons

☻☻☻☻☻☻

☻☻☻☻☻☻

transversely polarized target

Complete, andover-determined


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*From the Experiment to Theory

Experimentcross section,

spin observables

TheoryLQCD,

quark models,QCD sum rules,

…

Reaction Theorydynamical frameworks

Amplitude analysis→multipole amplitudes

→phase shifts

σ,dσ/dΩ,Σ,P,T

(beam-target) E,F,G,H,(beam-recoil) Cx,Cz,Ox,Oz,(target-recoil) Lx,Lz, Tx,Tz,

Coupled channels: resonance parameter

ExtractionThis session

Hiroyuki Kamano


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*Experimental tools


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A B CInjector

LIN

AC L

INA

CExperimental Halls

*CEBAF

* E: 0.75 –6 GeV

* Imax: 200μA

* Duty Cycle: 100%

* δE/E: 2.5x10-5

* Polarization: ≥85%

* Simultaneous distribution to 3 experimental Halls


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*CEBAF Large Acceptance Spectrometer1997-2012

Torus magnet6 superconducting coils

Gas Cherenkov counterse/ separation, 256 PMTs

Time-of-flight countersplastic scintillators, 684 photomultipliers

Drift chambers35,000 cells

target + start counter

Electromagnetic calorimetersLead/scintillator, 1296 photomultipliers


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*Polarized pohoton beamC

ircu

lar

pola

riza

tion

Circular polarization from 100% polarized electron beam

Linearly polarized photons: coherent bremsstrahlung on oriented diamond crystal

Circularly polarized beam produced by longitudinally polarized electrons


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*FROST


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HDIce Solid Deuterium-Hydride (HD) – a new class of polarized target

*HDIce polarized target

* Polarized at very high magnetic field and very low temperature

* Transferred to in-beam cryostat

* Spin can be moved between H and D with RF transitions

* All material can be polarized with almost no background


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*What we measure with CLAS

* γp→π0p, π+n* γp→ηp* γp→ηp* γp→KY (K+Λ, K+Σ0, K0Σ+)* γp→π+π-p, ωp, ρp, ϕp

* γn→π-p* γn→π+π-n* γn→Σ-K+ , ΛK0 …..

Reactions γp→ηp, ηp, K+Λ provide isospin filter, directly coupled only to N*


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*Single pion production

E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 14

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*gpp+n

•CLAS SP07 MAID07 SP08 SN08M. Dugger et al. PRC 79, 065206 (2009)

Constrained SAID fit at higher energies. Does not need any new resonances


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16Forum for MAX-IV Ring, Lund, Nov 2011

DE=10 MeV

*pp Photon asymmetry S

preliminary

Michael Dugger, ASUE. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

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DE=10 MeV

*pp Photon asymmetry S

Michael Dugger, ASU

preliminary


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DE=10 MeV

*gpp+n Photon asymmetry S

Michael Dugger, ASU

preliminary


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*gpp+n Helicity asymmetry E

preliminary

S. Strauch, USCE. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

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*gpp+n Helicity asymmetry E

For W< 1.75 GeV all of the models represent the data fairly well.For W> 1.75 GeV none of the models represents the data well.

preliminary


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*gpp0p Helicity asymmetry E


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PRELIMINARY

PRELIMINARY

PRELIMINARY

PRELIMINARY

PRELIMINARY

cos(qp)=-1 to -0.6 cos(qp)=-0.6 to -0.2 cos(qp)=-0.2 to 0.2

cos(qp)=0.2 to 0.6 cos(qp)=0.6 to 1.0

*gpp+n Helicity asymmetry G

Jo McAndrew )2sin()2cos(10

GPPPd

d

d

dzTT


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*gpp+n Target asymmetry T


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F F F

F F F

F

F

FF

F F

*gpp+n asymmetry F


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*K+ photoproduction

E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 25

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*γpK+Λ Cross Section


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recoil polarization P

excitation function

g11: W=1.7 – 2.8 GeV(unpolarized beam & target)

M.E. McCracken et al., PRC 81, 025201 (2010)

*γp→K+Λ: cross section and P


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*γp→K+Λ: Cx/Cz

Nikonov et al’.’s refit of Bonn-Gachina multi-coupled-channel isobar modelmix includes: S11 wave, P13(1720), P13(1900), P11(1840)

Bradford et al. PRC 75, 035205 (2007),


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*γpK+Λ Photon Asymmetry S

preliminary

C. Patterson


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*K+L OxC. Patterson

preliminary


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*K+L OzC. Patterson

preliminary


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*K+ L Target AsymmetryC. Patterson

preliminary


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(PhD L. Casey, CUA)

*K+ L helicity asymmetry E

preliminary


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(PhD L. Casey, CUA)

*K+ L helicity asymmetry E

preliminary


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*Summary


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*Status of meson photoproduction

σ Σ T P E F G H Tx Tz Lx Lz Ox Oz Cx Cz

Proton target

pπ0 ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓

nπ+ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓

pη ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓

pη’ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓

pω ✔ ✓ ✓ ✓ ✓ ✓ ✓

K+Λ ✔ ✓ ✓ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔

K+Σ0 ✔ ✓ ✓ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔

K0*Σ+

✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓

“Neutron” target

pπ- ✔ ✓ ✓ ✓ ✓ ✓ ✓

pρ- ✓ ✓ ✓ ✓ ✓ ✓ ✓

K+Σ- ✓ ✓ ✓ ✓ ✓ ✓ ✓

K0Λ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

K0Σ0 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

K0*Σ0

✓ ✓

✔ - published ✔ - acquired


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*What was not shown* γp→ηp* γp→η’p* γp→π+π-p ωp, ρp, ϕp

* γn→π-p* γn→π+π-n* γn→Σ-K+ , ΛK0 …..

We have measured cross sections an polarization observables


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*Conclusion

*“compete measurement” in pseudoscalar meson photoproduction is reality

*Data collection with proton and deuteron targets is complete

*Data are being analyzed


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*Extras


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*h’ photoproduction

* 1968: 11 events from the ABBHHM bubble chamber experiment

* 1976: 7 events from the AHHM streamer chamber experiment

* 1998: 250 events from the SAPHIR collaboration (first differential cross sections)

* 2006: over 2×105 events from the CLAS collaboration

*2009: another few orders of magnitude from CLAS g11 data set


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*pp

* SAID

* MAID

* NH (K. Nakayama and H. Haberzettl)

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M. Dagger et al. PRL 96, 062001 (2006)


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*pp

K. Nakayama and H. Haberzettl, Phys. Rev. C 73, 045211 (2006).

Different versions of the model yield similar results for cross section, but quite different predictions for beam asymmetry

Predictions for beam asymmetry are quite different

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M. Dugger et al. PRL 96, 062001 (2006)


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*Variants of model

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S11(1535)S11(1650)S11(2090)

P11(1710)P11(2100)

P13(1720)P13(1900)

D13(1520)D13(1700)D13(2080)

gηŃN = 1.91

S11(2090)

P11(2100)

P13(1900)

D13(1700)

gηŃN = 0.43

S11(2090)

P11(2100)

P13(1900)

D13(1700)D13(2080)

gηŃN = 0.25

S11(1535)S11(1650)S11(2090)

P11(1710)P11(2100)P11(2400)

P13(1900)

D13(1700)D13(2080)

gηŃN = 1.33

S11(1535)

S11(2090)

P11(1710)P11(2100)

D13(1700)D13(2080)

gηŃN = 0.002

I II III IV V


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*pp

M. Williams et al. PRC 80, 045213 (2009)

44E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

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*R Values for the

The appears 100% polarized when created with a fully polarized beam.

2 2 2x zR P C C


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*Average R values

*Energy and angle averages are consistent with unity.

*No model predicted this CLAS result.

1 .01 0 .01R ±


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*Polarization observables in pseudoscalar meson production


Eugene Pasyuk Jefferson Lab for the CLAS Collaboration Moscow, September 20-23, 2012 XIII International Seminar on Electromagnetic Interactions of Nuclei.

Documents

p p

reactions p p

n n

summary slide

polarized beam

clas collaboration moscow

qcd sum rules qcd sum

beamrecoil c x