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![Page 1: Eugene Pasyuk Jefferson Lab for the CLAS Collaboration Moscow, September 20-23, 2012 XIII International Seminar on Electromagnetic Interactions of Nuclei.](https://reader031.fdocuments.net/reader031/viewer/2022012922/56649e3f5503460f94b2f91e/html5/thumbnails/1.jpg)
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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*Experimental tools
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*FROST
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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*
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*Single pion production
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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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17Forum for MAX-IV Ring, Lund, Nov 2011
DE=10 MeV
*pp Photon asymmetry S
Michael Dugger, ASU
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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18Forum for MAX-IV Ring, Lund, Nov 2011
DE=10 MeV
*gpp+n Photon asymmetry S
Michael Dugger, ASU
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*gpp0p Helicity asymmetry E
Michael Dugger, ASUE. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*gpp+n Target asymmetry T
Michael Dugger, ASUE. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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F F F
F F F
F
F
FF
F F
*gpp+n asymmetry F
Michael Dugger, ASUE. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*K+ photoproduction
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*γpK+Λ Cross Section
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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),
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*γpK+Λ Photon Asymmetry S
preliminary
C. Patterson
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*K+L OxC. Patterson
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*K+L OzC. Patterson
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*K+ L Target AsymmetryC. Patterson
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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(PhD L. Casey, CUA)
*K+ L helicity asymmetry E
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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(PhD L. Casey, CUA)
*K+ L helicity asymmetry E
preliminary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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*Summary
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012
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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)
41
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
42
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)
gη´NN = 1.91
S11(2090)
P11(2100)
P13(1900)
D13(1700)
gη´NN = 0.43
S11(2090)
P11(2100)
P13(1900)
D13(1700)D13(2080)
gη´NN = 0.25
S11(1535)S11(1650)S11(2090)
P11(1710)P11(2100)P11(2400)
P13(1900)
D13(1700)D13(2080)
gη´NN = 1.33
S11(1535)
S11(2090)
P11(1710)P11(2100)
D13(1700)D13(2080)
gη´NN = 0.002
I II III IV V
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*pp
M. Williams et al. PRC 80, 045213 (2009)
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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
E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012