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

Eugene Pasyuk

Jefferson Lab

for the CLAS Collaboration

* * Introduction * Experimental tools * Single pion photporoduction * K + L photoproduction * Summary `

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* `

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Constituent quark model ` * Masses, widths, and coupling constants not well known for many resonances * Most models predict more resonance states than observed

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Lattice QCD

* 4 Complex amplitudes:

real polarization observables.

Complete measurement from

carefully chosen observables. πN has large cross section but in KY recoil is self-analysing ☻

πN

recoil targ γ γ

targ recoil ☻☻☻ ` ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻

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

circ polarized photons linearly polarized photons longitudinally polarized target transversely polarized target

E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 Complete, and over-determined 5

* Experiment cross section, spin observables σ,dσ/dΩ,Σ,P,T (beam-target) E,F,G,H, (beam-recoil) (target-recoil) C x ,C z ,O x ,O z , L x ,L z , T x ,T z , Amplitude analysis → multipole amplitudes → phase shifts Reaction Theory dynamical frameworks ` Theory LQCD, quark models, QCD sum rules , …

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Coupled channels: resonance parameter Extraction This session Hiroyuki Kamano

* `

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Injector

A B C Experimental Halls E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012

* * * * * * E: 0.75 –6 GeV I max : 200μA Duty Cycle: 100% δE/E: 2.5x10

-5 Polarization: ≥85% Simultaneous distribution to 3 experimental Halls

CEBAF Large Acceptance Spectrometer 1997-2012

Torus magnet

6 superconducting coils

Electromagnetic calorimeters

Lead/scintillator, 1296 photomultipliers

target + start counter Drift chambers

35,000 cells `

Time-of-flight counters

plastic scintillators, 684 photomultipliers

Gas Cherenkov counters

e/  separation, 256 PMTs

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* Circular polarization from 100% polarized electron beam ` Circularly polarized beam produced by longitudinally polarized electrons Linearly polarized photons: coherent bremsstrahlung on oriented diamond crystal

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* `

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* HDIce Solid Deuterium-Hydride (HD) – a new class of 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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* * * * * * γp → π 0 p, π + n γp → ηp γp → η  p γp → KY (K + Λ, K + Σ 0 , K 0 Σ + ) γp → π + π p, ωp, ρp, ϕ p * * * γn → π p γn → π + π n γn → Σ K + , ΛK 0 …..

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

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* `

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* ` •CLAS SP07 MAID07 SP08 SN08 M. Dugger et al. PRC 79, 065206 (2009) Constrained SAID fit at higher energies.

Does not need any new resonances

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* D

E=10 MeV

W = æ

d d

s W æ 0 ( 1 -

lin

S cos2 f )

Forum for MAX-IV Ring, Lund, Nov 2011 E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 Michael Dugger, ASU 16

* D

E=10 MeV

Forum for MAX-IV Ring, Lund, Nov 2011 E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 Michael Dugger, ASU 17

* D

E=10 MeV

Forum for MAX-IV Ring, Lund, Nov 2011 E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 Michael Dugger, ASU 18

* `

W =

s 0

W ( 1 -

circ P z E

) S. Strauch, USC

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* `

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.

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* `

E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 Michael Dugger, ASU 21

cos(

q 

)=-1 to -0.6

PRELIMINARY cos(

q 

)=-0.6 to -0.2

cos(

q 

)=-0.2 to 0.2

PRELIMINARY cos(

q 

)=0.2 to 0.6

PRELIMINARY PRELIMINARY cos(

q 

)=0.6 to 1.0

PRELIMINARY



 



 0  1 

P T

 cos( 2  ) 

P T P z G

sin( 2  ) 

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

Jo McAndrew

* `

W =

s 0

W ( 1 +

P y T

)

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* F F F F F F F F F F F `

W =

s 0

W ( 1 +

P x P

circ F

P y T

) F

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* `

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* `

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

excitation function M.E. McCracken et al., PRC 81, 025201 (2010) E. Pasyuk, EMIN-2012, Moscow, September 20-23 2012 27

* Nikonov S11 wave, P11(1840) et al’ of Bonn-Gachina multi-coupled channel isobar model mix includes: P13(1720), P13(1900), .’s refit ` Bradford et al . PRC 75, 035205 (2007),

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* `

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C. Patterson

* C. Patterson `

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* C. Patterson `

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* C. Patterson `

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(PhD L. Casey, CUA)

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(PhD L. Casey, CUA)

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` *

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σ Σ T pπ 0 nπ + pη pη’ pω K + Λ K + Σ 0 K 0* Σ +

✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

pπ pρ K + Σ K 0 Λ K 0 Σ 0 K 0* Σ 0

✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

P E

✓ ✓ ✓ ✓ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

G H T x

Proton target ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ` ✓ ✓ ✓ ✓ ✓ ✓ ✓

T z L x L z O x O z C x C z

✓ ✓ ✓ ✓ ✔ - published ✔ - acquired

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

✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

* * * * γp → ηp γp → η’p γp → π + π p ωp, ρp, ϕ p * * * γn → π p γn → π + π n γn → Σ K + , ΛK 0 …..

We have measured cross sections an polarization observables `

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Conclusion

* “compete measurement” in pseudoscalar meson photoproduction i s reality * Data collection with proton and deuteron targets is complete * Data are being analyzed `

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` *

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* * 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 2×10 5 events from the CLAS collaboration * 2009: another few orders of magnitude from CLAS g11 data set

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* ` * * SAID MAID * NH (K. Nakayama and H. Haberzettl) M. Dagger et al. PRL 96, 062001 (2006)

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* ` 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 M. Dugger et al. PRL 96, 062001 (2006) Predictions for beam asymmetry are quite different

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S 11 (2090) P 11 (2100)

III

S 11 (1535) S 11 (1650) S 11 (2090) P 11 (1710) P 11 (2100) P 11 (2400)

S 11 (1535) S 11 (2090) P 11 (1710) P 11 (2100) S 11 (1535) S 11 (1650) S 11 (2090) P 11 (1710) P 11 (2100)

P 13 (1900) P 13 (1900) P 13 (1900) ` D 13 (1700) D 13 (1700) D 13 (2080) D 13 (1700) D 13 (2080) D 13 (1700) D 13 (2080) g

η ´

NN = 0.43

η ´

NN = 0.25

η ´

NN = 1.33

η ´

NN = 0.002

P 13 (1720) P 13 (1900) D 13 (1520) D 13 (1700) D 13 (2080) g

η ´

NN = 1.91

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

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

2 

C x

2 

C z

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

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= * Energy and angle averages are consistent with unity.

* No model predicted this CLAS result.

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* `

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