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Moscow, September 20-23, 2012 XIII International Seminar on Electromagnetic Interactions of Nuclei. Meson photoproduction and nucleon resonances. Eugene Pasyuk Jefferson Lab for the CLAS Collaboration. Outline. Introduction Experimental tools Single pion photporoduction

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meson photoproduction and nucleon resonances

Moscow, September 20-23, 2012

XIII International Seminar on

Electromagnetic Interactions of Nuclei

Meson photoproduction and nucleon resonances

Eugene Pasyuk

Jefferson Lab

for the CLAS Collaboration

outline
Outline

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

Introduction

Experimental tools

Single pionphotporoduction

K+Lphotoproduction

Summary

photonuclear cross sections
Photonuclear cross sections

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

baryon resonance spectrum
Baryon Resonance Spectrum

N*

Constituent quark model

Lattice QCD

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

Most models predict more resonance states than observed

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

polarization observables in pseudoscalar meson production
Polarization observables in pseudoscalar meson production

4Complex amplitudes: 16real polarization observables.

Complete measurement from 8carefully chosen observables.

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

πN

KY

recoil targγ

γ targrecoil

☻☻☻

☻☻☻

☻☻☻

☻☻☻

☻☻☻

☻☻☻

☻☻☻

☻☻☻

☻☻☻

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

Complete, and

over-determined

circ polarized photons

longitudinally polarized target

linearly polarized photons

transversely polarized target

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

from the experiment to theory
From the Experiment to Theory

Experiment

cross section,

spin observables

σ,dσ/dΩ,Σ,P,T

(beam-target) E,F,G,H,

(beam-recoil)Cx,Cz,Ox,Oz,

(target-recoil)Lx,Lz, Tx,Tz,

Amplitude analysis

→multipole amplitudes

→phase shifts

Reaction Theory

dynamical frameworks

Theory

LQCD,

quark models,

QCD sum rules,

Coupled channels:

resonance parameter

Extraction

This session

Hiroyuki Kamano

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

experimental tools
Experimental tools

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

cebaf
CEBAF

LINAC

LINAC

A

C

B

Injector

Experimental Halls

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

cebaf large acceptance spectrometer 1997 2012
CEBAF Large Acceptance Spectrometer1997-2012

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

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

polarized pohoton beam
Polarized pohoton beam

Circular polarization from 100% polarized electron beam

Circular polarization

Circularly polarized beam produced by longitudinally polarized electrons

Linearly polarized photons: coherent bremsstrahlung on oriented diamond crystal

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

frost
FROST

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

hdice polarized target
HDIce polarized target

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

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

what we measure with clas
What we measure with CLAS

γp→π0p, π+n

γp→ηp

γp→ηp

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, ηp, K+Λ provide isospin filter, directly coupled only to N*

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

single pion production
Single pionproduction

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

g p p n
gpp+n

•CLAS SP07 MAID07SP08SN08

M. 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

p p photon asymmetry s
pp Photon asymmetry S

DE=10 MeV

preliminary

Michael Dugger, ASU

Forum for MAX-IV Ring, Lund, Nov 2011

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

p p photon asymmetry s1
pp Photon asymmetry S

DE=10 MeV

preliminary

Michael Dugger, ASU

Forum for MAX-IV Ring, Lund, Nov 2011

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

g p p n photon asymmetry s
gpp+nPhoton asymmetry S

DE=10 MeV

preliminary

Michael Dugger, ASU

Forum for MAX-IV Ring, Lund, Nov 2011

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

g p p n helicity asymmetry e
gpp+nHelicityasymmetry E

preliminary

S. Strauch, USC

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

g p p n helicity asymmetry e1
gpp+nHelicity asymmetry E

preliminary

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.

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

g p p 0 p helicity asymmetry e
gpp0p Helicity asymmetry E

Michael Dugger, ASU

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

g p p n helicity asymmetry g
gpp+nHelicity asymmetry G

cos(qp)=-1 to -0.6

cos(qp)=-0.6 to -0.2

cos(qp)=-0.2 to 0.2

PRELIMINARY

PRELIMINARY

PRELIMINARY

cos(qp)=0.6 to 1.0

cos(qp)=0.2 to 0.6

PRELIMINARY

PRELIMINARY

Jo McAndrew

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

g p p n t arget asymmetry t
gpp+n Target asymmetry T

Michael Dugger, ASU

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

g p p n asymmetry f
gpp+n asymmetry F

F

F

F

F

F

F

F

F

F

F

F

F

Michael Dugger, ASU

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

k photoproduction
K+photoproduction

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

p k cross section
γpK+Λ Cross Section

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

p k cross section and p
γp→K+Λ: cross section and P

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

p k cx cz
γp→K+Λ: Cx/Cz

Nikonovet al’.’s refit of Bonn-Gachina multi-coupled-channel isobar model

mix 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

p k photon asymmetry s
γpK+ΛPhoton Asymmetry S

preliminary

C. Patterson

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

k l ox
K+L Ox

C. Patterson

preliminary

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

k l oz
K+L Oz

C. Patterson

preliminary

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

k l target asymmetry
K+L Target Asymmetry

C. Patterson

preliminary

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

k l helicity asymmetry e
K+L helicity asymmetry E

(PhD L. Casey, CUA)

preliminary

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

k l helicity asymmetry e1
K+L helicity asymmetry E

(PhD L. Casey, CUA)

preliminary

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

summary
Summary

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

status of meson photoproduction
Status of meson photoproduction

✔ -published✔- acquired

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

what was not shown
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

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

conclusion
Conclusion

“compete measurement” in pseudoscalar meson photoproductionis reality

Data collection with proton and deuteron targets is complete

Data are being analyzed

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

extras
Extras

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

h photoproduction
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

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

slide41
pp

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

SAID

MAID

NH (K. Nakayama and H. Haberzettl)

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

slide42
pp

M. Duggeret al. PRL 96, 062001 (2006)

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

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

variants of model
Variants of model

I

II

III

IV

V

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(1535)

S11(1650)

S11(2090)

P11(1710)

P11(2100)

P11(2400)

P13(1900)

D13(1700)

D13(2080)

gη´NN = 1.33

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(2090)

P11(1710)

P11(2100)

D13(1700)

D13(2080)

gη´NN= 0.002

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

slide44
pp

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

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

r values for the
R Values for the 

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

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

average r values
Average R values

Energy and angle averages are consistent with unity.

No model predicted this CLAS result.

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

polarization observables in pseudoscalar meson production1
Polarization observables in pseudoscalar meson production

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