Hyperon production and polarization with CLAS at JLab
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Transcript of Hyperon production and polarization with CLAS at JLab
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Sergio Anefalos Pereira
Laboratori Nazionali di Frascati(for the CLAS Collaboration)
Hyperon production and polarization with Hyperon production and polarization with CLAS at JLabCLAS at JLab
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IntroductionIntroduction A major goal of hadron physics is to probe the structure of the nucleon and
its excited states.◦ The N* spectrum is a direct reflection of the underlying degrees of freedom of the
nucleon.
Symmetric ConstituentQuark Models predict ahigher number of excitedstates
Quark and flux-TubeModels predict increased number of states
Quark-Diquark modelspredict fewer states
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Löhring, Metsch, Petry, EPJ A10, 395(2001)
1. Quark models predict many more baryons that have been observed, “missing” resonances;
2. Many baryon resonances are predicted studying the channels with π, but very few were established;
Missing ResonancesMissing Resonances
The CLAS program is designed to obtain accurate electromagnetic production cross section and spin observables over a broad kinematic range. Strangeness production is an important part of this program.
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Why studying KY ?Why studying KY ?
Self-analyzing weak decay of hyperons allows recoil polarization measurements with high statistics:• polarization observables are crucial to extract elementary amplitudeshigh discriminating power against various models• one can have access to all observables (not possible with channels)
To resolve the question of “missing” resonances• have information about the structure of the nucleon• Couplings of nucleon resonances to KY final states will differ
from the πN, ηN and ππN final states.
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CLAS
• Continuous Electron Beam• Energy 0.8-5.7 GeV• 200A, polarization 85%• Simultaneous delivery to 3Halls
JLab Accelerator CEBAF
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Hall B: Cebaf Large Acceptance Spectrometer
Torus magnet6 superconducting coils
Electromagnetic calorimetersLead/scintillator, 1296 photomultipliers
beam
Drift chambersargon/CO2 gas, 35,000 cells
Time-of-flight countersplastic scintillators, 684 photomultipliers
Gas Cherenkov counterse/ separation, 216 PMTs
Liquid D2 (H2)target + start counter; e minitorus • Broad angular coverage (8° 140° in LAB frame)
• Charged particle momentum resolution ~0.5% forward dir
CLAS is designedto measure exclusive reactions with multi-particle final states
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2coscoscos
cos2sincos
cos2sincos
2cos1
''
''''
''''0
TPP
CPOP
CPOP
P
dd
yy
zzzz
xxxx
Define the Spin ObservablesDefine the Spin Observables (unpolarized target)(unpolarized target)
proton
zyx
z
y
x
zyx
p
. .c mK
proton
K+P
P
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2coscoscos
cos2sincos
cos2sincos
2cos1
''
''''
''''0
TPP
CPOP
CPOP
P
dd
yy
zzzz
xxxx
proton
zyx
z
y
x
zyx
p
. .c mK
proton
K+P
P
Define the Spin ObservablesDefine the Spin Observables (unpolarized target)(unpolarized target)
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2coscoscos
cos2sincos
cos2sincos
2cos1
''
''''
''''0
TPP
CPOP
CPOP
P
dd
yy
zzzz
xxxx
proton
zyx
z
y
x
zyx
p
. .c mK
proton
K+P
P
Define the Spin ObservablesDefine the Spin Observables (unpolarized target)(unpolarized target)
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Polarization observables in pseudoscalar meson productionPolarization observables in pseudoscalar meson production
4 Complex amplitudes: 16 real polarization observables.
Complete measurement from 8 carefully chosen observables.
Only hyperon can provide recoil polarization
I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).
BTR
Nrecoil targ γ
KYγ targ recoil
linearly polarized photonscirc polarized photons
longitudinally polarized targettransversely polarized target
complete andover-determined
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11
16 Pseudoscalar Meson 16 Pseudoscalar Meson Photoproduction ObservablesPhotoproduction Observables
Single PolarizationSingle Polarization
Beam & TargetBeam & Target
Beam & RecoilBeam & Recoil
Target & RecoilTarget & Recoil
{{{{{{{{
For + p K+ :
C. Paterson et al. (Glasgow), to be published
C. Paterson et al. (Glasgow), to be published
R. Bradford et al. Phys. Rev. C 73 035202 (2006), M.E.McCracken et.al., PRC 81, 025201 (2010)
J. McNabb et al. Phys Rev C 69 042201 (2004)
R. Bradford et al. Phys. Rev. C 75 035205 (2007), M.E.McCracken et.al., PRC 81, 025201 (2010)
FROST (g9a) under analysis
FROST (g9a) under analysis
FROST (g9b) under analysis
FROST (g9b) under analysis
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neutron channels are almost unexplored add constraints in the resonance extractions.
study Final State Interaction: Compare bound proton and free proton results Study YN interactions
Photoproduction on neutronsPhotoproduction on neutrons(deuteron target)(deuteron target)
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Neutron experiments @ CLASNeutron experiments @ CLAS
Polarized (g13) data process ongoing Target: 40cm liquid deuterium Data taking: October 2006 – June 2007 Circular polarized beam
E = 0.4 – 2.5 GeV Linear polarized beam
E = 1.1 - 2.3 GeV Integrated luminosity: ~ 90 pb−1
Unpolarized (g10) Final data set with several published papers Target: 24cm liquid deuterium Data taking: March 13 - May 16, 2004 E(): 0.75-3.58 GeV Integrated luminosity: ~ 50 pb−1 γn (p) → K+ Σ – (p)
neutron cross sections
n (p)K0 (p)n (p)K0 (p) neutron cross sections and spin observables
n (p) K+ (p)n (p) K+* (p)n (p) K+* (p)
neutron cross sections and beam asymmetry
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γγ n(p) n(p) →→ K K++ ΣΣ (p) cross sections(p) cross sections CLAS 2010 LEPS 2006 Regge-3 model
• first “complete” look at hyperon production off neutron
• deuteron target (spectator proton) FSI ~ 10%
• Ghent model with K+ and K*(892) with no resonances
S. Anefalos Pereira et. al., Phys.Lett.B 688 (2010)
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• first “complete” look at hyperon production off neutron
• deuteron target (spectator proton) FSI ~ 10%
• Ghent model with K+ and K*(892) with no resonances
γγ n(p) n(p) →→ K K++ ΣΣ (p) cross sections(p) cross sections
• Hint of u- channel contribution for higher energies (back angle rise)
S. Anefalos Pereira et. al., Phys.Lett.B 688 (2010)
CLAS 2010 LEPS 2006 Regge-3 model
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PREL
IMIN
A
RY
G13G13 preliminary beam asymmetry results preliminary beam asymmetry results n n KK00 (Neil Hassal, Glasgow)
1.3 GeV 1.5 GeV 1.7 GeV
1.9 GeV 2.1 GeV 2.3 GeV
KK corrected
MAID - P11, P13, S11, D13MAID - no D13
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PREL
IMIN
A
RY
G13G13 preliminary beam asymmetry results preliminary beam asymmetry results n n KK00 (Neil Hassal, Glasgow)
KMAID – P11, P13, S11, S31
MAID - P11, P13, P31, S11, S31MAID – S11, P11, P13 MAID - P11, P13, P31, S11
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Measurements on n (Deuterium) target Measurements on n (Deuterium) target
• Circularly and linearly polarized photons on n (g13, Deuterium target)• γ n → K+ Σ- analysis for polarization observables underway. Edwin Munevar, GWU
Edwin Munevar, GWU
PRELIMIN
ARY
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Rescattering study with G13Rescattering study with G13
Free and quasi-free protonQuasi free neutron good approx. to free
p (n)nRussell Johnstone, Glasgow
(comparing H2 (g8) and D2 (g13) data)
phot
on a
sym
met
ry r
atio
(fre
e / q
uasi-
free
p)
Coscm (-1.0 to +1.0)
PREL
IMIN
ARY1.1 – 1.3 GeV1.3 – 1.5 GeV 1.5 – 1.7 GeV
1.7 – 1.9 GeV 1.9 – 2.1 GeV
Indicates that quasi-free neutron is a good approximation to a free neutron
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SummarySummary
• KY photoproduction offer kinematic and analysis advantages in N* physics;
• CLAS detector provides very precise measurements in a broad kinematic range;
• Published CLAS KY results on proton (, P, Cx, Cz) and more observables to be published soon (Ox, Oz,G, E, Lx, Lz);
• Neutron channels are almost unexplored;• Deuteron target can be used to study FSI, comparing bound and free
proton, as well as YN interactions;• Cross sections results on the neutron in a wide photon energy and angular
range has been obtained with CLAS with g10 experiment. Analysis with g13 data are ongoing and more will come with HD-Ice.
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Backup slides
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FROSTFRozen Spin Target (C4H9OH – polarized butanol) with longitudinal and transverse polarization
Entire repolarization procedure takes under 6 hoursTake data for 5-6 days
Excellent reliability! Excellent reliability!
Result Design
Polarization +82% (80%) -85%
1/e relaxation time 2800h (+) (500h) 1600h (-)
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New polarized target (H D )
HD-IceHD-Ice target for polarised neutrons
Designed to run with both photon and electron beams
Under construction! 04/20 to 05/05/2011 production running 05/05 to 05/12/2011 electron beam test run
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Photoproduction on protonsPhotoproduction on protons• Unpolarized cross sections
• Single beam polarization
• Recoil polarization
• Double polarization (Beam and Recoil) – Circular polarized beam– Linear polarized beam
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ppKK++ Total Cross Sections Total Cross Sections
• Two bump structure seen
• CLAS/SAPHIR disagreement
R. Bradford et al. Phys. Rev. C73 035202 (2006)
Missing resonance?
CLAS 06 SAPHIR 04 SAPHIR 98 ABBHM
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Differential cross section of Differential cross section of ppKK++
full line: full model with additional S11, P13 and D13 resonancesdotted line: no S11 resonancedot-dashed line: no P13 resonancedashed line: no D13 resonance
Alternative approaches propose other contributions for the resonance-like structure at 1.9 GeV:
• D13 (Bennhold & Mart)• P13 (Nikanov et al.)• P11 (Ghent model)• KKN bound state (Martinez Torres et al.)
Coupled-channel approach by Julia-Diaz et al. (PRC73,055204)
new predicted bound state with a mix of a0(980)N and f0(980)N
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broader energy range, better statistics, good agreement between CLAS 2006 (Bradford et al.) and new CLAS 2010 data set.
Different data set, different trigger, different analysis chain
1.6 1.8 2.0 2.2 2.4 2.6 2.8 S (GeV)
d/d
cos
c.m
. (
b)K
CLAS McCracken 2010 CLAS Bradford 2006 SAPHIR 2004
M.E.McCracken et.al., PRC 81, 025201 (2010)
Differential cross section of Differential cross section of ppKK++
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1.62 GeV
2.84 GeV
Differential cross section of Differential cross section of ppKK++
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• Single-bump: resonance-like structure near 1.9 GeV– N* & D resonances
• Better agreement with SAPHIR than
R. Bradford et al. Phys. Rev. C73 035202 (2006)
CLAS 06 SAPHIR 04 SAPHIR 98 ABBHM
Total cross section of Total cross section of ppKK++ 00
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broader energy range, better statistics, good agreement between CLAS 2006 (Bradford et al.) and new CLAS 2010 data set.
Different data set, different trigger, different analysis chain
B. Dey et.al. arXiv:1006.0374v2 [nucl-ex]submitted to Phys. Rev. C
CLAS 10 CLAS 06 SAPHIR 04
Differential cross section of Differential cross section of ppKK++ 00
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Photoproduction on protonsPhotoproduction on protons• Unpolarized cross sections
• Single beam polarization
• Recoil polarization
• Double polarization (Beam and Recoil) – Circular polarized beam– Linear polarized beam
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CLAS g8b improved results - CLAS g8b improved results - KK++linearly polarized photon asymmetry
• Wider range• Improved precision• Good agreement among CLAS, GRAAL and LEPS• Results for pK+coming as well
PREL
IMIN
AR
Y
Increase the angular coverage to backward angles
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• Wider range• Improved precision• Good agreement among CLAS, GRAAL and LEPS• Results for pK+coming as well
PRELIMINARY
CLAS g8b improved results - CLAS g8b improved results - KK++linearly polarized photon asymmetry
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• Wider range• Improved precision• Good agreement among CLAS, GRAAL and LEPS• Results for pK+coming as well
PREL
IMIN
AR
Y
Increase the angular coverage to backward angles
CLAS g8b improved results - CLAS g8b improved results - KK++linearly polarized photon asymmetry
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• Wider range• Improved precision• Good agreement among CLAS, GRAAL and LEPS• Results for pK+coming as well
PRELIMINARY
Increase the angular coverage to backwardangles
CLAS g8b improved results - CLAS g8b improved results - KK++linearly polarized photon asymmetry
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• Wider range• Improved precision• Good agreement among CLAS, GRAAL and LEPS• Results for pK+coming as well
PRELIMINARY
Increase the angular coverage to backwardangles
CLAS g8b improved results - CLAS g8b improved results - KK++linearly polarized photon asymmetry
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Photoproduction on protonsPhotoproduction on protons• Unpolarized cross sections
• Single beam polarization
• Recoil polarization
• Double polarization (Beam and Recoil)– Circular polarized beam– Linear polarized beam
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ppKK++ Hyperon Recoil Polarization Hyperon Recoil Polarization
Kaon-MAIDGENT Regge model GLV
R. Bradford et al., Phys. Rev. C 75, 035205 (2007).S. Anefalos Pereira 38April 13 - DIS2011
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ppKK++ Hyperon Recoil Polarization Hyperon Recoil Polarization CLAS McCracken 2010 CLAS McNabb 2004 SAPHIR 2004 GRAAL 2007
Wider range Improved
precision More detailed
structure now visible!
CLAS PWA in progress
Good agreement among CLAS, SAPHIR and GRAAL
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ppKK++ Hyperon Recoil Polarization Hyperon Recoil Polarization CLAS McCracken 2010 CLAS McNabb 2004 SAPHIR 2004 GRAAL 2007
Wider range Improved
precision More detailed
structure now visible!
CLAS PWA in progress
Good agreement among CLAS, SAPHIR and GRAAL
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ppKK++00 Hyperon Recoil Polarization Hyperon Recoil Polarization
Wider range Improved
precision More detailed
structure now visible!
CLAS PWA in progress
Good agreement among CLAS, SAPHIR and GRAAL
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ppKK++00 Hyperon Recoil Polarization Hyperon Recoil Polarization
Wider range Improved precision More detailed structure now visible! CLAS PWA in progress in three angular bins (0.3,
0.5 and 0.7) there are few isolated discrepancies between CLAS data that is not clear yet. Studies underway.
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Photoproduction on protonsPhotoproduction on protons• Unpolarized cross sections
• Single beam polarization
• Recoil polarization
• Double polarization (Beam and Recoil)– Circular polarized beam– Linear polarized beam
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Results: CResults: Czz for K for K++
Guidal, Laget, VanderhaeghenShklyar, Lenske, and MoselKaon-MAID
Julia-Diaz, Lee, Saghai,Tabakin Corthals, Ryckebusch, and Van
CauterenSarantsev and Nikonov
Janssen, Ryckebusch
R. Bradford et al., Phys. Rev. C 75, 035205 (2007).
Very large transfer along Very large transfer along zz
Poor performance by pre-2007 modelsPoor performance by pre-2007 models
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Results: CResults: Cxx for K for K++R. Bradford et al., Phys. Rev. C 75, 035205 (2007).
Poor performance by pre-2007 modelsPoor performance by pre-2007 models
Guidal, Laget, VanderhaeghenShklyar, Lenske, and MoselKaon-MAID
Julia-Diaz, Lee, Saghai,Tabakin Corthals, Ryckebusch, and Van
CauterenSarantsev and Nikonov
Janssen, Ryckebusch
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Effect of including CLAS data in modelsEffect of including CLAS data in models
Kaon-MAID
multipole model
V. A. Nikanov et al., Phys Lett. B 662, 246 (2008).see also: A.V. Anisovich et al., Eur. Phys J. A 25 427 (2005).
• Nikanov et al’.’s refit of Bonn-Gachina multi- coupled- channel isobar model
• mix includes: S11-wave, P13(1720), P13(1900), P11(1840)
• P13(1900) is not found in quark-diquark models.
CxCz without N*(1900)P13 CxCz with N*(1900)P13
pK+ pK+czcx
the CLAS data is very important to constraint theoretic models
E. Santopinto Phys Rev. C 72, 022201(R), (2005)S. Anefalos Pereira 46April 13 - DIS2011
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Total polarization for the Total polarization for the
- No model predicted this CLAS result.
1.01 0.01R
2 2 2x zR P C C
“Fully Polarized ”
RΣ0 = 0.82 0.03
–- For 0 channel no full polarization has been observed
Confirmed by GRAAL: A. Lleres et al. Eur. Phys. J. A 39, 149 (2009)
S. Anefalos Pereira 47April 13 - DIS2011
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Photoproduction on protonsPhotoproduction on protons• Unpolarized cross sections
• Single beam polarization
• Recoil polarization
• Double polarization (Beam and Recoil)– Circular polarized beam– Linear polarized beam
S. Anefalos Pereira 48April 13 - DIS2011
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ppKK++(g8b)(g8b)Beam-Recoil OBeam-Recoil Oxx and O and Ozz
KaonMAID; RPR2-Regge only; RPR2-core; RPR2-w/D13
Strong differences to the model predictions. These data will improve model capability.
1
0
-1
S. Anefalos Pereira 49April 13 - DIS2011
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ppKK++(g8b)(g8b)Beam-Recoil OBeam-Recoil Oxx and O and Ozz
KaonMAID; RPR2-Regge only; RPR2-core; RPR2-w/D13
Strong differences to the model predictions. These data will improve model capability.
1
0
-1
S. Anefalos Pereira 50April 13 - DIS2011
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ppKK++(g8b)(g8b)Beam-Recoil OBeam-Recoil Oxx and O and Ozz
KaonMAID; RPR2-Regge only; RPR2-core; RPR2-w/D13
Strong differences to the model predictions. These data will improve model capability.
1
0
-1
S. Anefalos Pereira 51April 13 - DIS2011