Double and Single Target Asymmetries of Pion Electroproduction from JLab/CLAS EG4 Experiment Xiaochao Zheng University of Virginia April 22, 2009 The JLab/CLAS EG4 experiment overview EG4 exclusive channel analysis method Preliminary asymmetries from 3 GeV NH3 data Summary Acknowledgment: EG4 spokespeople: M. Battaglieri, R. De Vita, A. Deur, G. Dodge, M. Ripani, K. Slifer EG4 Ph.D. students (inclusive analysis): K. Adhikari, H. Kang, K. Kovacs Exclusive analysis CAA co spokespeople: A. Biselli, P.E. Bosted, G. Dodge Exclusive analysis CAA Review committee: D. Carman, P. Eugenio, C. Smith, M. Ungaro Other members from the EG1a and EG2000 collaborations X. Zheng, NSTAR 09, Beijing, China 1/32
Introduction The CLAS/EG4 experiment focused on measurement of the generalized GDH sums for p and n (D) at very low Q2 (0.01 0.5 GeV2): I GDH = M2 8 2 thr 1 / 2 3/ 2 d 1 2 2 I GDH Q =0 = 4 2 I GDH Q 0 = non perturbative perturbative 16 2 Q 2 x th 0 2 g1 x,q dx = 16 2 Q 2 1 Data at very low Q2 will test the chiral perturbation theory. (for an overview of the JLab spin physics/sum rules program, see A. Deur's talk this Monday afternoon.) Method: Extract helicity dependent inclusive cross sections, then extract g1; d d de ' d d de ' = 4 2 E '2 ME Q 2 2 2 [ E E ' cos g x, Q 2 M x g x, Q ] 1 2 X. Zheng, NSTAR 09, Beijing, China 2/32
The Accelerator (CEBAF) NORTH LINAC SOUTH LINAC INJECTOR RECIRCULATION ARCs (Magnets) A B C EXPERIMENTAL HALLS X. Zheng, NSTAR 09, Beijing, China 3/32
Experimental Hall B and the CEBAF Large Acceptance Spectrometer (CLAS) X. Zheng, NSTAR 09, Beijing, China 4/32
Experimental Hall B and the CEBAF Large Acceptance Spectrometer (CLAS) X. Zheng, NSTAR 09, Beijing, China 5/32
Short Carbon Long Carbon Short NH3 Long NH3 Empty X. Zheng, NSTAR 09, Beijing, China 6/32
EG4 Run Features Longitudinally polarized CLAS NH3 and ND3 targets at 1m w.r.t. CLAS center; New Cherenkov detector (INFN Genova) in sector 6 for detecting small angle scatterings down to 6o with uniform and high efficiencies; Low (1 3 GeV) beam energy, outbending torus field. X. Zheng, NSTAR 09, Beijing, China 7/32
EG4 Kinematic Coverage NH3 target (Ptarg= 80 90%) ND3 target (Ptarg= 30 45%) Extensive running at 1.3 GeV. X. Zheng, NSTAR 09, Beijing, China 8/32
EG1b Kinematic Coverage (for comparison) Lowest Eb: 1.6 GeV X. Zheng, NSTAR 09, Beijing, China 9/32
EG4 Run Overview Ran in Jan. April, 2006 New Cerenkov in Sector 6 built in the main trigger (~90% of events) # triggers normalized to PbPt=0.5 Eb (GeV) 1.1 1.3 1.5 2.0 2.2 3.0 1.3 2 # runs 161 175 25 65 66 115 117 172 # trigger events for (target, beam) (x108) (1,out) 30.6 25.0 5.7 4.1 4.2 9.4 4.8 5.0 (1,out) 21.3 20.8 0.0 8.7 4.6 10.1 3.7 4.9 ( 1,in) 8.4 9.9 0.0 0.0 2.6 4.2 0.0 0.0 ( 1,in) 15.6 9.8 0.0 0.0 3.0 3.1 0.0 0.0 Total trigger (x109) 7.4 6.4.57 1.9 1.4 2.7 0.85 0.96 Beam, target spin reversed nearly half way for most of energies. X. Zheng, NSTAR 09, Beijing, China 10/32
CC Performance New Cherenkov detector features nearly uniform efficiency within limited range (±10o) Fiducial cuts on sector 6 CC and in the projected PMT plane, study still underway (H. Kang) X. Zheng, NSTAR 09, Beijing, China 11/32
Electron Selection all e candidates pass calorimeter cuts pass Osipenko cuts <nphe> x10 <nphe> x10 inefficiencies using elastic electron events Use timing ( Osipenko ) cuts on CC w.r.t. other detectors; Efficiency study underway (H. Kang); intrinsic expected from Poisson Osipenko cuts <nphe> x10 <nphe> x10 X. Zheng, NSTAR 09, Beijing, China 12/32
Proton Elastic PbPt (H. Kang's work Seoul U.) E=3.0 GeV NH3 data, using elastic e p events to extract PbPt; Preliminary results agree with beam Moller (Pb=80%) and target NMR (Pt=75 76%). X. Zheng, NSTAR 09, Beijing, China 13/32
Expected Results from EG4 vs. EG1b Improvement (compared with EG1b) even better for ND3 X. Zheng, NSTAR 09, Beijing, China 14/32
Exclusive Channel Analysis Physics Motivation Nucleon resonances study; Mostly non perturbative, cannot use pqcd; Too light for lattice calculation; Must use effective theories or models: Constituent Quark Model: resonance amplitudes, helicity structure... (not on interference terms) Phenomenology models: MAID, SAID, DMT, JANR, Sato Lee ( )...... May compare to Chiral Perturbation Theory (very low Q2 only). Spin observables (asymmetries) provide constraints on: spin dependent amplitudes, interference terms... X. Zheng, NSTAR 09, Beijing, China 15/32
Observables in Pion Electroproduction e' Rea ctio n e * Cross section: d d. N ~ d unp d e d t d d d P e. Pt. P e P t. d et d.. * plan e * Sc att eri ng pla ne Three independent asymmetries: Single beam A e= Single target At = d e d unp d t d unp Double beam target A et = d et d unp = = = h e he h e he accessible from unpolarized target data h N h N h N h N only accessible from polarized target data h e, h N h e, h N he, h N h e, h N h e, h N h e, h N he, h N h e, h N X. Zheng, NSTAR 09, Beijing, China 16/32
EG4 Exclusive Channel Analysis Extract At and Aet from EG4 data for: NH3 target:. e p e ' n and e p e ' 0 p ND3 target: e n e '. p and e p e '. n Study dependence on Q2, W, * and cos * (binned in 4 simultaneously) Previous/other analyses: EG1a, EG1b; Our new results will help to constrain models and chiral perturbation theory at low Q2; Can compare to real photon experiment (FROST or HDice), study transition from virtual to real photons; Data on the neutron are rare. Ae sin d were extracted to check the beam /2 status for each run; X. Zheng, NSTAR 09, Beijing, China 17/32
Analysis Status and Very Preliminary Results for. e p e ' n using 3 GeV NH3 Data X. Zheng, NSTAR 09, Beijing, China 18/32
Pion Selection and Mx Cut Used TOF cut t t <1ns Missing mass cut: (0.85,1.05) GeV (e,e' +)n (e,e' +)n (one run) (one run) 4 2 0 2 4 ns 1 1.5 Mx (e' +) 2 GeV X. Zheng, NSTAR 09, Beijing, China 19/32
Charged Pion Exclusive Analysis Flow Charts (CLAS/EG4) 3 GeV NH3 Runs Experiment: E03 006 CLAS runs Feb May 2006 Legends: Not yet started In progress Completed Polarized N backgd e+ corrections PbPt Dilution factors Extracted Asymmetries Combining Runs Calibrations pion fiducial cuts Momentum corrections Raster corrections electron fiducial cuts Event selection, basic cuts Cooked Ntuples (pass 1) Run & file quality checks Radiative Corrections Acceptance Corrections Systematic Errors Models Results X. Zheng, NSTAR 09, Beijing, China 20/32
Dilutions Dilution factor measures fraction of events from polarized nucleons (p in NH3 and D in ND3) top: use low Mx region to line up carbon with NH3 0.5 0.6 0.7 0.8 0.9 GeV Mx bottom: use neutron peak to calculate dilution f f =0.207± 0.008 NH3 Carbon 0.8 0.9 1.0 1.1 1.2 GeV Mx In the following, will scale model by 0.2 to compare with data X. Zheng, NSTAR 09, Beijing, China 21/32
Aet vs. Q2 Data MAID2007 (x 0.20) r e V n i m i l re P y y r a (integrated over * and cos *) X. Zheng, NSTAR 09, Beijing, China 22/32
6 * bins At vs. W r e V 2 cos * ranges n i m i l re P y y r a Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 23/32
6 * bins Aet vs. W r e V 2 cos * ranges n i m i l re P y y r a Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 24/32
Q2 bins At vs. * r e V 2 cos * ranges n i m i l re P y y r a Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 25/32
Q2 bins At vs. * r e V 2 cos * ranges n i m i l re P y y r a Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 26/32
Q2 bins Aet vs. * r e V 2 cos * ranges n i m i l re P y y r a Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 27/32
Q2 bins Aet vs. * y r e V 2 cos * ranges y r a n i lim e r P Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 28/32
Overview of Data for all Beam Energies Eb Target # of runs with (beam,target) (GeV) ( 1, 1) ( 1,1) (1, 1) (1,1) 1.05 long NH3 19 69 32 34 1.34 long NH3 19 46 20 36 short NH3 0 26 0 28 2.00 long NH3 20 12 3 30 2.25 long NH3 10 8 8 16 short NH3 5 11 5 9 3.00 long NH3 21 33 16 31 1.34 long ND3 0 65 0 50 2.00 long ND3 0 118 0 122 # of (e,e' +)n evnts per run 5k 17k 14k 20k 20k 38k 22k DC sector status sec 1,4,5 off 3/4 runs had 1,4,5 off some had all sec on all sec on Will analyze At, Aet At, Aet 1/3 runs had 1,4,5 off, all At, Aet At, Aet had 5 off all had sec 5 off At, Aet all sec on Aet all sec on Aet Cannot study * dependence Rely on * integrations of Ae, At being zero. X. Zheng, NSTAR 09, Beijing, China 29/32
Aet vs. W, 3GeV NH3 Q2=(0.0919,0.156) Using all runs y r e V e r P y r a n i lim Using runs with target spin > 0 Using runs with target spin < 0 Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 30/32
Aet vs. W, 3GeV NH3 Q2=(0.156, 0.266) Using all runs r e V P y i l re n i m y r a Using runs with target spin > 0 Using runs with target spin < 0 Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) X. Zheng, NSTAR 09, Beijing, China 31/32
Summary Using EG4 data can Extract pion electroproduction asymmetries At and Aet at very low Q2; Provide inputs to MAID, SAID, DMT; Hoping to compare to Chiral Perturbation Theory calculations. Analysis well underway and preliminary exclusive channel asymmetry results from the 3GeV NH3 data are very promising; Stay tuned for our new results! X. Zheng, NSTAR 09, Beijing, China 32/32
CLAS/EG4 vs. Hall A/SAGDH Kinematic Coverage Hall B(CLAS) EG4 NH3 (proton) Hall A E97 110 Polarized 3He (neutron) (talk by V. Sulkosky yesterday) X. Zheng, NSTAR 09, Beijing, China 33/32
CLAS/EG4 vs. Hall A/SAGDH Expected Inclusive Channel Results Can combine 1p and 1n to form the Bjorken sum (see next talk). X. Zheng, NSTAR 09, Beijing, China 34/32
Back up Slides X. Zheng, NSTAR 09, Beijing, China 35/32
run 50801 (sec 5 off) 0 60 120 run 50765 (all sec on) 0 60 120 180 *, (e,e' +)n240 180 240 300 300 electron in sec 6, pion in: sector 1 sector 2 sector 3 sector 4 sector 5 sector 6 360 *, (e,e' +)n sum of all sectors + 360 *, (e,e' )n X. Zheng, NSTAR 09, Beijing, China 36/32
Physics Motivation (cont.) Example: Roper P11(1440) Least understood and most controversial Sensitivity of Aet (n +) to P11(1440): Eb=1.34 Q2=0.1 cos *=0.4 *=20o (MAID2000) (JANR) PRC67, 015209 (2003) Figure credit: C. Smith X. Zheng, NSTAR 09, Beijing, China 37/32
Physics Motivation (cont.) Sensitivity of At (n +) to P11(1440): Eb=1.34 Q2=0.1 cos *=0.4 *=60o (MAID2000) (JANR) PRC67, 015209 (2003) Figure credit: C. Smith X. Zheng, NSTAR 09, Beijing, China 38/32
Physics Motivation (cont.) Sensitivity of At (p 0) to P11(1440): Spin observables may help to remove some model dependence in extraction of amplitudes -> better determination of the nature of P11(1440). (MAID2000) Eb=1.34 Q2=0.1 cos *= 0.8 *=50o (JANR) PRC67, 015209 (2003) Figure credit: C. Smith X. Zheng, NSTAR 09, Beijing, China 39/32
Radiation Length Study (by P. Konczykowski) E = 1.34 GeV X. Zheng, NSTAR 09, Beijing, China 40/32
Simulations (V. Drozdov and M. Ripani) E = 1.339 GeV, NH3 data (using 0.6 packing factor) 2 Q =0.03 0.04 GeV 2 2 Q =0.06 0.07GeV 2 2 Q =0.12 0.13GeV 2 reconstructed data simulation X. Zheng, NSTAR 09, Beijing, China 41/32