X. Zheng, NSTAR 09, Beijing, China 1 /32 Double and Single-Target Asymmetries of Pion Electroproduction from JLab/CLAS EG4 Experiment The JLab/CLAS EG4 experiment — overview EG4 exclusive channel analysis method Preliminary asymmetries from 3 GeV NH3 data Summary Xiaochao Zheng University of Virginia April 22, 2009 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 2 /32 Introduction Method: Extract helicity-dependent inclusive cross sections, then extract g 1 ; The CLAS/EG4 experiment focused on measurement of the generalized GDH sums for p and n (D) at very low Q 2 ( GeV 2 ): Data at very low Q 2 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.) non- perturbative perturbative

X. Zheng, NSTAR 09, Beijing, China 3 /32 EXPERIMENTA L HALLS INJECTO R RECIRCULATIO N ARCs (Magnets) NORTH LINAC SOUTH LINAC C B A The Accelerator (CEBAF)

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 Experimental Hall B and the CEBAF Large Acceptance Spectrometer (CLAS)

X. Zheng, NSTAR 09, Beijing, China 6 /32 Short NH 3 Empty Long NH 3 Short Carbon Long Carbon

X. Zheng, NSTAR 09, Beijing, China 7 /32 EG4 Run Features Longitudinally polarized CLAS NH 3 and ND 3 targets at -1m w.r.t. CLAS center; New Cherenkov detector (INFN-Genova) in sector 6 for detecting small angle scatterings down to 6 o with uniform and high efficiencies; Low (1-3 GeV) beam energy, outbending torus field.

X. Zheng, NSTAR 09, Beijing, China 8 /32 EG4 Kinematic Coverage NH 3 target (P targ = 80-90%) ND 3 target (P targ = 30-45%) Extensive running at 1.3 GeV.

X. Zheng, NSTAR 09, Beijing, China 9 /32 EG1b Kinematic Coverage (for comparison) Lowest Eb: 1.6 GeV

X. Zheng, NSTAR 09, Beijing, China 10 /32 EG4 Run Overview Ran in Jan.-April, 2006 New Cerenkov in Sector 6 built in the main trigger (~90% of events) Beam, target spin reversed nearly half-way for most of energies. # triggers normalized to PbPt=0.5

X. Zheng, NSTAR 09, Beijing, China 11 /32 CC Performance New Cherenkov detector features nearly-uniform efficiency within limited f range (±10 o ) Fiducial cuts on sector 6 CC q and f in the projected PMT plane, study still underway (H. Kang)

X. Zheng, NSTAR 09, Beijing, China 12 /32 Use timing (“Osipenko”) cuts on CC w.r.t. other detectors; Efficiency study underway (H. Kang); Electron Selection “intrinsic ” “Osipenko cuts” expected from Poisson inefficiencies using elastic electron events all e- candidates pass calorimeter cuts pass Osipenko cuts x10

X. Zheng, NSTAR 09, Beijing, China 13 /32 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%). Proton Elastic PbPt (H. Kang's work – Seoul U.)

X. Zheng, NSTAR 09, Beijing, China 14 /32 Expected Results from EG4 vs. EG1b Improvement (compared with EG1b) even better for ND3

X. Zheng, NSTAR 09, Beijing, China 15 /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 (D) May compare to Chiral Perturbation Theory (very low Q 2 only). Spin observables (asymmetries) provide constraints on: spin-dependent amplitudes, interference terms...

X. Zheng, NSTAR 09, Beijing, China 16 /32 f*f* q*q* g*g* p Observables in Pion Electroproduction e e' Cross section: Three independent asymmetries: Single-beam Single-target Double beam-target accessible from unpolarized target data only accessible from polarized target data Scattering plane Reaction plane N

X. Zheng, NSTAR 09, Beijing, China 17 /32 EG4 Exclusive Channel Analysis Extract A t and A et from EG4 data for: NH3 target: and ND3 target: and Study dependence on Q 2, W, f* and cosq*— (binned in 4 simultaneously) Previous/other analyses: EG1a, EG1b; Our new results will help to constrain models and chiral perturbation theory at low Q 2 ; Can compare to real photon experiment (FROST or HDice), study transition from virtual to real photons; Data on the neutron are rare. were extracted to check the beam l/2 status for each run;

X. Zheng, NSTAR 09, Beijing, China 18 /32 Analysis Status and Very Preliminary Results for using 3 GeV NH3 Data

X. Zheng, NSTAR 09, Beijing, China 19 /32 Pion Selection and Mx Cut Used TOF cut |t-tp|<1ns Missing mass cut: (0.85,1.05) GeV ns GeV Mx (e'p + ) (e,e'p + )n (one run)

X. Zheng, NSTAR 09, Beijing, China 20 /32 Extracted Asymmetries Polarized N backgd e + corrections Dilution factors PbPt Calibrations Cooked Ntuples (pass 1) Cooked Ntuples (pass 1) Run & file quality checks Run & file quality checks Event selection, basic cuts Combining Runs Raster correction s Raster correction s Momentum corrections Momentum corrections electron fiducial cuts electron fiducial cuts pion fiducial cuts Acceptanc e Correction s Radiativ e Correcti ons Experiment: E CLAS runs Feb-May 2006 Experiment: E CLAS runs Feb-May 2006 Systemati c Errors Results Models Charged Pion Exclusive Analysis Flow Charts (CLAS/EG4) 3 GeV NH3 Runs Complete d In progress Not yet started Legends:

X. Zheng, NSTAR 09, Beijing, China 21 /32 Dilutions Dilution factor measures fraction of events from polarized nucleons (p in NH3 and D in ND3) In the following, will scale model by 0.2 to compare with data NH3 Carbon GeV Mx GeV Mx top: use low Mx region to line up carbon with NH3 bottom: use neutron peak to calculate dilution f

X. Zheng, NSTAR 09, Beijing, China 22 /32 Aet vs. Q 2 ➢ (integrated over f* and cosq*) Very Preliminary MAID2007 (x-0.20) Data

X. Zheng, NSTAR 09, Beijing, China 23 /32 Very Preliminary 6 f* bins At vs. W Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) 2 cosq* ranges

X. Zheng, NSTAR 09, Beijing, China 24 /32 Very Preliminary 6 f* bins 2 cosq* ranges Aet vs. W Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 25 /32 Very Preliminary Q2 bins 2 cosq* ranges At vs. f* Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 26 /32 Very Preliminary Q 2 bins 2 cosq* ranges At vs. f* Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 27 /32 Very Preliminary Q 2 bins 2 cosq* ranges Aet vs. f* Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 28 /32 Very Preliminary Q 2 bins 2 cosq* ranges Aet vs. f* Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 29 /32 Overview of Data for all Beam Energies Cannot study f*-dependence Rely on f* integrations of Ae, At being zero.

X. Zheng, NSTAR 09, Beijing, China 30 /32 Aet vs. W, 3GeV NH3 Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off) Very Preliminary Using all runs Using runs with target spin > 0 Using runs with target spin < 0 Q2=(0.0919,0.156)

X. Zheng, NSTAR 09, Beijing, China 31 /32 Very Preliminary Using all runs Using runs with target spin > 0 Using runs with target spin < 0 Q2=(0.156, 0.266) Aet vs. W, 3GeV NH3 Data; MAID2007; DMT; MAID2007(P11off); MAID2007(S11off); MAID2007(D13off)

X. Zheng, NSTAR 09, Beijing, China 32 /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 33 /32 CLAS/EG4 vs. Hall A/SAGDH Kinematic Coverage Hall B(CLAS) EG4 NH 3 (proton) Hall A E Polarized 3 He (neutron) (talk by V. Sulkosky yesterday)

X. Zheng, NSTAR 09, Beijing, China 34 /32 CLAS/EG4 vs. Hall A/SAGDH Expected Inclusive Channel Results Can combine G 1 p and G 1 n to form the Bjorken sum (see next talk).

X. Zheng, NSTAR 09, Beijing, China 35 /32 Back-up Slides

X. Zheng, NSTAR 09, Beijing, China 36 /32 f*, (e,e'p + )n run (sec 5 off) run (all sec on) f*, (e,e'p + )n electron in sec 6, pion in: sector 1 sector 2 sector 3 sector 4 sector 5 sector 6 sum of all sectors

X. Zheng, NSTAR 09, Beijing, China 37 /32 Physics Motivation (cont.) Example: Roper P 11 (1440) -- Least understood and most controversial Sensitivity of Aet (np + ) to P 11 (1440): (MAID2000) Eb=1.34 Q2=0.1 cosq*=0.4 f*=20 o Figure credit: C. Smith (JANR) PRC67, (2003)

X. Zheng, NSTAR 09, Beijing, China 38 /32 Physics Motivation (cont.) Sensitivity of At (np + ) to P 11 (1440): Figure credit: C. Smith Eb=1.34 Q2=0.1 cosq*=0.4 f*=60 o (MAID2000) (JANR) PRC67, (2003)

X. Zheng, NSTAR 09, Beijing, China 39 /32 Physics Motivation (cont.) Sensitivity of At (pp 0 ) to P 11 (1440): Figure credit: C. Smith Eb=1.34 Q2=0.1 cosq*= f*=50 o Spin observables may help to remove some model dependence in extraction of amplitudes -> better determination of the nature of P 11 (1440). (MAID2000) (JANR) PRC67, (2003)

X. Zheng, NSTAR 09, Beijing, China 40 /32 E = 1.34 GeV Radiation Length Study (by P. Konczykowski)

X. Zheng, NSTAR 09, Beijing, China 41 /32 E = GeV, NH 3 data (using 0.6 packing factor) Simulations (V. Drozdov and M. Ripani) reconstructed data simulation