S pin A symmetries of the N ucleon E xperiment

1. Measurement Of the Proton Form Factor Ratio at High Q2 by Using The Double Spin Asymmetries Spin Asymmetries of the Nucleon Experiment ( E07-003) Anusha Liyanage Hall C Users Meeting January 23, 2010

2. CONTENTS • Physics Motivation & HMS Kinematic • SANE Layout • Analysis Status • SIMC Simulation • Work Status

3. Physics Motivation & HMS Kinematic For Proton M. Jones et al., PRC74 (2006) 035201 RSS (Jlab) Q2 = 1.5 (GeV/c)2 Dramatic discrepancy ! between Rosenbluth and recoil polarization technique. GeP-III, Hall C

4. SANE Layout BETA (40°) HMS (14°- 48°) P e- BigCal Polarized Target Lucite Hodoscope ΘP Θe Gas Cherenkov Target Beam position monitor Forward Hodoscope Beam Line B at 80° OR 180°

5. From The Experiment The calculated asymmetry vsμGE/GM The raw asymmetry, The elastic asymmetry, The beam-target asymmetry, Here, N+= Helicity + Counts N- = Helicity - Counts At Q2=6.259 (GeV/C)2 PB,PT = Beam & Target Pol. f = Dilution Factor Nc = A Correction Term Am = AP = + Nc N+ - N- N+ + N- Am f PBPT PT+= ~71.0% , PT- = ~-65.0%,PB= ~73.0%, Ap = - br SinΘ*CosФ* - aCosΘ* r2 + c r = GE /GM Ap = - bSinΘ*CosФ* r - aCosΘ* c c a, b, c = kinematic factors Θ*,Ф* = pol. and azi. Angles between q and S Θ*≈ 102° and Ф* = 0 From the HMS kinematics, r2 << c

6. Error Propagation From The Experiment….. ∆Ap = bSinΘ*CosФ* ∆r c Using the experiment data at Q2=6.259 (GeV/C)2, ∆r = 0.118 μ ∆r = 2.79 x 0.118 μ ∆r = 0.3 Where ,μ – Magnetic Moment of the Proton The error on the μ ∆r from the experimental data with total ep events ~1000, μ ∆r = 0.3 Ap = - bSinΘ*CosФ* r - aCosΘ* c c

7. Analysis Status • HMS Detector Calibration is Completed. • Detector Efficiency. Modification of the DC tracking efficiency algorithm is done. (The tracking efficiency is increased by 15%-20%) • Extracted the elastic events. Correlation corrections are completed.

8. Tracking Efficiency Corrections Tracking Efficiency Vs Run Number • Used 4/6 DC hits instead of 5/6 DC hits. • Used the tracks which have stubs only on one of the DC’s as good tracks. Drift Chamber hits Vs x focal plane Ch1 Vs hsxfp Ch1 Vs hsxfp Ch2 Vs hsxfp Ch2 Vs hsxfp

9. Tracking Efficiency Correction Tracking Efficiency Vs x-focal plane Use the Tracking Efficiency as a function of hsxfp to correct data.

10. Extracted the elastic events Momentum Difference , dPel_hms Q2 = 4M2E2cos2Θ M2+2ME+E2sin2Θ ν = Q2 2M Pcal = Sqrt(ν2 + 2Mν) H M S C O IN Elliptic cut yi = variable ai = offset σi= cut HMS – abs(dPel_hms ) < 0.02 abs(hsdelta) < 8 hcer_npe < 0.2 hsshtrk/hse > 0.01 COIN - abs(EHMS-eclust+0.37) <1 abs(XHMS-xclust-0.15) < 5 abs(YHMS-yclust+0.41) < 10 dPel_hms = PHMS – Pcal Pcent

11. X/Y position difference X position Difference Y position Difference HMS cuts HMS cuts COIN cuts COIN cuts X_HMS - Xclust Y_HMS - Yclust X/Y_HMS – Predicted X/Y positions (Target Mag. Field Corrected)on the BigCal using the HMS kinematics X/Yclust - Measured X/Y positions on the BigCal Y_HMS - Yclust

12. Correlation Corrections for …. The dPel_hmsvssrast_y .... The Y position difference Vs srast _y …. dPel_hmsvssrast_y dPe_hmsvssrast_y Ydiff Vs srast_y Corrected dPel_hmsvssrast_y Corrected Ydiff Vs srast_y

13. SIMC Simulation HMS Single Arm Variables HMS Coincidence with BigCalVariables σ = 0.79 σ = 2.98 σ = 1.69 σ = 4.21 SIMC Simulation σ = 0.0041 Experimental Data σ = 0.0055 SIMC Counts = 1696 Data = 950 • Target Magnetic Field is corrected • Normalized to Charge, Tracking Efff. and Comp. L.T.

14. Work Status • HMS Calibration – completed • Preliminary elastic event selection – completed To Do ….. • Improve the SIMC simulation • Use the Data which are corrected with the new Tracking Efficiency correction function.(with hsxfp) • Include the new tracking algorithm to the simulation • Use the Efficiency Corrections • Extract the Asymmetry and the GE/GM Ratio