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yawei@jlab

Measurements of Target Single-Spin Asymmetries in QE 3 He ↑ (e, e’). Update of QE A y (E05-015) experiment. Yawei Zhang. Rutgers University. yawei@jlab.org. Slide 0. Hall A Collaboration Meeting. Outline. Physics motivation. Existing world data.

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yawei@jlab

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  1. Measurements of Target Single-Spin Asymmetries in QE 3He↑(e, e’) Update of QE Ay (E05-015) experiment Yawei Zhang Rutgers University yawei@jlab.org Slide 0 Hall A Collaboration Meeting

  2. Outline • Physics motivation. • Existing world data. • Experiment setup and kinematics. • Target performance during experiment. • Preliminary results. • Summary and future plan. yawei@jlab.org Slide 1 Hall A Collaboration Meeting

  3. Physics Motivation e-N scattering: 2 … Leading contributor Higher order terms 2g physics: Study the contribution of higher order terms yawei@jlab.org Slide 2 Hall A Collaboration Meeting

  4. Physics Motivation How do we know that an asymmetry is due to 2g physics? 2 X = + Born Term X + X + Interference Term Higher order transition amplitude: A. DeRujula et al., Nuc. Phys. B35 (1971) 365 Born Approximation: Include 2g exchange: Real has an imaginary part N. Christ and T.D. Lee, Phys. Rev. 143, 1310 (1966) yawei@jlab.org Slide 3 Hall A Collaboration Meeting

  5. Existing World Data • A high-enough precision measurement does not exist! • Make a precise non-zero measurement of Ay. • Provide quantitative information about the imaginary part of the two-photon exchange process. • 2-photon-exchange process provides a new way to study nucleon structure, in this case, an integral of GPDs. Proton Data yawei@jlab.org Slide 4 Hall A Collaboration Meeting

  6. Theoretical Prediction Expected result -1.35 yawei@jlab.org Slide 5 Hall A Collaboration Meeting

  7. Experiment Setup & Kinematics QE Ay experiment (E05-015) was run from April 26th to May 12th in 2009 at Jefferson Lab Hall A yawei@jlab.org Slide 6 Hall A Collaboration Meeting

  8. Polarized 3He Target 86% 1.5% 12% F. R. P. Bissey, A. W. Thomas, and I. R. Afnan, Phys. Rev. C64, 024004 (2001) Why 3He? No free neutrons – they decay in less than 15 minutes! 3He and Deuteron are two good candidates for a neutron target. In 3He the protons are nearly unpolarized, but in the Deuteron the proton and neutron are equally polarized. yawei@jlab.org Slide 7 Hall A Collaboration Meeting

  9. Polarized 3He Target Laser Beam Pumping Chamber (Polarization happens here) Transfer Tube Electron Beam Target Chamber (Nuclear physics happens here) yawei@jlab.org Slide 8 Hall A Collaboration Meeting

  10. Hall A Polarized 3He Target • Newlasers Narrow line lasers make more efficient optical pumping. • 3D Holding Field Control New vertical coil together with existing horizontal coils create holding field in any direction. • New Oven and Optics Better insulation, lighter weight and all three pumping directions. • A Smart Target Automatic spin flip every 20 minutes using Adiabatic Fast Passage (AFP). Log and alarm. yawei@jlab.org Slide 9 Hall A Collaboration Meeting

  11. Wow, 3D! Magnetic Field yawei@jlab.org Slide 10 Hall A Collaboration Meeting

  12. Target Performance During Ay <P>=51.4%+/-0.8%(Rel. stat.) +/- 5.4% (Rel. sys.) yawei@jlab.org Slide 11 Hall A Collaboration Meeting

  13. Detector Package 1). A pair of Vertical Drift Chambers (VDCs) determine the trajectory of particles; 2). Two scintillator planes (S1 and S2) generate the trigger and the time-of-flight information; 3). A Gas Cerenkov detector separates e-/π-; 4). A preshower and a shower counter give additional e-/π- separation. yawei@jlab.org Slide 12 Hall A Collaboration Meeting

  14. Events Selection yawei@jlab.org Slide 13 Hall A Collaboration Meeting

  15. Preliminary Results at Q2=0.98 GeV2 Preliminary yawei@jlab.org Slide 14 Hall A Collaboration Meeting

  16. Preliminary Results • The asymmetry is clearly non-zero. • Precision is anorder of magnitude improved over. yawei@jlab.org Slide 15 Hall A Collaboration Meeting

  17. Summary • Electron Ay results from QE region: • It is the first time to measure Ay with high-precision (~10-4 level) on a neutron target. • For Q2=0.98 GeV2 data, original analysis was done by B. Zhao, two independent cross checks have been done by Ellie and Yawei. • Q2=0.46 GeV2 results is available. • Ay is clearly non-zero and consistent between L-arm and R-arm data. • Future Plan: • Finish the Q2=0.13 GeV2data analysis. • Radiativecorrections. • Proton dilution. • Finalize systematic uncertainties. yawei@jlab.org Slide 16 Hall A Collaboration Meeting

  18. Acknowledgement • Thanks to the Hall A Quasi-Elastic Family of Experiments. • Thanks to the spokespeople: T. Averett (E05-015, E08-05), J. P. Chen (E05-015), S. Gilad(E05-102), D. Higinbotham(E05-102, E08-005), X. Jiang(E05-015), W. Korsch(E05-102), B. E. Norum(E05-102), S. Sirca(E05-102), V. Sulkosky (E08-005). • Graduate students: G. Jin, E. Long, M. Mihovilovič, Y. Zhang • Hall A collaborations. yawei@jlab.org Slide 17 Hall A Collaboration Meeting

  19. Backup 1 In terms of GPD moments Y.C. Chen etc., PRL 93, 122301 (2004) A measurement of Ay has sensitivity to GPD model input yawei@jlab.org Hall A Collaboration Meeting Backup Slide 1

  20. Backup 2 • What has been done: • Detector calibrations has been done for both HRS. (2009-2010) • Target density and wall thickness measurement has been done. (2009-2010) • Target internal temperature tests has been done. (2009-2010) • Target data quality check has been done. (2009-2010) • Detectors stability check has been done. (2010-2011) • Data quality check has been done. (2010-2011) • Target polarization at pumping chamber has been calculated. (2011-2012) • Use of different cuts to select the good electrons has been studied. (2011-2012) • Raw target single spin asymmetries have been extracted. (2011-2012) Different technical notes are available for different analysis parts. yawei@jlab.org Hall A Collaboration Meeting Backup Slide 2

  21. Backup 3 yawei@jlab.org Backup Slide 3 Hall A Collaboration Meeting

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