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Extraction of G E n at Q 2 =1 (GeV/c) 2 by Measurements of

May 1, 2011 Ge Jin University of Virginia. Extraction of G E n at Q 2 =1 (GeV/c) 2 by Measurements of. Abstract. G E n was extracted for the first time by inclusive polarized measurements of

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Extraction of G E n at Q 2 =1 (GeV/c) 2 by Measurements of

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  1. May 1, 2011 Ge Jin University of Virginia Extraction of GEn at Q2=1 (GeV/c)2 by Measurements of

  2. Abstract • GEn was extracted for the first time by inclusive polarized measurements of • Getting the ratio of asymmetries in longitudinal and transverse target polarization; separating the electric and magnetic form factor contributions • Proton and neutron contributions calculated in PWIA • New technique, confirms previous measurements; uncertainty: ~18%, largely statistical

  3. Previous measurements and extraction of GEn • Rosenbluth separation • Polarization transfer d(e,e’n)p • Polarized scattering, neutron tagging • Polarized inclusive quasi-elastic scattering

  4. Previous extractions of GEby • Uncertainties comparable to measured quantity

  5. Detectors and kinematics of this measurement • Detectors: • HRS-R: detect electrons, placed at 170 • Kinematics: • Beam energy: 3.6 GeV • Q2: 1 (GeV/c)2

  6. Polarized 3He target • Room-temperature gaseous (10 atm) target • Rb-K hybrid optical pumping and spin exchange • Average polarization ~55%

  7. Analysis in asymmetries • Beam polarization: by Hall A Möller measurements • Target polarization: by run-by-run NMR calibration • Dilution factor: by N2 pressure curve • Radiative correction: by formalism of Mo and Tsai, peaking approximation of Steil, et al. Code used in JLab E94010 for inelastic 3He scattering

  8. Transverse-longitudinal asymmetry ATL’(target polarization perpendicular to q) • Near quasi-elastic peak 0.9<xBj<1.1, ATL’=(-0.55±0.09 (stat)±0.04 (syst))%

  9. Transverse asymmetry AT’(target polarization parallel to q) • Near quasi-elastic peak 0.9<xBj<1.1, AT’ =(3.12±0.10 (stat)±0.21 (syst))%

  10. Helicity asymmetry in electron scattering where R’s are response functions and v’s are kinematics factors T. D. Donnelly and A. S. Raskin, Ann. Phys 169, 247 (1986)

  11. Ratio of asymmetries

  12. 3He inclusive response functions near quasi-elastic peak in PWIA Transverse- longitudinal: Transverse: where H’s are calculated by momentum distribution and nucleon polarization in 3He Proton: HpT’ Neutron: Hn Proton: HpTL’ A. Kievsky, E. Pace, G. Salme’ and M. Viviani, PRC 56 (1997) p.64

  13. 3He spin structure Spin-1/2 particle, 3 spin-1/2 nucleons (protons and neutron) Effective Neutron Target Angular Momentuml=0 l=0 l=2 ~90% ~1-2% ~8%

  14. The ratio of asymmetries as functions of form factors • By measuring ATL’/AT’ and using GEp, GMn, and GMn as known parameters can one extract GEn

  15. Final result of GEn at Q2=0.95 (GeV/c)2 • Results: • GEn/GD=0.226±0.041 (stat)±0.016 (syst) • GEn=0.0414±0.0077 (stat)±0.0032 (syst) • Conclusion • Our unprecedented method of measuring GEn(ratio of asymmetries in ) gave results in agreement with world data

  16. Comments and Outlook • Further theoretical support (near quasi-elastic peak) • Advantages: • Single arm (HRS) detector calibration • At higher Q2,GEn contributes more strongly to ATL’than the other form factors. • Big saving of beam time: 18% accuracy in 3-day run • Ratio-of-asymmetry method insensitive to systematic error (beam and target polarization, dilution factor, radiative correction partly cancel)

  17. Graduate Students G. Jin, University of Virginia E. Long, Kent State University M. Mihovilovič, Jožef Stefan Institute Y. Zhang, Lanzhou University Run Coordinators A. Camsonne, Jefferson Lab P. Monaghan, Hampton University S. Riordan, University of Virginia B. Sawatzky, Temple University R. Subedi, University of Virginia V. Sulkosky, MIT Y. Qiang, Duke University B. Zhao, College of William and Mary Thanks to the Hall A Quasi-Elastic Family Experiments Spokespersons T. Averett, College of William and Mary (E05-015, E08-05) J. P. Chen, Jefferson Lab (E05-015) S. Gilad, MIT (E05-102) D. Higinbotham, Jefferson Lab (E05-102, E08-005) X. Jiang, Rutgers University (E05-015) W. Korsch, University of Kentucky (E05-102) B. E. Norum, University of Virginia (E05-102) S. Sirca, University of Ljubljana (E05-102) V. Sulkosky, MIT (E08-005) E05-015, E08-005, and E05-102 Collaboration K. Allada B. Anderson J. R. M. Annand W. Boeglin P. Bradshaw M. Canan C. Chen R. De Leo X. Deng A. Deur C. Dutta L. El Fassi D. Flay F. Garibaldi H. Gao R. Gilman F. Salvatore M. Shabestari A. Shahinyan B. Shoenrock J. St. John A. Tobias W. Tireman G. M. Urciuoli D. Wang K. Wang J. Watson B. Wojtsekhowski Z. Ye X. Zhan X. Zheng L. Zhu S. Golge O. Hansen T. Holmstrom J. Huang H. Ibrahim E. Jensen M. Jones H. Kang J. Katich C. W. Kees P. King J. LeRose R. Lindgren H. Lu W. Luo P. Markowitz M. Meziane R. Michaels B. Moffit N. Muangma H. P. Khanal K. Pan D. Parno E. Piasetzky M. Posik A. J. R. Puckett X. Qian X. Qui A. Saha

  18. Four nucleon form factors J. J. Kelly, PRC 068202, 2004

  19. Ratio of Inclusive Asymmetry ATL’/AT’ Longitudinal: Transverse: Asymmetry ratio: Where v’s are kinematics factors • By measuring ATL’/AT’ and using GEp , GMn , GMn as known parameters can one extract GEn

  20. Asymmetry Results • Kinematics: • 3 pass beam, HRS-R 170, Q2=0.95 GeV2 • Analysis: • Asymmetry in 0.9<x<1.1 • Yawei Zhang’s target and dilution factor analysis • Karl Slifer’s radiative correction code radcor.f • Results: • ATL’=-0.55±0.09(stat)±0.04(syst)% • AT’ =3.12±0.10(stat)±0.21(syst)% • Error: • Stat error dominates ATL’ • Syst error contributed by beam and target polarization, and dilution factor

  21. Analysis on the ratio of asymmetries • Ratio: • ATL’/AT’ =-0.18±0.03(stat)±0.01(syst) • Statistical uncertainty dominates • Systematic • Beam polarization: <3% • Dilution factor cancels • Target polarization: ~0.6% contributed by the frequency reading Δνin EPR calibration • Radiative correction: <5%

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