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Precision Measurement of R L and R T of Quasi-Elastic Electron Scattering

Precision Measurement of R L and R T of Quasi-Elastic Electron Scattering In the Momentum Transfer Range 0.55GeV/c ≤|q|≤1.0GeV/c *. Yan Xinhu. Department of Modern Physics of USTC. 2008/04/28. * Supported by the National Natural Science Foundation of China(10605022)

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Precision Measurement of R L and R T of Quasi-Elastic Electron Scattering

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  1. Precision Measurement of RL and RT of Quasi-Elastic Electron Scattering In the Momentum Transfer Range 0.55GeV/c≤|q|≤1.0GeV/c* Yan Xinhu Department of Modern Physics of USTC 2008/04/28 *Supported by the National Natural Science Foundation of China(10605022) and Natural Science Foundation of Anhui Educational Committee(KJ2007B028) 国家自然科学基金子

  2. Outline 1.Introduction ２.CSR Experiment (E05-110) at JLab ３.Summary

  3. 1.Introduction Motivation: How can we connect the low energy theories and high Energy theory (QCD) ? How nucleon properties are affected by the nuclear medium?

  4. One photon exchange assumption , inclusive electron scattering • Response Functions • Coulomb Sum 2 T. de Forest, Jr., Nucl. Phys. A414 (1984) 347.

  5. Saturation/Deviation of Coulomb Sum Rule Saturation of the Coulomb Sum at the sufficiently large q Deviation of the Coulomb Sum at small q Pauli blocking Nucleon-nucleon long-range Correlation at large q (>>2KF)‏ Short-range correlation ~10% Modification of the free nucleon electromagnetic propertiesinside the nuclear medium One of the long lasting question in nuclear physics

  6. Overview Comprehensive measurements of the Coulomb sum at various labs for over 20 years Limited range in q and  At Bates(MIT) and Saclay(France) q550MeV/c At SLAC(Stanford) q=1140MeV/c CSR experiment ( E05-110) at JLab Covers a region 550MeV/cq1000MeV/c

  7. Previous Measurements For the past twenty years, a large experimental program at Bates, Saclay and SLAC Limited kinematic coverage in q and  due to machine limitations

  8. Controversy on CSR Early data shows significant quenching of the CSR With the addition of forward angle data, Bates claims nosignificant quenching Saclay new analysis claims that quenching persists SL (q)‏

  9. ２.CSR Experiment (E05-110) at JLab Commissioned in early 1990s first experiment in 1994 High luminorsity electron beam:1039cm-2s-1 High density target Maximum current 200 μA The gain of each linac is adjustable 400MeV-500MeV, Maximum Energy 5.7GeV

  10. JLab Hall A

  11. Hall A Beamline and Spectrometers NaI ARC: beam momentum BCM: Beam Charge eP: Beam energy Compoton Polarimetry& Moller Polarimetry: beam polarization Raster & BPM: beam position

  12. Momentum Range 0.3 – 5.7 GeV/c Configuration QQDQ Bend Angle 45o Optical Length 23.4 m Momentum Acceptance +/- 4.5% Dispersion (D) 12.4 m Momentum Resolution (FWHM) 1 x 10-4 Angular Acceptance: HorizontalVertical +/- 30 mr+/- 60 mr Solid Angle: 6 msr Angular Resolution: (FWHM)HorizontalVertical 0.5 mr1.0 mr Transverse Length AcceptanceTransverse Position Resolution (FWHM) +/- 5 cm1 mm Parameters of HRS

  13. Installation of NaI detector

  14. Performance ~3% at 1GeV Or ~9% at 0.1GeV

  15. CSR Experiment at JLab (Hall A)‏ Scattering Angles15°,60°,90°,120° compromise between counting rates and lowest Momentum setting two more angles at 60°90°, equally spaced ε─ improved systematic uncertainties Beam Energy0.4 to 4.0GeV Range ofq~550MeV/c to 1000MeV/c Targets4He, 12C, 56Fe , 208Pb Study A or density dependent effect Study of Coulomb corrections (small for 4He or 12C, but large for 208Pb) Scattered Energy covers complete range of QE peak and beyond

  16. Coverage at 15°

  17. Coverage at 60°

  18. Coverage at 90°

  19. Coverage at 120°

  20. Kinematic Coverage

  21. Separation of RL and RT forward angle (f)‏ backward angle (b)‏

  22. Estimation of Accuracy of RL and RT Ratio of longitudinal and transverse virtual photo-absorption cross section At JLab Previous Experiment

  23. Kinematic Coverage in ε versus 

  24. Preliminary Results

  25. Preliminary Results

  26. Expected

  27. Coulomb Correction Need to take into account the effect of the nucleus Coulomb field to the incoming/outgoing electrons Approximate corrections via EMA Full treatment of Coulomb corrections viaDWBA Up to now, some disagreement between EMA & DWBA What to do ,then? Whatever is the best way for corrections

  28. Comparison of Various Methods

  29. 3.Summary Experiment in smooth progress Completed by Jan. 2008 A few new features High enough momentum transfer, previously unexplored. Independent energy measurement forbackground reduction Hope to answer the question on the CSR

  30. Thanks

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