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Transverse Asymmetries from Nuclei

Explore measurements of A_T transverse asymmetry in few-GeV electron scattering on nuclei (H, 4He, 12C, 208Pb) at Jefferson Lab. Investigate systematic errors for PREX, nuclear structure probe, and predictions for elastic and inelastic intermediates.

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Transverse Asymmetries from Nuclei

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  1. Robert Michaels Jefferson Lab on behalf of the HAPPEX Collaboration Transverse Asymmetries from Nuclei Measurements at Jefferson Lab of the transverse asymmetry A T in few-GeV elastic electron scattering at forward angles from various nuclei : H, 4He, 12C, 208Pb New --PREX Expt 2010

  2. Hall A Hall A at Jefferson Lab High Resolution Spectrometers (HRS)

  3. Detector Package in HRS PREX Integrating Detectors UMass / Smith DETECTORS

  4. Lead / Diamond Target Diamond LEAD • Three bays • Lead (0.5 mm) sandwiched by diamond (0.15 mm) • Liquid He cooling (30 Watts) 50

  5. y AT > 0 means - x + z Beam-Normal Asymmetry in elastic electron scattering i.e. spin transverse to scattering plane We measured this, in part, because it is a possible systematic error for PREX. New results from PREX (syst) (stat)

  6. RightHRS 12 C Left HRS 12 C Left HRS 208Pb Right HRS 208Pb Left + Right HRS 208Pb Signs flip between Left and Right HRS (good !) Combined 208Pb is small  small syst. error for PREX

  7. “elastic” “inelastic” Interest in A T A Tis T-odd, P-even • As a radiative correction, it is similar to other T-odd QED FSI that obscure measurements of nuclear g-decay, neutron b-decay, or other searches for T-odd, P-even interactions. Probe of nucleon structure • Doubly virtual Compton scattering (VVCS) constrains interpretation from DVCS Dominated by spectrum of hadronic intermediate states • Provides a clear and accessible window on the treatment of hadronic intermediate states in box diagrams. GE/GM is influenced by the real part of 2-g amplitude. A Tis generated from the imaginary part of the 2-g amplitude.

  8. Predictions for 208Pb elastic intermediate only E.D. Cooper, C. J. Horowitz, Phys. Rev. C72 : 034602 (2004) A ~ - 0.4 ppm Include inelastic intermediate A.V. Afanasev arXiv:0711.3065v2 [hep-ph] (Nov, 2007) A ~ - 5 ppm Include inelastic intermediate M. Gorchtein, C. J. Horowitz, Phys. Rev. C77 : 044606 (2008) A ~ - 4.5 ppm

  9. Predictions for 12C For 12C I didn’t see any publications but C. J. Horowitz tells me it should be similar magnitude and same sign as 4 He. I believe A. V. Afanasev agrees with this.  Expect “About -5 ppm “ Our data at E = 1.063,

  10. Earlier Work: for 4He e.g. A.V. Afanasev, N.P. Merenkov , Phys. Rev. D70 : 073002 (2004) With inelastic states, A ~ 10-5 at 6 degrees, 3 GeV HAPPEX 2004 Without inelastic states, A ~ 10-9

  11. Summary : A T from NucleiElastic Scattering HAPPEX 2004 - 5 PREX 2010 Error: quadratic sum of stat & syst

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