Search for Effects Beyond the Born Approximation in Polarization Transfer Observables in Elastic Scattering
Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, G{sub E}/G{sub M}, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H({rvec e}, e' {rvec p}) reaction for three different beam energies at a Q{sup 2} = 2.5 GeV{sup 2}, spanning a wide range of the kinematic parameter {epsilon}. The ratio R, which equals {mu}{sub p}G{sub E}/G{sub M} in the Born approximation, is found to be independent of {epsilon} at the 1.5% level. The {epsilon} dependence of the longitudinal polarization transfer component P{sub {ell}} shows an enhancement of (2.3 {+-} 0.6)% relative to the Born approximation at large {epsilon}.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); Italian Inst. for Nuclear Research; CEA; CNRS
- Contributing Organization:
- GEp2γ Collaboration
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1020659
- Report Number(s):
- ANL/PHY/JA-68098; PRLTAO; TRN: US1103755
- Journal Information:
- Physical Review Letters, Vol. 106, Issue 13; ISSN 0031-9007
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- ENGLISH
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