Two Photon Exchange Contributions to Elastic e + p --> e + p Process in a Nonlocal Field Formalism

Abstract

We compute the two photon exchange contributions to elastic scattering of polarized electrons from target protons. We use a nonlocal field theory formalism for this calculation. The formalism maintains gauge invariance and provides a systematic procedure for making this calculation. The results depend on one unknown parameter \bar b. We compute the two photon exchange correction to the ratio of electric to magnetic form factors extracted using the polarization transfer experiments. The correction is found to be small if \bar b ~ 1. However for larger values of \bar b>3, the correction can be quite significant. The correction to the polarization transfer results goes in the right direction to explain their difference with the ratio measured by Rosenbluth separation method. We find that the difference between the two experimental results can be explained for a wide range of values of the parameter \bar b. We also find that the corrections due to two photon exchange depend on the photon longitudinal polarization epsilon. Hence we predict an epsilon dependence of the form factor ratio extracted using the polarization transfer technique. Finally we obtain a limit on \bar b by requiring that the non-linearity in epsilon dependence of the unpolarized reduced cross section is within experimental errors.

10 pages 7 figures

References in corpus (17)

• The ratio of proton's electric to magnetic form factors measured by polarization transfer
• Measurement of GEp/GMp in ep -> ep to Q2 = 5.6 GeV2
• Nucleon Electromagnetic Form Factors
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• Dispersion analysis of the nucleon form factors including meson continua
• Two-photon exchange in elastic electron-nucleon scattering
• Nucleon electromagnetic form factors
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• Model independent properties of two-photon exchange in elastic electron proton scattering
• Extraction of two-photon contributions to the proton form factors
• Radiative Corrections to Elastic Electron-Proton Scattering for Polarized Electrons
• Rosenbluth Nonlinearity from Two-Photon Exchange
• Two Photon Exchange Contributions to Elastic ep Scattering in the Nonlocal Field Formalism

Cited by in corpus (1)

• Gauge Invariant Two-Photon-Exchange Contributions in $e^{-}{\pi }^{+}\to e^{-}{\pi }^{+}$