Charge asymmetry for electron (positron)-proton elastic scattering at large angle

TL;DR

This paper investigates charge asymmetry in electron and positron elastic scattering off protons at large angles, analyzing the interference effects of different amplitudes and providing numerical estimates at high energies.

Contribution

It introduces a model separating proton and inelastic contributions to the box amplitude and argues for cancellation of strong interaction effects based on analyticity.

Findings

Charge asymmetry arises from interference of Born and box amplitudes.

Proton and inelastic contributions are separated and parametrized in the model.

Numerical estimates are provided for high-energy scattering.

Abstract

Charge asymmetry in electron (positron) scattering arises from the interference of the Born amplitude and the box-type amplitude corresponding to two virtual photons exchange. It can be extracted from electron proton and positron proton scattering experiments, in the same kinematical conditions. Considering the virtual photon Compton scattering tensor, which contributes to the box-type amplitude, we separate proton and inelastic contributions in the intermediate state and parametrize the proton form-factors as the sum of a pure QED term and a strong interaction term. Arguments based on analyticity are given in favor of cancellation of contributions from proton strong interaction form factors and of inelastic intermediate states in the box type amplitudes. In frame of this model, with a realistic expression for nucleon form-factors, numerical estimations are given for moderately high energies.