Two-photon exchange and polarization physics in electron-proton scattering

TL;DR

This paper investigates the effects of two-photon exchange in elastic electron-proton scattering, analyzing how it influences observables like spin asymmetries and cross-sections through phenomenological and theoretical approaches.

Contribution

It provides a model-independent analysis of experimental data on TPE effects and compares these results with theoretical calculations, enhancing understanding of TPE in scattering.

Findings

Imaginary part of TPE affects spin asymmetries

Real part of TPE influences scattering cross-sections

Phenomenological analysis aligns with theoretical models

Abstract

We discuss effects of two-photon exchange (TPE) in various observables of the elastic ep-scattering. The imaginary part of the TPE amplitude manifests in target and beam normal spin asymmetries. The real part contributes to the cross-section. A model-independent phenomenological analysis of experimental data is performed. Its results are compared with theoretical calculations.