# Updated analysis of recent results on electron and positron elastic scattering on proton

## TL;DR

This paper reviews recent experimental data on electron and positron elastic scattering on protons, comparing it with theoretical predictions including two-photon exchange, and finds no significant evidence of large two-photon contributions beyond expected levels.

## Contribution

It provides an updated analysis of experimental results on charge asymmetry in elastic scattering, confirming no substantial deviation from the Born approximation within current measurement precision.

## Key findings

- No evidence of enhanced two-photon exchange beyond expected levels
- Experimental data do not show significant charge asymmetry
- Results support the validity of the Born approximation at current precision

## Abstract

We discuss recent experimental results concerning the cross section ratio of positron over electron elastic scattering on protons, and compare with the predictions of a pre-existent calculation. The deviation from unity of this ratio, $i.e.$, a charge asymmetry different from zero, is the signature of contributions beyond the Born approximation. After reviewing the published results, we compare the elastic data to a calculation which includes the diagram corresponding to two-photon exchange. It turns out that all the data on the cross section ratio, in the limit of their precision, do not show evidence of enhanced two-photon contribution beyond the expected percent level. Our results confirm that experimental evidence for a large contribution of two-photon exchange is not yet found.