Search for two photon exchange from $e^+ +e^-\to p+\bar p +\gamma$ data

TL;DR

This study searches for two-photon exchange effects in $e^+ e^- o p ar{p} \gamma$ data by analyzing angular asymmetries, finding no evidence of such effects within a 2% error margin, consistent with a structureless proton model.

Contribution

First analysis of angular asymmetries in $e^+ e^- o p ar{p} \\gamma$ data to search for two-photon exchange effects, providing experimental constraints.

Findings

No asymmetry detected within 2% error margin.

Results consistent with a structureless proton model.

No evidence of two-photon exchange effects in the data.

Abstract

We look for asymmetries in the angular distributions of events from recent data on $e^+ +e^-\to p +\bar p +\gamma$ from BABAR collaboration. From first principles, as the C-invariance of the electromagnetic interaction and the crossing symmetry, the presence of two-photon exchange would create a forward backward asymmetry in the data. The analysis of the available data shows no asymmetry, within an error of 2%. This result is consistent with a structureless model for the proton, based on a calculation of $e^+ +e^-\to \mu^+ + \mu^- +\gamma$ with a proper replacement of the muon mass. As no systematic deviations are seen, we can conclude that these data do not give any hint of the presence of the two photon contribution, in all the considered kinematical range.