Search for two photon exchange from e++e−→p+p¯+γ data

We look for asymmetries in the angular distributions of events from recent data on e++e−→p+p¯+γ 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%. Such error is of the order of the asymmetry expected from radiative corrections as calculated from QED. 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.