Soft-photon corrections to the Bethe-Heitler process in the $\gamma p\rightarrow l^+l^-p$ reaction

TL;DR

This paper calculates first-order QED radiative corrections in the soft-photon approximation for the gamma p to lepton pair production process, essential for upcoming lepton universality tests at MAMI.

Contribution

It introduces the first calculation of soft-photon QED corrections including finite lepton mass effects for this process.

Findings

Corrections are at the percent level for muons.

Corrections are around 10% for electrons.

Provides necessary theoretical input for upcoming experiments.

Abstract

We report on the calculation of first-order QED corrections for the $\gamma p\rightarrow l^+l^-p^{\prime}$ process. An upcoming experiment at MAMI (Mainz) aims to compare the cross sections of muon- and electron-pair production in this reaction to test lepton universality. Precise knowledge of the electromagnetic radiative corrections is needed for these measurements. As a first step, we present the leading QED radiative corrections in the soft-photon approximation when accounting for the finite lepton mass. For the kinematics at MAMI, we find corrections of the percent level for muons, and of order $10\%$ for electrons.