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

Abstract

We report on the calculation of first-order QED corrections for the $\gamma p\to l^{+}{l}^{-}{p}^{\prime }$ 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.

Comments: 23 pages, 10 figures, fixed typo in Eqs 64 and 66, minor corrections in text and figures, Version published in Phys. Rev. D