  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.

High Energy Physics - Phenomenology;Nuclear Experiment;Nuclear Theory