Leading-order QED Radiative Corrections to Timelike Compton Scattering on the Proton

We evaluate the leading-order QED radiative corrections to the timelike Compton scattering (TCS) process gamma p -> l(-) l(+) p. We study these corrections in two energy regimes using different models for the TCS amplitude. In the low-energy regime we calculate the contribution due to the proton and its lowest-energy excitation, the Delta(1232) resonance. In the high-energy near-forward kinematical regime we calculate the TCS amplitude in a handbag approach in terms of generalized parton distributions (GPDs). On the level of cross sections we find the QED radiative corrections to be in the 5%-10% range in the low-energy regime and around 20% in the high-energy regime. We show that in both the dilepton forward-backward asymmetry as well as in the photon beam helicity asymmetry these corrections nearly cancel out, making them gold-plated observables to extract the real and imaginary parts of the TCS amplitude. We demonstrate in particular the sensitivity of these asymmetries on GPD parametrizations for a recent CLAS12@JLab TCS experiment.