Leading-order QED radiative corrections to timelike Compton scattering on the proton

Abstract

We evaluate the leading-order QED radiative corrections to the timelike Compton scattering (TCS) process $\gamma p\to l^{-}{l}^{+}p$. 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 di-lepton 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 parameterizations for a recent CLAS12@JLab TCS experiment.

16 pages, 13 figures

References in corpus (6)

• Unitary Isobar Model - MAID2007
• High-precision determination of the electric and magnetic form factors of the proton
• Electromagnetic excitation of the Delta(1232)-resonance
• The Proton Radius Puzzle
• Dispersive evaluation of the D-term form factor in deeply virtual Compton scattering
• Tomographic image of the proton

Cited by in corpus (1)

• Soft-photon radiative corrections to the $e^{-}p\to e^{-}p{l}^{-}{l}^{+}$ process