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arXiv · 2012.09565

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

Matthias Heller·Niklas Keil·Marc Vanderhaeghen
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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.

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Matthias Heller, Niklas Keil, Marc Vanderhaeghen. 2020-12-17. Leading-order QED radiative corrections to timelike Compton scattering on the proton. https://doi.org/10.1103/physrevd.103.036009

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