Deeply-virtual Compton scattering at the next-to-next-to-leading order

Abstract

Deeply-virtual Compton scattering gives access to the generalized parton distributions that encode the information on the transverse position of quarks and gluons in the proton in dependence in their longitudinal momentum. In anticipation of the high-precision experimental data in a broad kinematic range from the Electron-Ion Collider, we have calculated the two-loop, next-to-next-to-leading (NNLO) DVCS coefficient functions associated with the dominant Compton form factors $\mathcal H$ and $\mathcal E$ at large energies. The NNLO correction to the imaginary part of $\mathcal H$ appears to be rather large, up to factor two at the input scale $Q^2=4$ GeV$^2$ for simple GPD models, due to a cancellation between quark and gluon contributions.