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

TL;DR

This paper calculates the NNLO corrections to deeply-virtual Compton scattering, providing essential theoretical input for upcoming high-precision measurements at the Electron-Ion Collider.

Contribution

It presents the first two-loop NNLO coefficient functions for DVCS, crucial for accurate GPD extraction at high energies.

Findings

NNLO corrections significantly affect the imaginary part of $ ext{Re} \, extbf{H}$.

Large NNLO effects up to a factor of two at $Q^2=4$ GeV$^2$.

Cancellation between quark and gluon contributions influences correction size.

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.