Two-loop coefficient function for DVCS: Vector contributions

TL;DR

This paper calculates the two-loop coefficient function for DVCS using conformal symmetry, providing an analytic expression and analyzing the size of the NNLO correction to the Compton form factor.

Contribution

It presents the first analytic two-loop coefficient function for vector DVCS contributions in the $ar{MS}$ scheme using conformal symmetry methods.

Findings

The NNLO correction to the Compton form factor is about 10% of the tree level.

The correction is roughly half the size of the NLO correction.

The analytic expression is valid in the $ar{MS}$ scheme for momentum fraction space.

Abstract

Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the vector flavor-nonsinglet contribution to deeply-virtual Compton scattering (DVCS). The analytic expression for the coefficient function in momentum fraction space is presented in the $\overline{\text{MS}}$ scheme. The corresponding next-to-next-to-leading order correction to the Compton form factor $\mathcal{H}$ for a simple model of the generalized parton distribution appears to be rather large: a factor two smaller than the next-to-leading order correction, approximately $\sim 10$\% of the tree level result in the bulk of the kinematic range, for $Q^2=4$ GeV$^2$.