Off-forward gluonometry

TL;DR

The paper addresses accessing the gluonic content of hadrons through tensor gluon skewed parton distributions in deeply virtual Compton scattering, leveraging a spin-2 gluon operator that decouples from quarks. It provides a comprehensive set of results: the NLO coefficient function for DVCS on tensor gluons, two-loop anomalous dimensions including diagonal and non-diagonal parts, and the exclusive ER-BL evolution kernel necessary for proper scale evolution. It also proposes weighted cross sections (cos(3φ_r) and sin(3φ_r) asymmetries) to extract the real and imaginary parts of tensor gluon amplitudes from experiment, accounting for interference with the Bethe–Heitler process. Altogether, this work completes the NLO toolkit for studying scaling violations of tensor-gluon SPDs in DVCS and lays out concrete observables for experimental access.

Abstract

We explore the deeply virtual Compton scattering process at NLO with the emphasis on the measurement of the tensor gluon skewed distributions. We recalculate the one-loop coefficient function and give two-loop results for anomalous dimensions and exclusive evolution kernels required for studying the logarithmic scaling violation. We evaluate weighted cross sections which give direct access to these functions on experiment.

Figures (3)

• Figure 1: One-loop diagrams for the coefficient function.
• Figure 2: Input SPD in (a) and its evolved shape at $4 {\rm GeV}^2$ in (b) and at $100\ {\rm GeV}^2$ in (c) for $N_{\rm max} = 100$.
• Figure 3: 1PI Green function for calculation of the renormalization constant $Z^-_A$.