Higher-Order Kinematical Effects in Deeply Virtual Compton Scattering

TL;DR

This paper investigates how different choices of light-cone vectors and gauges influence higher-order kinematical corrections in deeply virtual Compton scattering, impacting the extraction of Compton form factors.

Contribution

It systematically analyzes the light-cone dependence of higher-twist corrections in DVCS cross-sections, clarifying their role as systematic uncertainties and guiding higher-order form factor reconstruction.

Findings

Light-cone choices affect twist-three kinematic corrections.

Kinematical corrections from higher-twist GPDs can remove light-cone dependence.

Systematic uncertainties are identified for JLab and EIC kinematics.

Abstract

We study the deeply virtual Compton scattering cross-section in twist-two generalized parton distribution (GPD) approximation, and show that different choices of light-cone vectors and gauges for the final photon polarization will lead to different higher-order kinematical corrections to the cross-section formula. The choice of light-cone vectors affects kinematic corrections at the twist-three level, accounting for the differences between the cross-section formulas in the literature. On the other hand, kinematical corrections from higher-twist GPDs should eliminate the light-cone dependence at twist three. Those light-cone dependencies are studied systematically at JLab 12 GeV and future EIC kinematics. They serve as the intrinsic systematic uncertainties in extracting the Compton form factors through the cross-section formula. More importantly, they are also necessary for understanding cross-section measurements with higher-twist precision and to reconstruct higher-order Compton form factors.