Twist-three cross-sections in deeply virtual Compton scattering

TL;DR

This paper analyzes the contributions of twist-three effects in deeply virtual Compton scattering, comparing them with twist-two effects across various experimental kinematics, and justifies the leading-twist approximation used in prior studies.

Contribution

It provides explicit formulas for cross-sections including twist-three effects, estimates twist-three form factors using Wandzura-Wilczek relations, and discusses optimal kinematic regions for isolating leading-twist contributions.

Findings

Twist-three contributions are kinematically suppressed at JLab and EIC energies.

Leading-twist approximation is justified in typical experimental conditions.

Identifies kinematic regions where twist-three effects can be separated from twist-two effects.

Abstract

We study the deeply virtual Compton scattering process with both twist-two and twist-three Compton form factors and present our cross-sections formulas with all polarization configurations. While the twist-three contributions are generally assumed to be negligible in the literature due to the kinematical suppression, we compare them with the twist-two ones at typical JLab 6 GeV and 12 GeV kinematics as well as EIC kinematics and show their kinematical suppression explicitly, justifying the leading-twist approximation made in the literature. In addition, we also estimate the twist-three Compton form factors using Wandzura-Wilczek relations and inputs of twist-two generalized parton distributions based on a reggeized spectator model. With those estimated Compton form factors, we analyze the kinematical behavior of twist-two and twist-three cross-sections in a wide range of kinematics, and discuss the optimal regions for separating the leading-twist effects from the higher-twist ones.