From hard exclusive meson electroproduction to deeply virtual Compton scattering

TL;DR

This paper evaluates the universality of Generalized Parton Distributions by comparing theoretical predictions of deeply virtual Compton scattering with experimental data across various experiments, confirming the GPD framework's validity.

Contribution

It provides a comprehensive analysis of GPDs in hard exclusive processes, incorporating leading-twist calculations and experimental constraints, and offers predictions for future experiments.

Findings

Good agreement between GPD-based predictions and experimental data

Validation of GPD universality across multiple experiments

Predictions for upcoming JLab and COMPASS measurements

Abstract

We systematically evaluate observables for hard exclusive electroproduction of real photons and compare them to experiment using a set of Generalized Parton Distributions (GPDs) whose parameters are constrained by Deeply Virtual Meson Production data, nucleon form factors and parton distributions. The Deeply Virtual Compton Scattering amplitudes are calculated to leading-twist accuracy and leading order in QCD perturbation theory while the leptonic tensor is treated exactly, without any approximation. This study constitutes a check of the universality of the GPDs. We summarize all relevant details on the parametrizations of the GPDs and describe its use in the handbag approach of the aforementioned hard scattering processes. We observe a good agreement between predictions and measurements of deeply virtual Compton scattering on a wide kinematic range, including most data from H1, ZEUS, HERMES, Hall A and CLAS collaborations for unpolarized and polarized targets when available. We also give predictions relevant for future experiments at COMPASS and JLab after the 12 GeV upgrade.