Generalized parton distributions at zero skewness

TL;DR

This paper provides a comprehensive analysis of generalized parton distributions at zero skewness by integrating diverse experimental data, revealing tensions between datasets, and offering new constraints on GPDs with implications for nucleon structure understanding.

Contribution

It introduces the first simultaneous analysis of all available data for GPDs at zero skewness, including sea-quark contributions, and explores tensions between datasets affecting GPD determinations.

Findings

WACS and $ G_M^p $ data impose new constraints on GPDs.

Significant tension exists between WACS and $ G_M^p $ data at high $ -t $.

Results for gravitational FF $ M_2 $ and $ J^p $ align with QCD predictions when including sea-quarks.

Abstract

We present a new determination of the generalized parton distributions (GPDs) with their uncertainties at zero skewness, $ \xi =0 $, through a simultaneous analysis of all available experimental data of the nucleon electromagnetic form factors (FFs), nucleon charge and magnetic radii, proton axial FFs (AFFs) and wide-angle Compton scattering (WACS) cross sections for the first time, and we investigate whether there is any tension between these data. This can be considered the most comprehensive analysis of GPDs at $ \xi=0 $ performed so far. We show that such an analysis provides the simultaneous determination of three kinds of GPDs, namely $ H^q $, $ \widetilde{H}^q $ and $ E^q $, considering also the sea-quark contributions. As a result, we find that the inclusion of the WACS and AFF data at larger values of the momentum transfer squared $ Q^2=-t $ can put new constraints on GPDs and change them drastically in some cases. We show that there is a considerable tension between the WACS and the proton magnetic form factor ($ G_M^p $) data, especially at larger values of $ -t $. However, we indicate that the results for the gravitational FF $ M_2 $ and the proton total angular momentum $ J^p $ calculated using the extracted GPDs are in relatively good agreement with the light-cone QCD sum rules (LCSRs) and lattice QCD predictions when the sea-quark contributions are considered and both WACS and $ G_M^p $ data are included in the analyses simultaneously.