Determination of the pion generalized parton distributions at zero skewness

TL;DR

This paper performs a comprehensive analysis of pion generalized parton distributions at zero skewness by fitting experimental form factor data using various pion PDFs, resulting in a consistent GPD set that aligns well with measurements.

Contribution

It introduces a novel global QCD analysis method to extract pion GPDs at zero skewness using multiple PDF sets and a minimal parameter profile function, enhancing understanding of pion structure.

Findings

Valence pion GPDs have similar x-dependence across analyses

The MAP23 PDF set yields the best fit to data

Predicted form factors agree well with experimental measurements

Abstract

We perform a global QCD analysis of the pion electromagnetic form factor (FF) data from pion electroproduction and elastic pion scattering to extract the valence pion generalized parton distributions (GPDs) at zero skewness. The analysis uses three different sets of pion parton distribution functions (PDFs), namely xFitter, JAM21, and MAP23, to construct the GPD ansatz. Through a $\chi^2$ minimization and a careful parametrization scan, we determine the profile function parameters and find that only two parameters are sufficient to describe the data. The extracted valence pion GPDs from different analyses have similar $x$-dependence, with minor differences at small momentum transfer. The resulting theoretical predictions for the pion electromagnetic FF and its squared magnitude show good agreement with experimental measurements. Among the three analyses, the one using the MAP23 PDFs provides the best overall fit and is adopted as the final GPD set. Our results offer a consistent determination of the valence pion GPDs, indicating a minor impact of the choice of pion PDFs. The present study provides a solid foundation for future investigations of pion structure, including its charge radius, tomography, and mechanical properties.