Mechanical properties of the nucleon from the generalized parton distributions

TL;DR

This paper investigates the proton's internal mechanical structure by analyzing gravitational form factors derived from generalized parton distributions, revealing insights into energy, pressure, and shear force distributions within the nucleon.

Contribution

It introduces a model-based extraction of the D-term GFF from experimental data, providing new quantitative insights into the proton's internal stress and mechanical properties.

Findings

Determined the quark contribution to the D-term GFF of the proton.

Estimated the proton's mechanical and mass radii.

Mapped the internal pressure and shear force distributions.

Abstract

The proton's internal structure is characterized not only by its charge and magnetic distribution but also by its mechanical and mass properties, which are encoded in the energy-momentum tensor (EMT) of quantum chromodynamics (QCD). These properties provide insights into the spatial distributions of energy, pressure, and shear forces within the proton. Understanding the proton's internal structure, including properties such as its mechanical and mass radii, is essential for unraveling the complex interplay between quarks and gluons that govern its stability and dynamics. In this study, we investigate the gravitational form factors (GFFs) of the proton, particularly the D-term, which encodes key information about the internal stress distribution, pressure, and shear forces within the nucleon. Using a model for skewness-dependent generalized parton distributions constructed from the double-distribution representation, we extract the quark contribution to the $ D(t) $ GFF of the EMT by analyzing available data on Compton form factors. We then employ this extracted GFF to explore the mechanical properties of the proton, including its mechanical and mass radii, as well as the internal pressure and shear force distributions. Our results provide new insights into the proton's internal structure and contribute to the broader understanding of nucleon properties.