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Mechanical properties of the nucleon from the generalized parton distributions

Muhammad Goharipour1,2,*, Hadi Hashamipour3, H. Fatehi4, Fatemeh Irani4, K. Azizi4,5,2, and S. V. Goloskokov6 (MMGPDs Collaboration)

  • *Contact author: muhammad.goharipour@ipm.ir
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Phys. Rev. D 112, 014016 – Published 8 July, 2025

DOI: https://doi.org/10.1103/jkhv-6949

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.

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Phys. Rev. D 112, 014016– Published 8 July, 2025
  • Received 27 January 2025
  • Accepted 23 June 2025
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