Gluonic Energy Momentum Tensor Form Factors of the Proton

TL;DR

This paper reports on measurements of gluonic gravitational form factors of the proton through near-threshold J/psi photoproduction, using holographic QCD to interpret the results and discuss future experimental prospects.

Contribution

It introduces a novel method to extract gluonic gravitational form factors from near-threshold J/psi photoproduction data, advancing understanding of gluon dynamics in the proton.

Findings

Extraction of gluonic gravitational form factors from experimental data

Holographic QCD framework applied to interpret threshold behavior

Implications for future experiments at Jefferson Lab and Electron-Ion Collider

Abstract

Gravitational form factors (GFFs), defined through the matrix elements of the energy-momentum tensor, provide critical insights into the internal structure of nucleons and nuclei. In particular, their Fourier transforms -- evaluated in the Breit frame -- reveal spatial distributions of mass, pressure, and shear force densities associated with both quark and gluon constituents. This work presents recent measurements of near-threshold $J/\psi$ photoproduction on the proton, performed in Hall C at Jefferson Lab, utilizing data from the electronic decay channels of the $J/\psi$. These results enable the extraction of gluonic gravitational form factors (gGFFs), offering a novel probe of the gluon dynamics within the nucleon. The analysis employs a holographic QCD framework to interpret the threshold behavior of the cross sections and to facilitate the extraction of the gGFFs. The implications of these measurements are discussed in the context of upcoming experimental programs, including the near-threshold electro- and photoproduction studies with SoLID at Jefferson Lab and the $\Upsilon$ production program at the Electron-Ion Collider using the ePIC detector. These future efforts are expected to significantly improve the precision of gGFF determinations and provide essential tests of their universality across different kinematic regimes.