Gluonic gravitational form factors of the proton

Zein-Eddine Meziani
Nuclear Experiment, Nuclear Experiment (nucl-ex)
2024-03-13 00:00:00
The gravitational form factors (GFFs) are a fundamental and elegant way to describe the structure of nucleons and nuclei. Their Fourier transform allows a description of the spatial distribution of the mass, angular momentum, pressure, and shear force densities for both quarks and gluons in the nucleon. While previous investigations predominantly focused on the proton electromagnetic form factors (EMFFs) leading to the charge and magnetization distributions determination, the current emphasis has shifted towards expanding our understanding of the gravitational form factors of quarks and gluons where little is known. In particular, more recently, the proton {\it gluonic} GFFs have been the target of an intensive investigation at Jefferson Lab. This endeavor, is not without its challenges, particularly in navigating the complexities associated with the near-threshold region. Nevertheless, it provides a bedrock for future nucleon and nuclei gluonic structure studies at the future EIC. In this talk, I will focus on the recent results of $J/\psi$ photoproduction near-threshold on the proton at Jefferson Lab to determine, in particular, the elusive {\it gluonic} gravitational form factors. We discuss the caveats of their extraction in the threshold region and mention the complementary measurements of $\Upsilon$ at the EIC critical to access the trace anomaly and gain insight into the origin of the nucleon mass.
PDF: Gluonic gravitational form factors of the proton.pdf
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