Gravitational Form Factors: Experimental Status and Outlook

Gravitational form factors (GFFs) offer a unique probe of the internal structure of hadrons, encoding the distributions of mass, pressure, and shear. In the nucleon, they provide access to fundamental aspects of QCD dynamics, including the role of gluons in confinement and mass generation. I will review the current and future experimental program aimed at extracting GFFs, including near-threshold quarkonium production and deeply virtual Compton scattering.

New results from the J/ψ-007 experiment in Hall C, using the muon decay channel, double the available statistics and improve constraints on the gluonic pressure distribution. Together with earlier electron-channel results, these data support a picture in which quarks generate repulsive pressure at short distances, while gluons provide a stabilizing inward force at larger radii. Combined analyses of near-threshold data from Hall C and GlueX suggest that the scalar radius of the proton exceeds its charge and mass radii, raising questions about how to define the "size" of the proton.

Looking ahead, I will discuss future opportunities, including planned measurements to refine the quark and gluon GFFs, a novel program to extract the strangeness D-term via near-threshold φ electroproduction, and a brief outlook on SoLID at Jefferson Lab and the EIC.