Accessing the Nucleon's Gravitational Structure through Near-Threshold Quarkonium Photoproduction
by
Zoom
Abstract:
The energy–momentum tensor (EMT) provides a fundamental and gauge-invariant description of how energy, momentum, and internal forces are distributed within hadrons. Its matrix elements define the gravitational form factors (GFFs), which encode the underlying partonic dynamics by revealing the mass decomposition of the nucleon, the spatial distributions of pressure and shear forces, and the angular momentum carried by quarks and gluons. As such, the study of GFFs has emerged as a central and timely topic in contemporary QCD hadron physics.
In this talk, I will focus on near-threshold photoproduction of heavy quarkonium as a clean and sensitive probe of the nucleon's gravitational structure. In this regime, the amplitude is dominated by gluonic dynamics and is directly related to matrix elements of the QCD EMT, enabling access to gluonic GFFs. The analysis is formulated within the framework of the QCD factorization framework for GPDs, which provides a systematic separation between short-distance dynamics and the non-perturbative nucleon matrix elements.
Finally, I will discuss the experimental prospects for accessing nucleon gravitational form factors through near-threshold quarkonium photoproduction at facilities such as Jefferson Lab and the future Electron–Ion Collider, and the implications for our understanding of the nucleon's internal structure.
About the speaker:
Bheemsehan Gurjar obtained his PhD in 2024 in the Department of Physics at the Indian Institute of Technology Kanpur, India. He subsequently held a postdoctoral position at IIT Kanpur from 2024 to 2025 under the Fellowship for Academic and Research Excellence. He is currently a postdoctoral researcher at the University of Science and Technology of China (USTC). He was awarded the Gary McCartor Award by the International Light Cone Advisory Committee at Light Cone 2023, held in Rio de Janeiro.
Zoom link: TBD