"Rosenbluth" separation of the $J/\psi $ near-threshold photoproduction -- an access to the gluon Gravitational Form Factors at high $t$

TL;DR

This paper introduces a method to extract the proton's gluon gravitational form factors at high momentum transfer by analyzing near-threshold J/psi photoproduction data using Rosenbluth-like separation techniques, comparing results with lattice calculations.

Contribution

It presents a novel approach to separate and analyze the gluon gravitational form factors from experimental data using GPD and holographic models, extending the analysis to high momentum transfer regions.

Findings

Demonstrates the feasibility of extracting gGFFs at high t.

Shows consistency with lattice calculations in the overlapping region.

Highlights the need for higher statistics for precise validation.

Abstract

We perform analysis of the near-threshold $J/\psi $ photoproduction data off the proton based on two theoretical approaches, GPD [1] and holographic [2], that represent the differential cross sections as powers of the skewness parameter with coefficients that depend only on the momentum transfer $t$. This allows to separate kinematically the corresponding coefficient functions, in much the same way as this is done for the electric and magnetic form factors using the Rosenbluth separation. We examine the independence of the extracted functions with the photon beam energy. These functions, under additional assumptions, are related to the proton's gluon Gravitational Form Factors (gGFFs). We compare the extracted functions with lattice calculations of the gGFFs in the region of $0.5<|t|<2$~GeV$^{2}$, where they overlap. Such analysis demonstrates the possibility of extracting some combinations of the gGFFs from the data at high $t$, complementary to the lattice calculations available in the low $t$ region. However, higher statistics are needed to more accurately check the predicted scaling behavior of the data and compare with the lattice results, thus testing and comparing the theoretical assumptions used in the GPD and holographic models.