We perform analysis of the near-threshold $J/\psi$ photoproduction data off the proton based on two theoretical approaches, generalized parton distribution (GPD) [Phys. Rev. D 109, 014014 (2024)] and holographic [Phys. Rev. D 106, 086004 (2022)], that represent the differential cross sections as powers of the skewness parameter with coefficients that depend only on the momentum transfer $t$. This allows us 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 of 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 $0.5<|t|<2{\mathrm{GeV}}^2$, 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.

Close

PrevNext

View figure in article

• Photon production
• Heavy mesons
• Form factors