Probing the gluonic gravitational form factors of the proton using near-threshold J/Ψ photoproduction.

Measurements of near threshold quarkonia photoproduction cross sections provides a unique probe of gluons inside the nucleon, hence allowing the extraction of its gluonic form factors and mass structure. Experiments conducted in Hall C ((E12-16-007), Hall B (E12-12-001, E12-12-001A, E12-11-003B) and Hall D (GlueX) at Jefferson Lab, measured  J/Ψ differential cross sections as a function of photon energy E_γ and Mandelstam variable t (momentum transfer from initial photon to the produced J/Ψ) in the threshold region. These two dimensional cross section results from Hall C J/Ψ-007 ¹ and Hall D GlueX ^2,3 experiments were published recently. The results are from the e^-e⁺ decay channel of the produced J/Ψ. We will present new results from the μ^-μ⁺ channel in the case of the Hall C J/Ψ-007 experiment. Together with the published results we will explore their impact on our knowledge of the proton’s gluonic mechanical properties due to the improved total statistical uncertainty.

[1] Nature 615, 813–816 (2023)

[2] Phys. Rev. Lett. 123, 072001 (2019)

[3] arXiv:2304.03845v2 (2023)