Sub-threshold J/ψ and Υ production in γA collisions

We study sub-threshold heavy quarkonium (J/psi and Upsilon) photo-productions in gamma A collisions as an independent test of the universality of the nucleon-nucleon short range correlation (SRC) in nuclear scattering processes. Just below the gamma p threshold, the cross section is dominated by the mean field contribution of nucleons inside the nucleus. The SRC contributions start to dominate at lower photon energies, depending on the fraction of the SRC pairs in the target nucleus. We give an estimate of the cross sections in the sub-threshold region both for J/psi and Upsilon. This may be helpful for future measurements at JLab as well as at the Electron-Ion Collider in the U.S., and especially in China. (C) 2020 The Authors. Published by Elsevier B.V.