Near-threshold heavy quarkonium photoproduction in a light-front spectator model

The near-threshold photo- and electroproduction of heavy vector quarkonia off the proton provides direct access to its gluonic structure. In particular, the cross section for $J/\Psi$ photoproduction near threshold is governed by the proton's gluon gravitational form factors (GFFs). In this work, we employ the generalized parton distribution framework together with gluon GFFs calculated in a light-front gluon-spectator model inspired by soft-wall AdS/QCD to predict both the differential and total cross sections for near-threshold $J/\Psi$ and $\Upsilon$ photoproductions. Our results for $J/\Psi$ photoproduction show good agreement with recent experimental data from the $J/\Psi$-007 and GlueX Collaborations at Jefferson Lab, as well as with earlier measurements from SLAC and Cornell.