Revisiting $J/\psi$ photoproduction at threshold

The study of $J/\psi$ photoproduction at low energies has consequences for the understanding of multiple aspects of nonperturbative QCD, ranging from mechanical properties of the proton, to the binding inside nuclei, and the existence of hidden-charm pentaquarks. A work by the JPAC collaboration, led by Daniel Winney (SCNU), Cesar Fernandez-Ramirez (UNED & UNAM), and Alessandro Pilloni (Messina), Adam Szczepaniak (Indiana U., PI), and Jinfeng Liao (Indiana U., co-PI), together with Astrid Hiller Blin (Tubingen), Miguel Albaladejo (IFIC Valencia), Lukasz Bibrzycki (AGH Krakow), N. Hammoud (INP Krakow graduate student),Vincent Mathieu (Barcelona U., co-PI), Gloria Montana (JLab), Robert Perry (Barcelona), Vanamali Shastry (Indiana), Wyatt Smith (IU graduate student), reanalyzes the latest photoproduction cross sections from GlueX and the $007-J/\psi$ experiments at Jefferson Lab. The results suggest a nonnegligible contribution from open charm intermediate states and an incompatibility with Vector Meson Dominance, which might affect the extraction of the gravitational form factor of the proton and needs to be properly understood. A wide array of physics possibilities that are still compatible with present data need to be disentangled.

Papers: Phys. Rev. D 108 (2023), 054018