First measurement of near-threshold J/$\psi$ exclusive photoproduction off the proton

The GlueX Collaboration, A. Ali, M. Amaryan +132

We report on the measurement of the $\gamma p\to J/\psi p$ cross section from $E_{\gamma }=11.8$ GeV down to the threshold at $8.2$ GeV using a tagged photon beam with the GlueX experiment…