Observation of strong nuclear suppression in exclusive $J/\ddot{I}ˆ$ photoproduction in Au$+$Au ultra-peripheral collisions at RHIC

STAR Collaboration

We report a measurement of exclusive $J/\ddot{I}ˆ$ photoproduction in Au$+$Au ultra-peripheral collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV using the STAR detector. For the first time,…