Orateur
Description
Incoherent $\rm{J/\psi}$ photoproduction is sensitive to fluctuations of the gluonic structure of the target. Thus, the measurement of $\rm{J/\psi}$ photoproduction off the colliding hadron sheds light on the initial state of QCD and provides important constraints on the initial conditions used in hydrodynamical models of heavy ion collisions. In this talk, we present the first measurement of the transverse momentum dependence of both coherent and incoherent $\rm{J/\psi}$ photoproduction in ultra-peripheral Pb–Pb collisions at mid-rapidity. These new results provide, for the first time, a clear indication of sub-nucleonic fluctuations of the lead target. We will also show recent results on the energy dependence of $\rm{J/\psi}$ photoproduction with proton dissociation in p–Pb collisions, measured for the first time at a hadron collider, which represent a first step towards probing fluctuations in the sub-nucleonic structure of the proton.
