The strong electromagnetic fields generated by ultra-relativistic heavy ions provide the possibility to study photon-induced processes at the LHC in new kinematic regions. ALICE has measured the coherent photoproduction of J/ψ in Pb–Pb and p–Pb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. These collisions correspond to photon–proton and photon–Pb interactions, respectively. In these cases, the mass of the charm quark allows for perturbative QCD computations addressing the phenomena of saturation and nuclear shadowing, thus the study of such collisions provides information about the initial state of hadrons.
The evolution of the exclusive J/ψ photoproduction cross section off protons is measured with p–Pb data. The new Pb–Pb data from LHC Run 2 cover a larger kinematic range with smaller experimental uncertainties than in the past. Both measurements from p–Pb and Pb–Pb collisions, are compared with predictions of available models.