Energy dependence of exclusive J/ψ photoproduction off protons in ultra-peripheral p–Pb collisions at √sNN = 5.02 TeV

The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of J/ vector mesons off proton targets in ultra-peripheral p-Pb collisions at a centre-of-mass energy per nucleon pair s NN = 5.02 TeV. The e + e -and + -decay channels are used to measure the cross section as a function of the rapidity of the J/ in the range -2.5 < y < 2.7, corresponding to an energy in the p centre-of-mass in the interval 40 < W p < 550 GeV. The measurements, which are consistent with a power law dependence of the exclusive J/ photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements.