Energy dependence of exclusive mathrm {J}/psi photoproduction off protons in ultra-peripheral p\u2013Pb collisions at sqrt{s_{mathrm {scriptscriptstyle NN}}} = 5.02 TeV

Abstract

The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of mathrm {J}/psi vector mesons off proton targets in ultra–peripheral p–Pb collisions at a centre-of-mass energy per nucleon pair sqrt{s_mathrm{NN}} = 5.02 TeV. The e^+e^- and mu ^+mu ^- decay channels are used to measure the cross section as a function of the rapidity of the mathrm {J}/psi in the range -2.5< y < 2.7, corresponding to an energy in the gamma p centre-of-mass in the interval 40< W_{gamma mathrm {p}}<550 GeV. The measurements, which are consistent with a power law dependence of the exclusive mathrm {J}/psi 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.