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

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