(Upper panel) ALICE data (red symbols) on exclusive photoproduction of \jpsi off protons as a function of the centre-of-mass energy of the photon--proton system \Wgp, obtained in collisions of protons and lead nuclei at $\snn=5.02$ TeV, including results from~, compared to a power-law fit, to data from HERA, to the solutions from LHCb\ and to theoretical models (see text). The uncertainties are the quadratic sum of the statistical and systematic uncertainties. (Lower panel) Ratio of the models shown in the upper panel\ to the power law fit through the ALICE data points. The Bjorken x value corresponding to \Wgp is also displayed on the top of the Figure, see text for details. | |