Heavy meson photoproduction in peripheral AA collisions

Abstract

The exclusive photoproduction of the heavy vector mesons ψ and Y is investigated in peripheral Pb-Pb collisions for the energies available at the LHC, ffiffiffi sp ¼ 2.76 TeV and ffiffiffi ps ¼ 5.02 TeV. To evaluate the robustness of the light-cone color dipole formalism, previously tested in the ultraperipheral regime, the rapidity distribution and the nuclear modification factor (RAA) are calculated for the three centrality classes: 30%–50%, 50%–70%, and 70%–90%. The ultraperipheral to peripheral regime transition was carried out by sophisticating the photon flux description and the photonuclear cross section, taking into account the effective interaction area. In our calculations, three scenarios were considered: (scenario 1) the direct application of the usual photon flux and of the photonuclear cross section with no relevant change in relation to the ultraperipheral collision (UPCs), (scenario 2) the application of an effective photon flux keeping the photonuclear cross section unchanged, and (scenario 3) also considering an effective photonuclear cross section. The results obtained with the three different scenarios were compared with the ALICE measurements, showing a better agreement with the data (only J=ψ at the moment) in the more complete approach (scenario 3), mainly in the more central regions (30%–50% and 50%–70%) where the uncertainty is smaller.