Coherent photoproduction of ρ 0 vector mesons in ultra-peripheral Pb-Pb collisions at √sNN = 5.02 TeV

Abstract

Cross sections for the coherent photoproduction of ρ 0 vector mesons in ultraperipheral Pb-Pb collisions at √ sNN = 5.02 TeV are reported. The measurements, which rely on the π +π − decay channel, are presented in three regions of rapidity covering the range |y| < 0.8. For each rapidity interval, cross sections are shown for different nuclearbreakup classes defined according to the presence of neutrons measured in the zero-degree calorimeters. The results are compared with predictions based on different models of nuclear shadowing. Finally, the observation of a coherently produced resonance-like structure with a mass around 1.7 GeV/c 2 and a width of about 140 MeV/c 2 is reported and compared with similar observations from other experiments