An excess of J/ψ yield at very low transverse momentum (pT < 0.3 GeV/c), originating from coherent
photoproduction, is observed in peripheral and semicentral hadronic Pb–Pb collisions at a center-of-
mass energy per nucleon pair of √sNN = 5.02 TeV. The measurement is performed with the ALICE
detector via the dimuon decay channel at forward rapidity (2.5 < y < 4). The nuclear modification factor
at very low pT and the coherent photoproduction cross section are measured as a function of centrality
down to the 10% most central collisions. These results extend the previous study at √sNN = 2.76 TeV,
confirming the clear excess over hadronic production in the pT range 0 − 0.3 GeV/c and the centrality
range 70–90%, and establishing an excess with a significance greater than 5σ also in the 50–70% and
30–50% centrality ranges. The results are compared with earlier measurements at √sNN = 2.76 TeV
and with different theoretical predictions aiming at describing how coherent photoproduction occurs
in hadronic interactions with nuclear overlap.
