Photoproduction of low-pT J/ψ from peripheral to central Pb-Pb collisions at 5.02 TeV

An excess of J/psi yield at very low transverse momentum (p(T) < 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 root s(NN) = 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 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 root s(NN) = 2.76 TeV, confirming the clear excess over hadronic production in the range GeV/c and the centrality range 70-90%, and establishing an excess with a significance greater than 5s also in the 50-70% and 30-50% centrality ranges. The results are compared with earlier measurements at root s(NN) = 2.76 TeV and with different theoretical predictions aiming at describing how coherent photoproduction occurs in hadronic interactions with nuclear overlap. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3.)