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

Authors：Acharya, S.; Adamova, D.; Adler, A.; Rinella, G. Aglieri; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Ahuja, I.; Akindinov, A.; Al-Turany, M.; Aleksandrov, D.; Alessandro, B.; Alfanda, H. M.; Molina, R. Alfaro; Ali, B.; Ali, Y.; Alici, A.; Alizadehvandchali, N.; Alkin, A.; Alme, J.; Alocco, G.; Alt, T.; Altsybeev, I.; Anaam, M. N.; Andrei, C.; Andronic, A.; Anguelov, V.; Antinori, F.; Antonioli, P.; Anuj, C.; Apadula, N.; Aphecetche, L.; Appelshauser, H.; Arcelli, S.

Source：Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics , 2023, 846: 137467.

DOI：10.1016/j.physletb.2022.137467

• NUCLEAR MODIFICATION
• COHERENT J/PSI
• PPB COLLISIONS
• MID-RAPIDITY
• CHARMONIUM
• SUPPRESSION
• PROMPT
• DEPENDENCE

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.