Photoproduction of low-$p_{\mathrm{T}}$ J/$\psi$ from peripheral to central Pb$-$Pb collisions at 5.02 TeV

Abstract

An excess of J/$\psi$ yield at very low transverse momentum ($p_{\mathrm{T}}<0.3$ 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 $\sqrt{s_{\mathrm{NN}}}=5.02$ 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 $p_{\mathrm{T}}$ 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 $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV, confirming the clear excess over hadronic production in the $p_{\mathrm{T}}$ range 0$-$0.3 GeV/$c$ and the centrality range 70$-$90%, and establishing an excess with a significance greater than 5$\sigma$ also in the 50$-$70% and 30$-$50% centrality ranges. The results are compared with earlier measurements at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV and with different theoretical predictions aiming at describing how coherent photoproduction occurs in hadronic interactions with nuclear overlap.

22 pages, 4 captioned figures, 3 tables, authors from page 17, published version, figures at http://alice-publications.web.cern.ch/node/7890

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Cited by in corpus (4)

• The ALICE experiment: a journey through QCD
• Properties of the QCD Matter: A Review of Selected Results from the ALICE Experiment
• Measurements of inclusive J/$\psi$ production at midrapidity and forward rapidity in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• $\psi (2S)$ suppression in Pb-Pb collisions at the LHC