Coherent $\mathrm{J}/\psi$ photoproduction in peripheral heavy-ion collisions
Résumé
In 2015, the ALICE Collaboration reported the first measurement of an excess in the yield of $\mathrm{J}/\psi$ at very low transverse momentum ($p_t < 0.3 \mathrm{GeV}/c$) in the forward rapidity region ($2.5 < y< 4$) in peripheral lead-lead (Pb-Pb) collisions at $\sqrt{s_{NN}} = 2.76 \mathrm{TeV}$ at the CERN LHC. The coherent photoproduction was proposed as the potential underlying physics mechanism. This is known to be the main production mechanism for low-$p_T$ $\mathrm{J}/\psi$ production in ultra-peripheral collisions, which are dominated by electromagnetic interactions. However, the observation of a large effect in more central collisions that are dominated by the hadronic interactions was quite surprising. This article represents a proceeding contribution on the preliminary results from PbPb collisions at $\sqrt{s_{NN}} = 5.02 \mathrm{TeV}$ shown in a poster during the National Congress of the French Physical Society in July 2019.