CERN Accelerating science

The J$/\psi$ mesons is a bound state of a charm quark and its anti-quark. The production of J$/\psi$ mesons serves as an important probe of the quark-gluon plasma (QGP) formed in heavy-ion collisions. The presence of the deconfined strongly interacting medium results in the color screening of the potential between charm quarks and anti-quarks created during hard scattering processes. At sufficiently high collision energies such as the LHC energy, the large abundance of produced charm quarks leads to the (re)generation of J$/\psi$ mesons during the QGP evolution and/or at the phase boundary. In this work, the J$/\psi$ production yield in Pb-Pb collisions at $\sqrt{s_\textrm{NN}}=5.02$ TeV recorded by ALICE is measured at midrapidity via the dielectron decay channel J$/\psi \rightarrow \textrm{e}^+\textrm{e}^-$ as a function of centrality and as a function of transverse momentum down to $p_\textrm{T}=0.15$ GeV/$c$ in the most central and semi-central collisions. The J$/\psi$ nuclear modification factor $R_\textrm{AA}$ increases slightly from semi-central to the most central collisions. The $p_\textrm{T}$-differential J$/\psi$ $R_\textrm{AA}$ shows a large suppression of the J$/\psi$ yield at high $p_\textrm{T}$ and the J$/\psi$ $R_\textrm{AA}$ increases with decreasing $p_\textrm{T}$. The measurement is compared to other experimental results and to model calculations. The presented results strongly support picture of (re)generation as an important J$/\psi$ production mechanism at the LHC especially significant at low $p_\textrm{T}$ and at midrapidity.