Thermal Production of Charmonia at the LHC Energies.
This work studies the thermal production of $J/\psi$ and $\psi(2S)$ with Boltzmann transport model in the Quark Gluon Plasma (QGP) produced in $\sqrt{s_{NN}}=5.02$ TeV Pb-Pb collisions. $J/\psi$ nuclear modification factors are studied in details with the mechanisms of primordial production and the recombination of charm and anti-charm quarks in the thermal medium. $\psi(2S)$ binding energy is much smaller in the hot medium compared with the ground state, so $\psi(2S)$ with middle and low $p_T$ can be mainly thermally regenerated in the later stage of QGP expansions which enables $\psi(2S)$ inherit larger collective flows from the bulk medium. We quantitatively study both nuclear modification factors of $J/\psi$ and $\psi(2S)$ in different centralities and transverse momentum bins in $\sqrt{s_{NN}}=5.02$ TeV Pb-Pb collisions.