Medium effects on charmonium production at ultrarelativistic energies available at the CERN Large Hadron Collider

We investigate with a transport approach the cold and hot nuclear matter effects on the charmonium transverse momentum distributions in relativistic heavy ion collisions. The newly defined nuclear modification factor rAA=pT²AA/pT²ₚₚ and elliptic flow v₂ for J/ψ are sensitive to the nature of the hot medium and the thermalization of heavy quarks. From Super Proton Synchrotron (SPS) through Relativistic Heavy Ion Collider (RHIC) to Large Hadron Collider (LHC) colliding energies, we observe dramatic changes in the centrality dependence of rAA. We find that, at LHC energy, the finally observed charmonia are dominated by the regeneration from thermalized heavy quarks.