On the Possibility of Thermalization of Heavy Mesons in Ultrarelativistic Nuclear Collisions

The phenomenological analysis and interpretation of experimental data from RHIC and LHC on the production of J/Psi and D mesons in heavy-ion collisions are performed within the two-component HYDJET++ model including the thermal and hard mechanisms of hadron production. It is shown that the thermal freeze-out of charmed mesons at RHIC energies occurs earlier than the thermal freeze-out of light hadrons (assumingly, simultaneously with chemical freeze-out), which indicates that J/Psi and D mesons are not in kinetic equilibrium with the formed hadronic matter. At the same time, a significant part of D mesons at LHC energies are in kinetic equilibrium with the formed thermalized matter, but J/Psi mesons are still characterized by early freeze-out.