Charmonium dynamics in nucleus-nucleus collisions at SPS and FAIR energies

Charmonium production and suppression in In+In and Pb+Pb reactions at SPS energies is investigated with the HSD transport approach within the 'hadronic comover model' as well as the 'QGP threshold scenario'. The results of the transport calculations for J/Psi suppression and the Psi prime to J/Psi ratio are compared with the recent data of the NA50 and NA60 Collaborations. We find that the comover absorption model - with a single parameter |M_0|^2 for the matrix element squared for charmonium-meson dissociation - performs best with respect to all data sets. The 'threshold scenario' - within different assumptions for the melting energy densities - yields a reasonable suppression for J/Psi but fails in reproducing the Psi prime to J/Psi ratio for Pb+Pb at 158 A GeV. Predictions for Au+Au reactions are presented for a bombarding energy of 25 A GeV in the different scenarios which will allow for a clear distinction between the models from the experimental side at the future FAIR facility.