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/Ψ suppression and the Ψ′ to J/Ψ ratio are compared with the recent data of the NA50 and NA60 Collaborations. We find that the comover absorption model—with a single parameter 2|M0| 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/Ψ but fails in reproducing the Ψ′ to J/Ψ ratio for Pb + Pb at . Predictions for Au + Au reactions are presented for a bombarding energy of in the different scenarios which will allow for a clear distinction between the models from the experimental side at the future FAIR facility.