(Non)thermal aspects of charmonium production and a new look at J/ ψ suppression

Abstract

To investigate a recent proposal that J/ ψ production in ultra-relativistic nuclear collisions is of thermal origin we have reanalyzed the data from the NA38/50 Collaboration within a thermal model including charm. Comparison of the calculated with measured yields demonstrates the non-thermal origin of hidden charm production at SPS energy. However, the ratio ψ′/(J/ ψ) exhibits, in central nucleus-nucleus collisions, thermal features which lead us to a new interpretation of open charm and charmonium production at SPS energy. Implications for RHIC and LHC energy measurements will be discussed.