On J/psi Production in Nuclear Collisions
  Data on J/psi production in inelastic proton-proton, proton-nucleus and nucleus-nucleus interactions at 158 A GeV are analyzed and it is shown that the ratio of mean multiplicities of J/psi mesons and pions is the same for all these collisions. This observation is difficult to understand within current models of J/psi production in nuclear collisions based on the assumption of hard QCD creation of charm quarks. 
Marek Gazdzicki