Contribution of pre-equilibrium gluons to J/Ψ suppression in Lead-Lead collisions at 158AGeV

We point out that dissociation of J/Ψ by partons (mostly gluons) produced in semi-hard nucleon-nucleon sub-collisions may explain at least a part of the spectacular J/Ψ suppression observed recently by the NA-50 Collaboration in Pb-Pb interactions at the CERN-SPS.Our arguments are based on a model in which individual nucleon-nucleon interactions in heavy ion collisions are harder than interactions between free nucleons due to the Landau-Pomeranchuk effect. Suppression by semi-hard partons represents an additional factor to the Gerschel-Hüfner mechanism of J/Ψ suppression by nucleons. Conclusions we are able to make are to be considered as rather qualitative since accurate estimates of various parameters used are not available.We make a conjecture that the new phenomenon observed by the NA-50 Collaboration is connected with a large density of gluons produced in semi-hard nucleonnucleon collisions.The density approaches or slightly exceedes in a small volume and for a short time the critical density required for the phase transition to QuarkGluon Plasma.