$J/Psi$ suppression at SPS, RHIC and LHC energies and the percolation of strings

We study the enhancement of $c bar c$ pair production that takes place in central heavy ion collisions due to the formation of clusters of strings. These clusters produce heavy flavors more efficiently due to their higher color. We discuss the competition between this mechanism and the well-known screening of color charge, which, above a critical string density, reduces strongly the probability of binding these $c bar c$ pairs to form $J/Psi$ particles. The dependence of $J/Psi$ suppression on the centrality shows a peak at both RHIC and LHC energies corresponding to the percolation critical density.