$J/\psi$ production in Au+Au/Cu+Cu collisions at $\sqrt{s}_{NN}$=200 GeV   and the threshold model
  Using the QGP motivated threshold model, where all the $J/\psi$'s are suppressed above a threshold density, we have analyzed the preliminary PHENIX data on the centrality dependence of nuclear modification factor for $J/\psi$'s in Cu+Cu and in Au+Au collisions, at RHIC energy, $\sqrt{s}_{NN}$=200 GeV. Centrality dependence of $J/\psi$ suppression in Au+Au collisions are well explained in the model for threshold densities in ranges of 3.6-3.7 $fm^{-2}$. $J/\psi$ suppression in Cu+Cu collisions on the other hand are not explained in the model. 
A. K. Chaudhuri