J/ψSuppression in Pb+Pb Collisions: A New Look at Hadrons vs. Plasma

A reexamination of hadronic comover scattering indicates that this mechanism cannot explain the observed $J/\psi$ suppression in Pb+Pb interactions. The possibility of quark-gluon plasma formation is then plausible. We present calculations in which the $\chi_c$ and $\psi'$ are suppressed by the plasma while the $J/\psi$ itself is not.