Dissociation of heavy quarkonia in the quark$ndash$gluon plasma

Using a temperature-dependent potential obtained from lattice gauge calculations of Karsch et al , we study the stability of heavy quarkonia in the quark–gluon plasma. We find that only the Υ(1 S ) and η b (1 S ) are bound in the quark–gluon plasma, and have a small binding energy. The quark–gluon plasma may be revealed by an Υ(1 S ) dilepton peak with an invariant mass close to twice the current b quark mass, which is lower than the Υ(1 S ) mass in free space. The quarkonia Υ(1 S ) and η b (1 S ) can dissociate by collision with quarks and gluons in the quark–gluon plasma. The Υ(1 S ) and the η b (1 S ) can also dissociate spontaneously at temperatures above the dissociation temperature 1.11 T c , where T c is the quark–gluon plasma phase transition temperature. At temperatures slightly above the dissociation temperature these states appear as resonances, which provides another signature for the quark–gluon plasma.