Dissociation kinetics and momentum-dependentJψsuppression in a quark-gluon plasma

A quantum-statistical approach to two-particle states in a surrounding plasma is applied to heavy quarkonia. Thermal activation and dissociation of charmonium and bottomonium bound states is described by chemical reaction kinetics. The momentum dependence of the $\frac{J}{\psi }$ suppression ratio is related to the temperature and the lifetime of the plasma phase. From recently observed data for high-energy nucleus-nucleus collisions, a plasma lifetime of the order of 20 fm/c is estimated.