Quark exchange model for charmonium dissociation in hot hadronic matter.

A diagrammatic approach to quark exchange processes in meson-meson scattering is applied to the case of inelastic reactions of the type (Q ¯ Q) + (q¯ q) → (Q¯ q)+(q ¯ Q), where Q and q refer to heavy and light quarks, respectively. This string-flip process is discussed as a microscopic mechanism for charmonium dissociation (absorption) in hadronic matter. The cross section for the reaction J/ψ + π → D + ¯ D is calculated using a potential model, which is fitted to the meson mass spectrum. The temperature dependence of the relaxation time for the J/ψ distribution in a homogeneous thermal pion gas is obtained. The use of charmonium for the diagnostics of the state of hot hadronic matter produced in ultrarelativistic nucleus-nucleus collisions is discussed.