Charmonium dissociation in hadronic matter

Production of $J/\psi$ from nucleus-nucleus reactions depends sensitively on the dissociation cross section with light hadrons. Effective Lagrangian methods are used to describe the hadronic degrees of freedom, including strangeness and charm. Cross sections with pions, rho mesons, kaons, and nucleons having magnitudes 4–8 mb are found, and with steep thresholds. This, folded with thermal momentum distributions for the scattering partners, suggests a mean dissociation lifetime $\simeq 20\mathrm{fm}/c.\mathrm{}$ Therefore, the “abnormal” $J/\psi$ suppression seen in recent $\mathrm{Pb}+\mathrm{Pb}$ experiments seems to owe a debt to expected hadron kinetics.