Suppression of Psi' and J/Psi in High-Energy Heavy-Ion Collisions

The experimental ratio of $\psi'$ to $J/\psi$ is approximately a constant in $pA$ collisions, but decreases as the transverse energy increases in nucleus-nucleus collisions. These peculiar features can be explained as arising from approximately the same $c \bar c$-baryon absorption cross section for $\psi'$ and $J/\psi$ but greater disruption probabilities for $\psi'$ than for $J/\psi$ due to the interaction of the $c\bar c$ system with soft particles produced in baryon-baryon collisions.