Charmonium Production in gamma-A, p-A and A-A

Abstract

The data for the production of the ${\psi }^{\prime }$ meson in pA collisions at 450 GeV at CERN-SPS (of the NA50-collaboration) yields $\sigma ({\psi }^{\prime }N)\approx 8$ mb under the assumption that the ${\psi }^{\prime }$ is produced as a result of the space-time evolution of a point-like $c\bar{c}$ pair which expands with time to the full size of the charmonium state. However, much higher values of $\sigma ({\psi }^{\prime }N)$ are not ruled out by the data. We show that recent CERN data confirm the suggestion that color fluctuations are the major source of suppression of the $J/\psi$ yield as observed at CERN in both pA and AA collisions.

Comments: 7 pages, 3 figures, talk given at the Strange Quark Matter Conference, Atlantic Beach, North Carolina, March 12-17, 2003