Charmonium production and nuclear absorption in p-A interactions at 450 GeV

Abstract.

The production of ${\rm J}/\psi$ and $\psi^\prime$ charmonium states in proton-nucleus interactions has been investigated by the NA50 experiment, at the CERN SPS. High statistics data sets were collected with collisions induced by 450 GeV protons incident on Be, Al, Cu, Ag and W targets. The ${\rm J}/\psi$ and $\psi^\prime$ production cross-sections have been determined for each p-A system and their dependences on the nucleus size have been studied, leading to the so-called normal nuclear absorption. Comparing the two patterns we see that the nuclear absorption is stronger for the $\psi^\prime$ than for the ${\rm J}/\psi$. Given the high statistics of the data samples, the $x_{\rm F}$ (or rapidity) differential cross-sections of the ${\rm J}/\psi$ and $\psi^\prime$ states have also been studied, for each of the target nuclei.