Are the $J/\psi$ and $\chi_c A$ Dependencies the Same?

Abstract

It has been empirically observed that the dependence of $J/\psi$ and $\psi'$ production on nuclear mass number $A$ is very similar. This has been postulated to be due to the predominance of color octet pre-resonant states in charmonium production and absorption. Two new experiments, NA60 at CERN and HERA-B at DESY, will measure the $\chi_c$ $A$ dependence for the first time. These measurements should shed new light on the charmonium production and absorption mechanisms.