[en] This paper proposes that the formation of a quark gluon plasma in nucleus-nucleus collisions is signalled by a drop in the cross section for J/ψ production. Here we present the preliminary results of the J/ψ production cross section computed pertubatively, and the nuclear effects introduced through the known EMC-effect on quark distributions. A suppression of upto 40% could then occur. It has been suggested that a suppression of J/ψ formation cross section in relativistic nucleus-nucleus (AA) collisions signals the production of a quark gluon plasma (QCP). Since a reliable estimate of rates depends on the values of many presently unknown characteristics of the plasma, it is of interest to compute this cross section assuming no plasma forms. The models on which these predictions are based must then be thoroughly tested in other domains. Once proved, any deviations can be taken to signal the occurrence of new physics