Hadroproduction of J/ψ at large p_T and its relevance to a signal of quark gluon plasma

Abstract

Using the parton fusion model of perturbative QCD, we compute the production cross sections of J/ψ at large p_T in pp, h(=π, p)A and AA collisions. The quark structure functions which we use are parametrised in a model-dependent manner to incorporate the well-known EMC-effect, whereas our nuclear gluon densities are as yet untested predictions of the model. Comparison of our computations withpp data and πA data suggests that in the respective kinematic ranges the perturbative QCD model works reasonably well and the predicted nuclear gluon density is a good description of the data. Having thus tested the ingredients of our computations, we compute the ratios of J/ψ production in the central regions of AA, pA and pp as a function of the p_T of the J/ψ. Our results show a remarkable qualitative similarity to the proposed signature of the quark-gluon plasma, making its identification by this signature a fully quantitative task.