Breakdown of [formula omitted]-factorization and [formula omitted] production in dA collisions

Abstract

In spite of the sweeping coherence effects in high energy hadron and nuclei collisions, k T -factorization can be recovered for the inclusive gluon production in pA collisions at the leading logarithmic order. In open charm production at RHIC k T -factorization holds numerically with about 10–20% accuracy. This allows to extrapolate the cold nuclear matter effect observed in light and charm meson production in dA collisions to that in AA ones. Unlike the open charm, the breakdown of factorization in J / ψ production is severe. Indeed, already at the lowest order in gluon density the main contribution to the inclusive cross section is proportional to the square of gluon density in the nucleus. As a consequence, one cannot infer the cold nuclear matter effect on J / ψ production in AA collisions from that in dA. We present the calculation of J / ψ multiplicity in the framework of the CGC (color glass condensate)/saturation and show that it agrees with the experimental data.