J/psi production in p-A and A-A collisions at fixed target experiments

TL;DR

This paper reviews J/psi production in p-A and A-A fixed target experiments, emphasizing nuclear effects, new experimental results, and polarization measurements to distinguish hot medium effects from cold nuclear matter influences.

Contribution

It provides new NA60 results at 158 GeV, compares them with other experiments, and discusses the impact of cold nuclear matter on J/psi suppression and polarization.

Findings

NA60 results at 158 GeV are consistent with previous p-A data.

Cold nuclear matter effects significantly influence J/psi yields.

J/psi polarization measurements offer additional insights into production mechanisms.

Abstract

Charmonia suppression is one of the main signatures for the formation of a deconfined medium. However, also nuclear effects, not related to the production of a hot medium, can affect the J/psi yield. The determination, from the study of p-A collisions, of the J/psi behaviour in nuclear matter is, therefore, extremely important to correctly quantify the amount of charmonia suppression induced by the deconfined medium. In this paper the new NA60 results collected at 158 GeV incident energy, i.e. under the same kinematical conditions as the In-In (NA60) and Pb-Pb (NA50) data, are presented and compared with p-A measurements from other fixed target experiments. Results on A-A collisions are also reviewed taking into account the new available information on the influence of cold nuclear matter on the J/psi production yield. Finally, results on the J/psi polarization are shown for p-A and A-A collisions.