Charmonia Production at the CERN/SPS

TL;DR

This paper reports on the final results of charmonia production in lead-lead collisions at CERN/SPS, showing increased suppression with centrality and highlighting differences in suppression patterns between J/psi and psi-prime resonances.

Contribution

It provides new measurements of charmonia suppression in Pb-Pb interactions and compares them with p-A data to identify anomalous suppression phenomena.

Findings

J/psi suppression begins at mid-centralities

Psi-prime suppression is stronger and increases in Pb-Pb collisions

Results suggest anomalous suppression beyond normal nuclear absorption

Abstract

We present the final results of experiment NA50 on charmonia production in Pb-Pb interactions at 158 A GeV. A strong increasing suppression is observed with increasing centrality, for both the jpsi and psiprime resonances. We also present new developments regarding the jpsi and psiprime normal nuclear absorption determinations deduced from proton-nucleus data only. Their comparison with Pb-Pb results allows us to conclude that the jpsi anomalous suppression sets in at mid-centralities while the S-U results show a reasonable agreement with the p-A behavior. The psiprime suffers a significantly stronger suppression already in S-U interactions, which continuously increases in the Pb-Pb system, and is completely incompatible with the expected behavior deduced from p-A collisions.