Evidence for deconfinement of quarks and gluons from the J/psi suppressionpattern measured in Pb-Pb collisions at the CERN-SPS

The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of the previously observe d J/psi, anomalous suppression. This new measurement, besides providing a d eeper understanding of the previous observations, reveals a steady signific ative decrease in the J/psi production rate up to the most central Pb-Pb co llisions. It clearly rules out the presently available conventional (hadron ic) models of J/psi suppression, which unanimously predict a saturation of the J/psi rate for central Pb-Pb collisions. On the contrary and together w ith the sharp onset of the anomalous suppression previously reported, the n ew observation leads to a global production rate pattern which finds its na tural explanation in the framework of the formation of a deconfined state o f quarks and gluons. (C) 2000 Elsevier Science B.V. All rights reserved.