Charmonium production in PbPb interactions at 158 GeV/c per nucleon

Ramello, Luciano; Abreu, M. C.; Alessandro, B.; Alexa, C.; Arnaldi, R.; Astruc, J.; Atavan, M.; Baglin, C.; Baldit, A.; Bedjidian, M.; Bellaiche, F.; Beolè, S.; Boldea, V.; Bordalo, P.; Bussière, A.; Capony, V.; Casagrande, L.; Castor, J.; Chambon, T.; Chaurand, B.; Chevrot, I.; Cheynis, B.; Chiavassa, Emilio Luciano; Cicalò, C.; Comets, M. P.; Constantinescu, S.; Cruz, J.; De Falco, A.; De Marco, N.; Dellacasa, G.; Devaux, A.; Dita, S.; Drapier, O.; Espagnon, B.; Fargeix, J.; Filippov, S. N.; Fleuret, F.; Force, P.; Gallio, Mauro; Gavrilov, Y. K.; Gerschel, C.; Giubellino, P.; Golubeva, M. B.; Gonin, M.; Grigorian, A. A.; Grossiord, J. Y.; Guber, F. F.; Guichard, A.; Gulkanyan, H.; Hakobyan, R.; Haroutunian, R.; Idzik, M.; Jouan, D.; Karavitcheva, T. L.; Kluberg, L.; Kurepin, A. B.; Le Bornec, Y.; Lourenço, C.; Mac Cormick, M.; Macciotta, P.; Marzari Chiesa, A.; Masera, Massimo; Masoni, A.; Mehrabyan, S.; Mourgues, S.; Musso, A.; Ohlsson Malek, F.; Petiau, P.; Piccotti, A.; Pizzi, J. R.; Prado da Silva, W. L.; Puddu, G.; Quintans, C.; Racca, C.; Ramello, L.; Ramos, S.; Rato Mendes, P.; Riccati, L.; Romana, A.; Sartori, S.; Saturnini, P.; Scomparin, E.; Serci, S.; Shahoyan, R.; Silva, S.; Soave, C.; Sonderegger, P.; Tarrago, X.; Temnikov, P.; Topilskaya, N. S.; Usai, G. L.; Vale, C.; Vercellin, Ermanno; Willis, N.

doi:10.1016/S0375-9474(98)00360-1

The NA50 collaboration has measured J/ψ, ψ′ and Drell Yan pair production in Pbsingle bondPb interactions at 158 GeV/c per nucleon at the CERN SPS. Final results from the 1995 run and preliminary ones from the higher statistics 1996 run are presented. A anomalous J/ψ suppression (relative to the Drell-Yan process) has been observed with respect to the suppression pattern established in experiments NA38 and NA51 with proton, oxygen and sulfur beams. The 1996 data allow a detailed study of the suppression pattern in the Pbsingle bondPb sample itself, showing a discontinuity around an ET value (the neutral transverse electromagnetic energy) of 50 GeV. The ψ′ is also suppressed relative to Drell-Yan, with a pattern very similar to the one observed in Ssingle bondU collisions. Finally, the pT distributions of dimuons are presented. The average pT2 of the J/ψ in Pbsingle bondPb collisions does not increase any more with ET above 100 GeV.