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

M.C. Abreu , B. Alessandro , C. Alexa , R. Arnaldi , M. Atayan , C. Baglin (1) , A. Baldit (2) , M. Bedjidian (3) , S. Beole , V. Boldea , P. Bordalo , A. Bussiere (1) , Laurent Capelli (3) , L. Casagrande , J. Castor (2) , T. Chambon (2) , B. Chaurand (4) , I. Chevrot (2) , B. Cheynis (3) , E. Chiavassa , C. Cicalo , M.P. Comets (5) , N. Constans (4) , S. Constantinescu , J. Cruz , A. de Falco , G. Dellacasa , N. de Marco , A. Devaux (2) , S. Dita , O. Drapier (3) , L. Ducroux (3) , B. Espagnon (2) , J. Fargeix (2) , P. Force (2) , M. Gallio , Y.K. Gavrilov , C. Gerschel (5) , P. Giubellino , M.B. Golubeva , M. Gonin (4) , A.A. Grigorian , J.-Y. Grossiord (6) , F.F. Guber , A. Guichard (3) , H. Gulkanyan , R. Hakobyan , R. Haroutunian (3) , M. Idzik , D. Jouan (5) , T.L. Karavitcheva , L. Kluberg (4) , A.B. Kurepin , Y. Le Bornec (5) , C. Lourenco , M. Maccormick (5) , P. Macciotta , A. Marzari-Chiesa , M. Masera , A. Masoni , S. Mehrabyan , M. Monteno , S. Mourgues (2) , A. Musso , P. Petiau (4) , A. Piccotti , J.-R. Pizzi (3) , F. Prino , G. Puddu , C. Quintans , L. Ramello , S. Ramos , P. Rato-Mendes , L. Riccati , A. Romana (4) , I. Ropotar , P. Saturnini (2) , E. Scomparin , S. Serci , R. Shahoyan , S. Silva , M. Sitta , C. Soave , P. Sonderegger , X. Tarrago (5) , N.S. Topilskaya , G.L. Usai , E. Vercellin , L. Villatte (5) , N. Willis (5)

1 LAPP - Laboratoire d'Annecy de Physique des Particules
2 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
3 IPNL - Institut de Physique Nucléaire de Lyon
4 LLR - Laboratoire Leprince-Ringuet
5 IPNO - Institut de Physique Nucléaire d'Orsay
6 ALICE

The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of thepreviously observed \jpsi\ anomalous suppression. This newmeasurement, besides providing a deeper understanding of the previousobservations, reveals a steady significative decrease in the \jpsi\ production rate up to the most central Pb-Pb collisions. It clearlyrules out the presently available conventional (hadronic) models of\jpsi\ suppression, which unanimously predict a saturation of the\jpsi\ rate for central Pb-Pb collisions. On the contrary andtogether with the sharp onset of the anomalous suppression previouslyreported, the new observation leads to a global production ratepattern which finds its natural explanation in the framework of theformation of a deconfined state of quarks and gluons.

Domaines: Physique des Hautes Energies - Phénoménologie [hep-ph]

M.C. Abreu, B. Alessandro, C. Alexa, R. Arnaldi, M. Atayan, et al.. Evidence for deconfinement of quarks and gluons from the $J/psi$ suppression pattern measured in Pb-Pb collisions at the CERN-SPS. Physics Letters B, 2000, 477, pp.28-36. ⟨10.1016/S0370-2693(00)00237-9⟩. ⟨in2p3-00007753⟩