Observation of a threshold effect in the anomalous J/psi suppression

Citation
Mc. Abreu et al., Observation of a threshold effect in the anomalous J/psi suppression, PHYS LETT B, 450(4), 1999, pp. 456-466
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICS LETTERS B
ISSN journal
0370-2693 → ACNP
Volume
450
Issue
4
Year of publication
1999
Pages
456 - 466
Database
ISI
SICI code
0370-2693(19990325)450:4<456:OOATEI>2.0.ZU;2-4
Abstract
We report on a search for a phase transition from ordinary nuclear matter t o a state of deconfined quarks and gluons as predicted by lattice QCD calcu lations. A new measurement of charmonium production in Pb-Pb interactions a t 158 GeV/c per nucleon agrees with our previous results and confirms the a nomalous J/psi suppression we had already observed on a significantly small er data sample. New event selection and analysis techniques show that, for peripheral collisions, the J/psi cross-section per nucleon-nucleon collisio n agrees with the precise suppression pattern inferred from a wide range of measurements extending from p-p up to S-U collisions. As the collisions be come more central, the Pb-Pb cross-section exhibits a clear departure from this normal behaviour. The onset of the anomalous J/psi suppression reporte d here is the first clear observation of a threshold effect in heavy ion co llisions and can be considered as a strong indication of the production of a deconfined quark-gluon phase in central Pb-Pb collisions. (C) 1999 Elsevi er Science B.V. All rights reserved.