298 articles – 2313 Notices  [english version]
 HAL : in2p3-00382161, version 1
 3rd International Conference On Hard And Electromagnetic Probes Of High-Energy Nuclear Collisions (HP2008), Illa da Toxa : Espagne (2008)
 J / ψ azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon
 NA50 Collaboration(s)
 (2009)
 The J/ψ azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/ψ mesons at SPS energies. Hence, the measurement of J/ψ elliptic anisotropy, quantified by the Fourier coefficient v 2 of the J/ψ azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/ψ suppression observed in Pb-Pb collisions. We present the measured J/ψ yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v _{2} as a function of the collision centrality and of the J/ψ transverse momentum. The reaction plane has been estimated from the azimuthal distribution of the neutral transverse energy detected in an electromagnetic calorimeter. The analysis has been performed on a data sample of about 100 000 events, distributed in five centrality or p_{T} sub-samples. The extracted v_{ 2} values are significantly larger than zero for non-central collisions and are seen to increase with p_{T}
 Thème(s) : Physique/Physique Nucléaire Expérimentale
 in2p3-00382161, version 1 http://hal.in2p3.fr/in2p3-00382161 oai:hal.in2p3.fr:in2p3-00382161 Contributeur : Jeanine Pellet <> Soumis le : Jeudi 7 Mai 2009, 14:35:36 Dernière modification le : Jeudi 6 Août 2009, 10:02:10