# J / ψ azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon

Abstract : 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}
Document type :
Conference papers

http://hal.in2p3.fr/in2p3-00382161
Contributor : Jeanine Pellet <>
Submitted on : Thursday, May 7, 2009 - 2:35:36 PM
Last modification on : Wednesday, October 14, 2020 - 3:42:32 AM

### Citation

F. Prino, B. Alessandro, C. Alexa, R. Arnaldi, M. Atayan, et al.. J / ψ azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon. 3rd International Conference On Hard And Electromagnetic Probes Of High-Energy Nuclear Collisions (HP2008), Jun 2008, Illa da Toxa, Spain. pp.853-858, ⟨10.1140/epjc/s10052-009-0907-4⟩. ⟨in2p3-00382161⟩

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