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The European Physical Journal C

, Volume 61, Issue 4, pp 853–858 | Cite as

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

  • F. PrinoEmail author
  • B. Alessandro
  • C. Alexa
  • R. Arnaldi
  • M. Atayan
  • S. Beolè
  • V. Boldea
  • P. Bordalo
  • G. Borges
  • C. Castanier
  • J. Castor
  • B. Chaurand
  • B. Cheynis
  • E. Chiavassa
  • C. Cicalò
  • M. P. Comets
  • S. Constantinescu
  • P. Cortese
  • A. De Falco
  • N. De Marco
  • G. Dellacasa
  • A. Devaux
  • S. Dita
  • J. Fargeix
  • P. Force
  • M. Gallio
  • C. Gerschel
  • P. Giubellino
  • M. B. Golubeva
  • A. A. Grigoryan
  • S. Grigoryan
  • F. F. Guber
  • A. Guichard
  • H. Gulkanyan
  • M. Idzik
  • D. Jouan
  • T. L. Karavicheva
  • L. Kluberg
  • A. B. Kurepin
  • Y. Le Bornec
  • C. Lourenço
  • M. Mac Cormick
  • A. Marzari-Chiesa
  • M. Masera
  • A. Masoni
  • M. Monteno
  • A. Musso
  • P. Petiau
  • A. Piccotti
  • J. R. Pizzi
  • G. Puddu
  • C. Quintans
  • L. Ramello
  • S. Ramos
  • L. Riccati
  • H. Santos
  • P. Saturnini
  • E. Scomparin
  • S. Serci
  • R. Shahoyan
  • F. Sigaudo
  • M. Sitta
  • P. Sonderegger
  • X. Tarrago
  • N. S. Topilskaya
  • G. L. Usai
  • E. Vercellin
  • L. Villatte
  • N. Willis
  • T. Wu
Open Access
Regular Article - Experimental Physics

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.

Keywords

Reaction Plane Electromagnetic Calorimeter Event Plane Combinatorial Background Azimuthal Distribution 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag / Società Italiana di Fisica 2009

Authors and Affiliations

  • F. Prino
    • 10
    Email author
  • B. Alessandro
    • 10
  • C. Alexa
    • 3
  • R. Arnaldi
    • 10
  • M. Atayan
    • 12
  • S. Beolè
    • 10
  • V. Boldea
    • 3
  • P. Bordalo
    • 6
  • G. Borges
    • 6
  • C. Castanier
    • 2
  • J. Castor
    • 2
  • B. Chaurand
    • 9
  • B. Cheynis
    • 11
  • E. Chiavassa
    • 10
  • C. Cicalò
    • 4
  • M. P. Comets
    • 8
  • S. Constantinescu
    • 3
  • P. Cortese
    • 1
  • A. De Falco
    • 4
  • N. De Marco
    • 10
  • G. Dellacasa
    • 1
  • A. Devaux
    • 2
  • S. Dita
    • 3
  • J. Fargeix
    • 2
  • P. Force
    • 2
  • M. Gallio
    • 10
  • C. Gerschel
    • 8
  • P. Giubellino
    • 10
  • M. B. Golubeva
    • 7
  • A. A. Grigoryan
    • 12
  • S. Grigoryan
    • 12
  • F. F. Guber
    • 7
  • A. Guichard
    • 11
  • H. Gulkanyan
    • 12
  • M. Idzik
    • 13
  • D. Jouan
    • 8
  • T. L. Karavicheva
    • 7
  • L. Kluberg
    • 5
    • 9
  • A. B. Kurepin
    • 7
  • Y. Le Bornec
    • 8
  • C. Lourenço
    • 5
  • M. Mac Cormick
    • 8
  • A. Marzari-Chiesa
    • 10
  • M. Masera
    • 10
  • A. Masoni
    • 4
  • M. Monteno
    • 10
  • A. Musso
    • 10
  • P. Petiau
    • 9
  • A. Piccotti
    • 10
  • J. R. Pizzi
    • 11
  • G. Puddu
    • 4
  • C. Quintans
    • 6
  • L. Ramello
    • 1
  • S. Ramos
    • 6
  • L. Riccati
    • 10
  • H. Santos
    • 6
  • P. Saturnini
    • 2
  • E. Scomparin
    • 10
  • S. Serci
    • 4
  • R. Shahoyan
    • 6
  • F. Sigaudo
    • 10
  • M. Sitta
    • 1
  • P. Sonderegger
    • 5
  • X. Tarrago
    • 8
  • N. S. Topilskaya
    • 7
  • G. L. Usai
    • 4
  • E. Vercellin
    • 10
  • L. Villatte
    • 8
  • N. Willis
    • 8
  • T. Wu
    • 8
  1. 1.Univ. del Piemonte OrientaleAlessandria and INFN-TorinoItaly
  2. 2.LPCUniv. Blaise Pascal and CNRS-IN2P3AubièreFrance
  3. 3.IFABucharestRomania
  4. 4.Univ. di Cagliari/INFNCagliariItaly
  5. 5.CERNGenevaSwitzerland
  6. 6.LIPLisbonPortugal
  7. 7.INRMoscowRussia
  8. 8.IPNUniv. de Paris-Sud and CNRS-IN2P3OrsayFrance
  9. 9.Laboratoire Leprince-RinguetEcole Polytechnique and CNRS-IN2P3PalaiseauFrance
  10. 10.Univ. di Torino/INFNTorinoItaly
  11. 11.IPNUniv. Claude Bernard Lyon-I and CNRS-IN2P3VilleurbanneFrance
  12. 12.YerPhIYerevanArmenia
  13. 13.Faculty of Physics and Applied Computer ScienceAGH Univ.CracowPoland

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