Negative elliptic flow of J/ψ’s: A qualitative signature for charm collectivity at RHIC
Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, 60438, Frankfurt am Main, Germany
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Revised: 9 December 2008
Published online: 22 December 2008
We discuss one of the most prominent features of the very recent preliminary elliptic flow data of J/ψ-mesons from the PHENIX Collaboration (PHENIX Collaboration (C. Silvestre), arXiv:0806.0475 [nucl-ex]). Even within the rather large error bars of the measured data a negative elliptic flow parameter (v2) for J/ψ in the range of p T = 0.5-2.5 GeV/c is visible. We argue that this negative elliptic flow at intermediate pT is a clear and qualitative signature for the collectivity of charm quarks produced in nucleus-nucleus reactions at RHIC. Within a parton recombination approach we show that a negative elliptic flow puts a lower limit on the collective transverse velocity of heavy quarks. The numerical value of the transverse flow velocity for charm quarks that is necessary to reproduce the data is (charm) ∼ 0.55-0.6c and therefore compatible with the flow of light quarks.
PACS: 25.75.Ld Collective flow – / 12.38.Mh Quark-gluon plasma – / 14.20.Lq Charmed baryons –
© SIF, Springer-Verlag Berlin Heidelberg, 2009