Bochum 2009 – scientific programme

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HK: Fachverband Hadronen und Kerne

HK 33: Heavy Ion Collisions and QCD phases

HK 33.3: Talk

Tuesday, March 17, 2009, 17:30–17:45, H-ZO 10

Decreasing elliptic flow at the CERN Large Hadron Collider: Calculations in a parton recombination approach — •Daniel Krieg and Marcus Bleicher — Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany

We apply the colinear parton recombination approach to study the energy dependence of the mean elliptic flow, v₂ in heavy ion collisions from AGS to LHC energies. The relevant input quantities (T, µ_B, η_T) at the various center of mass energies are obtained from fits to the available data, while η_T is the only relevant quantity for the LHC prediction. The model yields a good description of the integrated v₂ data for charged particles at midrapidity from AGS to RHIC energies. In stark contrast to the current expectations, we observe a decrease of the integrated v₂ values above the highest RHIC energy. Thus, we predict a decrease of v₂ at LHC energies compared to the RHIC results [Phys. Rev. C 78, 054903 (2008)]. This drop is attributed to negative v₂ values for the underlying parton distributions at low to moderate transverse momenta that develops if the transverse flow velocity is high enough. At energies above the LHC regime, the present approach predicts even negative values for the integrated v₂. These negative values seem to be a general feature of the employed blast-wave parameterization for parton distributions and they have also been experimentally observed by the NA49 collaboration. These results are supported by the recent preliminary data on J/ψ elliptic flow from PHENIX and our corresponding calculations [arXiv:0806.0736].