Tübingen 2003 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 47: Physik mit schweren Ionen V

HK 47.1: Gruppenbericht

Donnerstag, 20. März 2003, 16:30–17:00, E

Flow and Semihard Azimuthal Correlations of High-p_T Pions in 158 AGeV/c Pb+Au Collisions — •Jana Slivova — Physikalisches Institut der Universität Heidelberg

Systematic investigation of azimuthal anisotropies can shed light on our knowledge of the equation of state and properties of nuclear matter under extreme conditions achieved in ultra-relativistic heavy-ion collisions.

Using a large data set of 158 AGeV/c Pb+Au collisions measured by the CERES/NA45 experiment we have extracted elliptic event anisotropies (v₂) of charged particles (p_T>0.2 GeV/c) and high-p_T pions (p_T>1.0 GeV/c) employing the standard flow analysis with respect to the event plane and the two-particle azimuthal correlation method. Hydrodynamical calculations are consistent with the observed decrease of the elliptic anisotropy with centrality, but overestimate the magnitude. The coefficient v₂ rises linearly with p_T and shows an onset of saturation around 1.5 GeV/c (v₂≈ 12% at σ/σ_geo=(23-30)%). The two-particle azimuthal correlations of high-p_T pions show systematically higher v₂ values than those obtained from the event plane method. The strength of the non-flow component grows with p_T and is significantly larger than the estimated contribution from HBT correlations. The data suggest an explanation based on semihard processes.