Centrality dependence of charged hadron and strange hadron elliptic flow from sqrt(sNN) = 200 GeV Au+Au collisions

Abstract

We present STAR results on the elliptic flow v2 of charged hadrons, strange and multi-strange particles from sqrt(sNN) = 200 GeV Au+Au collisions at RHIC. The detailed study of the centrality dependence of v2 over a broad transverse momentum range is presented. Comparison of different analysis methods are made in order to estimate systematic uncertainties. In order to discuss the non-flow effect, we have performed the first analysis of v2 with the Lee-Yang Zero method for Ks0 and Lambda. In the relatively low pT region, pT <= 2 GeV/c, a scaling with mT - m is observed for identified hadrons in each centrality bin studied. However, we do not observe v2(pT) scaled by the participant eccentricity to be independent of centrality. At higher pT, 2 GeV/c <= pT <= 6 GeV/c, v2 scales with quark number for all hadrons studied. For the multi-strange hadron Omega, which does not suffer appreciable hadronic interactions, the values of v2 are consistent with both mT -m scaling at low pT and number-of-quark scaling at intermediate pT. As a function of collision centrality, an increase of pT-integrated v2 scaled by the participant eccentricity has been observed, indicating a stronger collective flow in more central Au+Au collisions.