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

TL;DR

This paper investigates the elliptic flow of various hadrons in 200 GeV Au+Au collisions at RHIC, revealing scaling behaviors and centrality dependence that shed light on the collective dynamics of the quark-gluon plasma.

Contribution

It provides a detailed analysis of the centrality dependence of elliptic flow for different hadrons, including multi-strange particles, using multiple analysis methods and scaling tests.

Findings

Elliptic flow scales with m_T - m at low p_T.

v_2 scales with quark number at intermediate p_T.

Stronger collective flow observed in more central collisions.

Abstract

We present STAR results on the elliptic flow v_2 of charged hadrons, strange and multi-strange particles from sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC. The detailed study of the centrality dependence of v_2 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 v_2 with the Lee-Yang Zero method for K_s^0 and Lambda. In the relatively low p_T region, p_T <= 2 GeV/c, a scaling with m_T - m is observed for identified hadrons in each centrality bin studied. However, we do not observe v_2(p_T) scaled by the participant eccentricity to be independent of centrality. At higher p_T, 2 GeV/c <= p_T <= 6 GeV/c, v_2 scales with quark number for all hadrons studied. For the multi-strange hadron Omega, which does not suffer appreciable hadronic interactions, the values of v_2 are consistent with both m_T -m scaling at low p_T and number-of-quark scaling at intermediate p_T. As a function of collision centrality, an increase of p_T-integrated v_2 scaled by the participant eccentricity has been observed, indicating a stronger collective flow in more central Au+Au collisions.