System size, energy and centrality dependence of strange hadron elliptic flow at STAR

TL;DR

This paper investigates how system size, energy, and collision centrality influence the elliptic flow of strange hadrons in heavy ion collisions at RHIC, revealing insights into the early-stage partonic collectivity and collision dynamics.

Contribution

It provides detailed measurements of v2 dependence on centrality, system size, and energy for various strange hadrons, highlighting the limitations of ideal hydrodynamics at RHIC.

Findings

v2 exhibits system size and energy dependence

Number of quark scaling holds across different conditions

Ideal hydrodynamical limit is not fully reached at RHIC

Abstract

The elliptic flow (v2) pattern in terms of hadron mass and transverse momentum pT is qualitatively described for pT < 2 GeV/c by ideal hydrodynamics in Au + Au collisions at RHIC. In addition, for pT = 2 - 6 GeV/c the measured v2 follow a universal scaling by the number of quarks explained by quark coalescence/recombination models. These observations suggest that a partonic collectivity develops in the matter in early stage of heavy ion collisions. Centrality as well as system size and energy dependence of the v2 is important to shed light on the underlying collision dynamics in heavy ion collisions. We present the measurements of centrality dependence of v2 at sqrt{sNN} = 200 and 62.4 GeV in Au + Au and Cu + Cu collisions for K0S, phi, Lambda, Xi and Omega at STAR experiment. We focus on the recent Cu + Cu results and discuss the centrality dependence of v2 as well as the number of quark scaling as a function of transverse kinetic energy at different system size and energies. We also discuss the eccentricity scaled v2 for identified hadrons and implications that ideal hydrodynamical limit has not been reached at RHIC.