Centrality dependence of charged hadron and strange hadron elliptic flow from [v]sNN = 200 GeV Au + Au collisions

The event azimuthal anisotropy with respect to the reaction plane has been widely studied in order to evaluate the collective behavior of the matter produced in high-energy nuclear collisions [1, 2, 3]. The initial configuration space anisotropy is expected to be self-quenched by expansion and reduced by frequent re-scatterings in the hot and dense medium created in such collisions. The final observed momentum space anisotropies, therefore, carry information about the early stage collision dynamics [4, 5, 6]. The experimental results of the second harmonic azimuthal anisotropy, elliptic flow, v2, from Au + Au collisions have demonstrated the development of partonic collectivity [7, 8, 9, 10]. Further detailed analyses of the hadron mass dependence of v2 suggest that the system has been in the deconfined state with constituent quark degrees of freedom prior to hadronization [11, 12, 13]. Furthermore, results of multi-strange hadron transverse momentum distributions and v2 indicate that the system reached thermalization at the partonic stage [14, 15, 16, 17].