Particle dependence of elliptic flow in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV

Abstract

The elliptic flow parameter ($v_2$) for $K_S^0$ and $Λ+\barΛ$ has been measured at mid-rapidity in Au + Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV by the STAR collaboration. The $v_2$ values for both $K_S^{0}$ and $Λ+\barΛ$ saturate at moderate $p_T$, deviating from the hydrodynamic behavior observed in the lower $p_T$ region. The saturated $v_2$ values and the $p_T$ scales where the deviation begins are particle dependent. The particle-type dependence of $v_2$ shows features expected from the hadronization of a partonic ellipsoid by coalescence of co-moving quarks. These results will be discussed in relation to the nuclear modification factor ($R_{CP}$) which has also been measured for $K_S^0$ and $Λ+\barΛ$ by the STAR collaboration.