Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at s(NN)**(1/2) = 200-GeV

Abstract

We present STAR measurements of the azimuthal anisotropy parameter $v_2$ and the binary-collision scaled centrality ratio $R_{CP}$ for kaons and lambdas ($Λ+\barΛ$) at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. In combination, the $v_2$ and $R_{CP}$ particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish $p_T \approx 5$ GeV/c as the value where the centrality dependent baryon enhancement ends. The $K_S^0$ and $Λ+\barΛ$ $v_2$ values are consistent with expectations of constituent-quark-number scaling from models of hadron fromation by parton coalescence or recombination.