Mass, quark-number, and root s(NN) dependence of the second and fourth flow harmonics in ultrarelativistic nucleus-nucleus collisions
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We present STAR measurements of the azimuthal anisotropy parameter v(2) for pions, kaons, protons, Lambda,(Lambda) over bar,Xi+ (Xi) over bar, and Omega+ (Omega) over bar, along with v(4) for pions, kaons, protons, and Lambda+(Lambda) over bar at midrapidity for Au+Au collisions at root s(NN)=62.4 and 200 GeV. The v(2)(p(T)) values for all hadron species at 62.4 GeV are similar to those observed in 130 and 200 GeV collisions. For observed kinematic ranges, v(2) values at 62.4, 130, and 200 GeV are as little as 10-15% larger than those in Pb+Pb collisions at root s(NN)=17.3 GeV. At intermediate transverse momentum (p(T) from 1.5-5 GeV/c), the 62.4 GeV v(2)(p(T)) and v(4)(p(T)) values are consistent with the quark-number scaling first observed at 200 GeV. A four-particle cumulant analysis is used to assess the nonflow contributions to pions and protons and some indications are found for a smaller nonflow contribution to protons than pions. Baryon v(2) is larger than antibaryon v(2) at 62.4 and 200 GeV, perhaps indicating either that the initial spatial net-baryon distribution is anisotropic, that the mechanism leading to transport of baryon number from beam- to midrapidity enhances v(2) or that antibaryon and baryon annihilation is larger in the in-plane direction.