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Mass, quark-number, and root s(NN) dependence of the second and fourth flow harmonics in ultrarelativistic nucleus-nucleus collisions

We present STAR measurements of the azimuthal anisotropy parameter v2 for pions, kaons, protons, Lambda, [overline Lambda ], Xi+[overline Xi ], and Omega+[overline Omega ], along with v4 for pions, kaons, protons, and Lambda+[overline Lambda ] at midrapidity for Au+Au collisions at sqrt(s[sub NN])=62.4 and 200 GeV. The v2(pT) values for all hadron species at 62.4 GeV are similar to those observed in 130 and 200 GeV collisions. For observed kinematic ranges, v2 values at 62.4, 130, and 200 GeV are as little as 10– 15% larger than those in Pb+Pb collisions at sqrt(s[sub NN])=17.3 GeV. At intermediate transverse momentum (pT from 1.5– 5 GeV/c), the 62.4 GeV v2(pT) and v4(pT) 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 v2 is larger than antibaryon v2 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 v2 or that antibaryon and baryon annihilation is larger in the in-plane direction.

scattering; heavy ion gold hadron; multiple production pi K p Lambda Xi Omega- angular distribution; anisotropy transverse momentum; dependence elliptic flow impact parameter; dependence cumulant expansion baryon antibaryon; difference quark; valence scaling energy dependence collective phenomena magnetic detector; STAR experimental results Brookhaven RHIC Coll 62.4 GeV-cms/nucleon

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