Saturation of azimuthal anisotropy in Au + Au collisions at s(NN)**(1/2) = 62-GeV - 200-GeV.

The PHENIX collaboration
Adler, S.S. , Afanasiev, S. , Aidala, C. , Ajitanand, N.N. , Akiba, Y. , Al-Jamel, A. , Alexander, J. , Amirikas, R. , Aoki, K. , Aphecetche, L.
Phys.Rev.Lett. 94 (2005) 232302, 2005.

Abstract (data abstract)
New measurements are presented for charged hadron azimuthal correlations at mid-rapidity in Au+Au collissions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV. They are compared to earlier measurements obtained at $\sqrt{s_{NN}}$ = 130 GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 17.2 GeV. Sizeable anisotropies are observed with centrality and transverse momentum ($p_T$) dependence characteristic of elliptic flow ($v_2$). For a broad range of centralities, the observed magnitudes and trends of the differential anisotropy, $v_2$($p_T$), change very little over the collision energy range $\sqrt{s_{NN}}$ = 62-200 GeV, indicating saturation of the excitation function for $v_2$ at these energies. Sucha a saturation may be indicative of the dominance of a very soft equation of state for $\sqrt{s_{NN}}$ ~ 60-200 GeV.

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