"Figure 2b-2" of "Scaling properties of azimuthal anisotropy in Au + Au and Cu + Cu collisions at s(NN)**(1/2) = 200-GeV."

Detailed differential measurements of the elliptic flow for particles produced in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200 GeV are presented. Predictions from perfect fluid hydrodynamics for the scaling of the elliptic flow coefficient $v_2$ with eccentricity, system size and transverse energy are tested and validated. For transverse kinetic energies $KE_T$ ~ $m_T$-$m$ up to ~1 GeV, scaling compatible with the hydrodynamic expansion of a thermalized fluid is observed for all produced particles. For large values of $KE_T$, the mesons and baryons scale separately. A universal scaling for the flow of both mesons and baryons is observed for the full transverse kinetic energy range of the data when quark number scaling is employed. In both cases the scaling is more pronounced in terms of $KE_T$ rather than transverse momentum.