Fluctuating Initial Conditions and Anisotropic Flows

In this work we study the connection between anisotropic flows and lumpy initial conditions for Au+Au collisions at 200GeV. We present comparisons between anisotropic flow coefficients and eccentricities up to sixth order, and between initial condition reference angles and azimuthal particle distribution angles. We also present a toy model to justify the lack of connection between flow coefficients and eccentricities for individual events.Comment: 5 pages, 3 figure

Anisotropic flow in event-by-event ideal hydrodynamic simulations of sqrt(s_{NN})=200 GeV Au+Au collisions

We calculate flow observables with the NeXSPheRIO ideal hydrodynamic model and make the first comparison to the complete set of mid-rapidity flow measurements made by the PHENIX collaboration in top energy Au+Au collisions. A simultaneous calculation of v_2, v_3, v_4, and the first event-by-event calculation of quadrangular flow defined with respect to the v_2 event plane (v_4{Psi_2}) gives good agreement with measured values, including the dependence on both transverse momentum and centrality. This provides confirmation that the collision system is indeed well described as a quark-gluon plasma with an extremely small viscosity, and that correlations are dominantly generated from collective effects. In addition we present a prediction for v_5.Comment: 5 pages, 2 figures. Revised version. Corrections in eq.(7) and Fig.

Linear and cubic response to the initial eccentricity in heavy-ion collisions

We study the relation between elliptic flow, $v_2$ and the initial eccentricity, $\varepsilon_2$, in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.Comment: 7 pages. v2: bugs corrected in Figs.1,2,4,5, text unchange

Directed flow at mid-rapidity in event-by-event hydrodynamics

Fluctuations in the initial geometry of a nucleus-nucleus collision have been recently shown to result in a new type of directed flow (v_1) that, unlike the usual directed flow, is also present at midrapidity. We compute this new v_1 versus transverse momentum and centrality for Au-Au collisions at RHIC using the hydrodynamic code NeXSPheRIO. We find that the event plane of v_1 is correlated with the angle of the initial dipole of the distribution, as predicted, though with a large dispersion. It is uncorrelated with the reaction plane. Our results are in excellent agreement with results inferred from STAR correlation data.Comment: 7 pages, 6 figures; Figure data files included with source; Version accepted for publication (minor changes