System Size and Energy Dependence of Elliptic Flow

Abstract

The elliptic flow v2 is presented for the Cu+Cu collisions at sqrt{s_NN} = 62.4 and 200 GeV, as a function of pseudorapidity. Comparison to results for the Au+Au collisions at the same energies shows a reduction of about 20% in the flow observed for a centrality selection of 0-40%. The centrality dependent flow, expressed as a function of the number of participants N_part, is compared for the Cu+Cu and Au+Au systems using two definitions of eccentricity, the standard definition epsilon_standard and a participant eccentricity epsilon_part. The v2 / <epsilon_part> as a function of N_part, for the Au+Au and Cu+Cu collisions are consistent within errors, while v2 / <epsilon_standard> gives unrealistically large values for Cu+Cu, especially for central collision.