We report measurements of charged particle elliptic flow %($v_2$) at mid-rapidity in Au+Au and Cu+Cu collisions at $\sqrt{ s_{ _{ NN}}}=62$ and 200 GeV. Using correlations between main STAR TPC and Forward TPCs ensures minimal bias due to non-flow effects. We further investigate the effect of flow fluctuations on $v_2/\eps$ scaling studying initial geometry eccentricity fluctuations in Monte-Carlo Glauber model, consistent with STAR direct measurements of elliptic flow fluctuations. It is found that accounting for the effect of flow fluctuations improves $v_2/\eps$ scaling.
Categories: nucl-ex