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Charged and strange hadron elliptic flow in Cu+Cu collisions at $\sqrt{; ; ; s_{; ; ; NN}; ; ; }; ; ; $ = 62.4 and 200 GeV

We present the results of an elliptic flow analysis of Cu+Cu collisions recorded with the STAR detector at 62.4 and 200GeV. Elliptic flow as a function of transverse momentum is reported for different collision centralities for charged hadrons and strangeness containing hadrons $K_{; ; ; S}; ; ; ^{; ; ; 0}; ; ; $, $\Lambda$, $\Xi$, $\phi$ in the midrapidity region $|eta|<1.0$. Significant reduction in systematic uncertainty of the measurement due to non-flow effects has been achieved by correlating particles at midrapidity, $|\eta|<1.0$, with those at forward rapidity, $2.5<|\eta|<4.0$. We also present azimuthal correlations in p+p collisions at 200 GeV to help estimating non-flow effects. To study the system-size dependence of elliptic flow, we present a detailed comparison with previously published results from Au+Au collisions at 200 GeV. We observe that $v_{; ; ; 2}; ; ; $($p_{; ; ; T}; ; ; $) of strange hadrons has similar scaling properties as were first observed in Au+Au collisions, i.e.: (i) at low transverse momenta, $p_T<2GeV/c$, $v_{; ; ; 2}; ; ; $ scales with transverse kinetic energy, $m_{; ; ; T}; ; ; -m$, and (ii) at intermediate $p_T$, $2<p_T<4GeV/c$, it scales with the number of constituent quarks, $n_q$. We have found that ideal hydrodynamic calculations fail to reproduce the centrality dependence of $v_{; ; ; 2}; ; ; $($p_{; ; ; T}; ; ; $) for $K_{; ; ; S}; ; ; ^{; ; ; 0}; ; ; $ and $\Lambda$. Eccentricity scaled $v_2$ values, $v_{; ; ; 2}; ; ; /\epsilon$, are larger in more central collisions, suggesting stronger collective flow develops in more central collisions. The comparison with Au+Au collisions which go further in density shows $v_{; ; ; 2}; ; ; /\epsilon$ depend on the system size, number of participants $N_{; ; ; part}; ; ; $. This indicates that the ideal hydrodynamic limit is not reached in Cu+Cu collisions, presumably because the assumption of thermalization is not attained.

heavy ion; scattering copper charged particle; elliptic flow copper strange particle; elliptic flow fermion number particle flow; collective phenomena transverse momentum; dependence impact parameter; dependence hydrodynamics angular correlation rapidity; correlation STAR scaling experimental results Brookhaven RHIC Coll 62.4; 200.0 GeV-cms/nucleon

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