Azimuthal anisotropy of charged hadrons in Au+Au and Cu+Cu collisions at RHIC

The azimuthal anisotropy in particle emission is an important probe for the early dynamics of heavy-ion collisions. At RHIC, it has been well described by hydrodynamic models for transverse momenta below $\sim$ 2 GeV/c. Recombination models have been invoked to explain the baryon/meson difference and the unexpectedly high strength of the signal at intermediate $p_T$. At high $p_T$, the azimuthal asymmetry in the particle spectra can be attributed to jet quenching. The PHENIX Collaboration has recorded high statistics Au+Au and Cu+Cu collisions at center-of-mass energies in the range 62.4-200 GeV. The azimuthal anisotropy of charged hadrons obtained over a broad $p_T$ range will be presented and discussed. In particular, results from a cumulant analysis will be compared to the standard reaction plane method of flow analysis.