Saturation of elliptic flow and the transport opacity of the gluon plasma at RHIC Original Research Article

Differential elliptic flow and particle spectra are calculated taking into account the finite transport opacity of the gluon plasma produced in Au+Au at View the MathML sourceGeV at RHIC. Covariant numerical solutions of the ultrarelativistic Boltzmann equation are obtained using the MPC parton cascade technique. For typical pQCD (∼3 mb) elastic cross sections, extreme initial gluon densities, View the MathML source, are required to reproduce the elliptic flow saturation pattern reported by STAR. However, we show that the solutions depend mainly on the transport opacity, View the MathML source, and thus the data can also be reproduced with dNg/dη∼1000, but with extreme elastic parton cross sections, ∼45 mb. We demonstrate that the spectra and elliptic flow are dominated by numerical artifacts unless parton subdivisions ∼100–1000 are applied to retain Lorentz covariance for RHIC initial conditions.