title: Elliptic flow and nuclear modification factor in ultrarelativistic heavy-ion collisions within a partonic transport model.
abstract: The quark gluon plasma produced in ultrarelativistic heavy-ion collisions exhibits remarkable features. It behaves like a nearly perfect liquid with a small shear viscosity to entropy density ratio and leads to the quenching of highly energetic particles. We show that both effects can be understood for the first time within one common framework. Employing the parton cascade Boltzmann approach to multiparton scatterings, the microscopic interactions and the space-time evolution of the quark gluon plasma are calculated by solving the relativistic Boltzmann equation. Based on cross sections obtained from perturbative QCD with explicitly taking the running coupling into account, we calculate the nuclear modification factor and elliptic flow in ultrarelativistic heavy-ion collisions. With only one single parameter associated with coherence effects of medium-induced gluon radiation, the experimental data of both observables can be understood on a microscopic level. Furthermore, we show that perturbative QCD interactions with a running coupling lead to a sufficiently small shear viscosity to entropy density ratio of the quark gluon plasma, which provides a microscopic explanation for the observations stated by hydrodynamic calculations.
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Uphoff
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Senzel
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Fochler
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wesp
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt am Main, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Greiner