Formula omitted] azimuthal anisotropy in Au+Au collisions at [formula omitted] from PHENIX: collision energy and path-length dependence of jet-quenching and the role of initial geometry

Abstract

The azimuthal anisotropy of high p T particle production in heavy ion collisions is a sensitive probe of the jet quenching mechanism. Recent PHENIX measurements for Au+Au collisions at s N N = 200 GeV show a π 0 v 2 signal that exceeds the pQCD energy loss calculations up to p T ∼ 10 GeV/c , challenging the traditional perturbative picture of the energy loss process. Here, we present an update and details of that measurement, as well as new high p T measurements at s N N = 62 and 39 GeV. These measurements not only provide an important constraint for understanding the path-length dependence of jet energy loss and the role of initial collision geometry, but also allow a search for the onset of jet quenching as s N N is varied.