Flow dependence of high $p_T$ parton energy loss in heavy-ion collisions

Abstract

The measured transverse momentum spectra and HBT correlations of bulk (i.e. low $p_T$) matter can be well explained by assuming that the soft sector of particles produced in ultrarelativistic heavy-ion collisions is (approximately) thermalized and undergoes collective accelerated expansion in both longitudinal and transverse direction. However, this implies that bulk matter will have a non-vanishing flow component transverse to the trajectory of a high $p_T$ partonic jets. In general, this will increase the energy loss experienced by the jet parton and modify the shape of the jet cone. In this paper, we present a systematic study of the magnitude of the additional energy loss induced by flow under realistic assumptions for the medium evolution. We argue that a perturbative QGP description may be sufficient for the measured $R_{AA}$ if flow during the medium evolution is taken into account properly.