Monte-Carlo model for elastic energy loss in a hydrodynamical background

Abstract

We present a computation of elastic energy loss of hard partons traversing the bulk hydrodynamical medium created in ultrarelativistic heavy-ion collisions. The model is based on perturbative QCD (pQCD) cross sections for $2\ensuremath{\rightarrow}2$ processes in which a hard incoming parton is assumed to interact with a thermal parton from the medium. We model the interactions of this type in a Monte-Carlo framework to account properly for exact energy-momentum conservation, noneikonal parton propagation, parton conversion reactions, and the possibility to create additional hard recoiling partons from the medium. For the thermodynamical properties of the medium we use a hydrodynamical evolution model. We do not aim at a full description of high transverse momentum (${P}_{T}$) observables at this point. Rather, we view the model as a starting point in obtaining a baseline of what to expect under the assumptions that the medium is describable by thermal quasifree partons and that their pQCD interactions with the high-energy partons are independent. Deviations from this baseline then call for a more sophisticated medium description, as well as inclusion of higher-order processes and coherence effects in the pQCD scatterings.