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

## TL;DR

This paper introduces a Monte-Carlo model to compute elastic energy loss of high-energy partons in a hydrodynamical medium, based on pQCD interactions, serving as a baseline for understanding parton-medium interactions in heavy-ion collisions.

## Contribution

The model combines pQCD cross sections with hydrodynamical medium evolution, including non-eikonal effects and parton conversions, providing a novel baseline for elastic energy loss calculations.

## Key findings

- Provides a Monte-Carlo framework for elastic energy loss in a hydrodynamical medium.
- Accounts for exact energy-momentum conservation and parton conversions.
- Establishes a baseline for future studies of medium effects on high-$P_T$ partons.

## 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 Quantum Chromodynamics (pQCD) cross sections for $2\to 2$ 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, non-eikonal 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 more sophisticated medium description, as well as inclusion of higher-order processes and coherence effects in the pQCD scatterings.