Comparison of radiative energy loss models in a hot QCD medium

TL;DR

This paper compares two models of radiative energy loss in a hot QCD medium, highlighting differences and effects of medium inhomogeneity on predictions of high-energy parton suppression.

Contribution

It provides a side-by-side comparison of the ASW-MS and opacity expansion formalisms using a common medium profile, addressing discrepancies in coupling strength estimates.

Findings

Equivalent brick models overestimate energy loss for long trajectories

Medium inhomogeneity influences energy loss predictions

Models show significant differences in coupling estimates

Abstract

The suppression of high $p_{T}$ hadron production in heavy ion collisions is thought to be due to energy loss by gluon radiation off hard partons in a QCD medium. Existing models of QCD radiative energy loss in a color-charged medium give estimates of the coupling strength of the parton to the medium which differ by a factor of $5$. We will present a side-by-side comparison of two different formalisms to calculate the energy loss of light quarks and gluons: the multiple soft scattering approximation (ASW-MS) and the opacity expansion formalism (ASW-SH and WHDG-rad). A common time-temperature profile is used to characterize the medium. The results are compared to the single hadron suppression $R_{AA}$ at RHIC energies. In addition the influcence of homogeneous and non-homogeneous distribution of scattering centers is discussed. We find that using an equivalent brick overestimates the energy loss for long parton trajectories.