The Phenomenology of Elastic Energy Loss

TL;DR

This paper examines the role of elastic energy loss in heavy-ion collisions, showing that models with linear pathlength dependence are inconsistent with experimental data, implying elastic losses are minimal.

Contribution

It introduces a class of energy loss models with linear pathlength dependence and tests their compatibility with experimental data, challenging the significance of elastic energy loss.

Findings

Models with linear pathlength dependence are incompatible with data.

Elastic energy loss must be small to match observations.

Radiative energy loss dominates in the studied scenarios.

Abstract

The unexpectedly strong suppression of high p_T heavy-quarks in heavy-ion collisions has given rise to the idea that partons propagating through a medium in addition to energy loss by induced radiation also undergo substantial energy loss due to elastic collisions. However, the precise magnitude of this elastic energy loss component is highly controversial. While it is for a parton inside a medium surprisingly difficult to define the difference between elastic and radiative processes rigorously, the main phenomenological difference is in the dependence of energy loss on in-medium pathlength: in a constant medium radiative energy loss is expected to grow quadratically with pathlength, elastic energy loss linearly. In this paper, we investigate a class of energy loss models with such a linear pathlength dependence and demonstrate that they are incompatible with measured data on hard hadronic back-to-back correlations where a substantial variation of pathlength is probed. This indicates that any elastic energy loss component has to be small.