Varying and inverting the mass hierarchy in collisional energy loss

TL;DR

This paper explores how the mass hierarchy of collisional energy loss in QCD media can be altered or inverted by changing medium properties, offering new ways to distinguish between radiative and collisional jet quenching mechanisms.

Contribution

It demonstrates that the mass hierarchy of collisional energy loss depends on medium properties and can be significantly modified or inverted, unlike radiative energy loss.

Findings

Mass hierarchy of collisional energy loss can be inverted.

Medium properties significantly influence collisional energy loss.

Potential to disentangle radiative and collisional jet quenching contributions.

Abstract

Heavy ion collisions at RHIC and at the LHC give access to the medium-induced suppression patterns of heavy-flavored single inclusive hadron spectra at high transverse momentum. This opens novel opportunities for a detailed characterization of the medium produced in the collision. In this note, we point out that the capacity of a QCD medium to absorb the recoil of a partonic projectile is an independent signature, which may differ for different media at the same density. In particular, while the mass hierarchy (i.e., the projectile mass dependence) of radiative energy loss depends solely on a property of the projectile, the mass hierarchy of collisional energy loss depends significantly on properties of the medium. By varying these properties in a class of models, we find that the mass hierarchy of collisional parton energy loss can be modified considerably and can even be inverted, compared to that of radiative parton energy loss. This may help to disentangle the relative strengths of radiative and collisional contributions to jet quenching, and it may be employed to constrain properties of the produced QCD medium beyond its density.