Jets in medium - what RHIC and LHC measurements of R_AA and I_AA can teach about the parton-medium interaction

TL;DR

This paper discusses how measurements of jet quenching at RHIC and LHC can inform us about the microscopic interactions between high-energy partons and the quark-gluon plasma, highlighting the importance of systematic comparisons of multiple observables.

Contribution

It demonstrates that a comprehensive comparison of various jet quenching observables can effectively constrain models of parton-medium interactions, favoring perturbative radiation mechanisms.

Findings

Perturbative medium-induced radiation is the dominant interaction mechanism.

Elastic energy transfer plays a minor role.

Systematic multi-observable analysis rules out many models.

Abstract

High P_T observables associated with hard pQCD processes are regarded as tomographic probes of the medium created in ultrarelativistic heavy-ion collisions. Unfortunately, tomography is unexpectedly complicated in practice due to model uncertainties and the highly averaged nature of many observables. However, a systematic comparison study demanding a simultaneous description of many observables within the same framework is sufficiently powerful to rule out a large fraction of conjectured models about the physics mechanism of parton-medium interaction. From this study, it can be inferred that the relevant mechanism is likely to be perturbatively tractable medium-induced radiation with a small component of elastic energy transfer into the medium.