Quenching and Tomography from RHIC to LHC

TL;DR

This paper compares perturbative and nonperturbative models of high-pT energy loss in heavy-ion collisions, showing both can describe experimental data from RHIC and LHC, and proposes a new observable to distinguish these models.

Contribution

It provides a comparative analysis of pQCD and AdS/CFT energy loss models against recent LHC data and introduces the charm to bottom quark RAA ratio as a discriminating observable.

Findings

pQCD predictions describe LHC data well when constrained by RHIC data

AdS/CFT models also qualitatively match suppression patterns

The charm/bottom RAA ratio can differentiate energy loss mechanisms

Abstract

We compare fully perturbative and fully nonperturbative pictures of high-pT energy loss calculations to the first results from LHC. While over-suppressed compared to published ALICE data, parameter-free pQCD predictions based on the WHDG energy loss model constrained to RHIC data simultaneously describe well the preliminary CMS hadron suppression, ATLAS charged hadron v2, and ALICE D meson suppression; we also provide for future reference WHDG predictions for B meson RAA. However, energy loss calculations based on AdS/CFT also qualitatively describe well the RHIC pion and non-photonic electron suppression and LHC charged hadron suppression. We propose the double ratio of charm to bottom quark RAA will qualitatively distinguish between these two energy loss pictures.