Qualitative and Quantitative Energy Loss?

TL;DR

This paper discusses the challenges and limitations of current energy loss models in describing high-energy heavy ion collision data, highlighting the differences between pQCD and AdS/CFT approaches.

Contribution

It compares pQCD-based and AdS/CFT-based energy loss models, emphasizing their respective strengths and limitations in describing experimental observables.

Findings

pQCD models have large systematic uncertainties and cannot simultaneously describe RAA and v2.

AdS/CFT models better qualitatively match certain high-pT particle ratios.

Current models struggle to fully explain all experimental data.

Abstract

Despite the 300% systematic theoretical uncertainty associated with extracting qhat using current energy loss models due to the collinear approximation, and despite the uncertainties in the initial geometry and corrections due to the fluctuations in the initial overlap of a heavy ion collision, a simultaneous description of high-pT pi^0 RAA and v2 is not possible with current pQCD-based energy loss models. However a good description of out-of-plane RAA as a function of centrality is possible. Alternatively, energy loss models based on AdS/CFT give a better qualitative description of pi^0 and non-photonic electron RAA as well as high-pT ratios of antiprotons to pi^- production than those based on pQCD.