Resolving the $R_{AA}$ to $v_n$ puzzle

TL;DR

Recent advances in theoretical modeling have enabled simultaneous accurate descriptions of $R_{AA}$ and $v_n$ at high transverse momentum, incorporating event-by-event fluctuations and new experimental observables.

Contribution

The paper reviews key theoretical developments and introduces Soft Hard Event Engineering as a novel observable for studying energy loss path length dependence.

Findings

Models now reproduce $R_{AA}$ and $v_n$ data well

Event-by-event fluctuations are crucial for accurate modeling

SHEE observables are sensitive to energy loss mechanisms

Abstract

After 10 years of struggling to simultaneously describe the nuclear modification factor $R_{AA}$ and flow harmonics $v_n$'s at high $p_T$, now theoretical models are able to reproduce experimental data well. The necessary theoretical developments such as event-by-event fluctuations, choice of initial conditions, and the scalar product method to calculate flow harmonics at high $p_T$ are reviewed. Additionally, a discussion of new proposed experimental observables known as Soft Hard Event Engineering (SHEE) that are sensitive to the path length dependence of the energy loss is included.