# Constraining energy loss from high-$p_{\rm T}$ azimuthal asymmetries

## TL;DR

This paper demonstrates that accurately modeling high-$p_{T}$ azimuthal asymmetries and $R_{AA}$ requires suppressing jet quenching in the initial 0.6 fm, highlighting the importance of early-stage dynamics in heavy-ion collisions.

## Contribution

It introduces a method to better constrain initial-stage energy loss by adjusting jet quenching models to match high-$p_{T}$ azimuthal asymmetries and $R_{AA}$.

## Key findings

- Suppression of quenching in the first 0.6 fm improves model accuracy.
- High-$p_{T}$ azimuthal asymmetries are sensitive to early-stage dynamics.
- Models underpredict high-$p_{T}$ elliptic flow without early suppression.

## Abstract

The nuclear modification factor $R_{\rm AA}$ has been satisfactorily described by various jet quenching models. Nonetheless, all these formalisms, until very recently, underpredicted the high-$p_{\rm T}$ (> 10 GeV) elliptic flow $v_2$. We find that the simultaneous description of these observables requires to strongly suppress the quenching for the first $\sim 0.6$ fm after the collision. This shows the potential of jet quenching observables to constrain the dynamics of the initial stages of the evolution.