# Extracting $\hat{q}$ in event-by-event hydrodynamics and the centrality/energy puzzle

## TL;DR

This paper combines event-by-event hydrodynamics with jet quenching models to analyze high-$p_T$ particle suppression at RHIC and LHC, revealing a centrality-independent $K$-factor that measures deviations of $t$ from ideal estimates.

## Contribution

It introduces a novel $K$-factor to quantify the deviation of $t$ from ideal estimates and applies it across different energies and centralities in heavy-ion collisions.

## Key findings

- $K$-factor is larger at RHIC than LHC.
- $K$-factor is nearly independent of collision centrality.
- The analysis provides a unified description of high-$p_T$ suppression data.

## Abstract

In our analysis, we combine event-by-event hydrodynamics, within the EKRT formulation, with jet quenching -ASW Quenching Weights- to obtain high-$p_T$ $R_{\rm AA}$ for charged particles at RHIC and LHC energies for different centralities. By defining a $K$-factor that quantifies the departure of $\hat{q}$ from an ideal estimate, $K = \hat{q}/(2\epsilon^{3/4})$, we fit the single-inclusive experimental data for charged particles. This $K$-factor is larger at RHIC than at the LHC but, surprisingly, it is almost independent of the centrality of the collision.