A systematic comparison of jet quenching in different fluid-dynamical models

TL;DR

This study compares different hydrodynamic models and energy loss mechanisms to understand jet quenching effects in heavy-ion collisions, finding that models delaying energy loss better match experimental data on emission-angle dependence.

Contribution

It systematically evaluates ideal and viscous hydrodynamic models combined with various energy loss models to improve understanding of jet quenching in heavy-ion collisions.

Findings

Models delaying energy loss better reproduce in-plane vs. out-of-plane R_AA(phi)

Viscous heating in hydrodynamics improves medium density evolution

No clear advantage found for I_AA(phi) over R_AA(phi) in tomography

Abstract

Comparing four different (ideal and viscous) hydrodynamic models for the evolution of the medium created in 200 AGeV Au-Au collisions, combined with two different models for the path length dependence of parton energy loss, we study the effects of jet quenching on the emission-angle dependence of the nuclear suppression factor R_AA(phi) and the away-side per trigger yield I_AA(phi). Each hydrodynamic model was tuned to provide a reasonable description of the single-particle transverse momentum spectra for all collision centralities, and the energy loss models were adjusted to yield the same pion nuclear suppression factor in central Au-Au collisions. We find that the experimentally measured in-plane vs. out-of-plane spread in R_AA(phi) is better reproduced by models that shift the weight of the parton energy loss to later times along its path. Among the models studied here, this is best achieved by energy loss models that suppress energy loss at early times, combined with hydrodynamic models that delay the dilution of the medium density due to hydrodynamic expansion by viscous heating. We were unable to identify a clear tomographic benefit of a measurement of I_AA(phi) over that of R_AA(phi).