Sensitivity of Azimuthal Jet Tomography to Early Time Energy-Loss at RHIC and LHC

TL;DR

This paper investigates how jet energy-loss sensitivity to early-time dynamics affects azimuthal harmonic measurements at RHIC and LHC, highlighting the importance of initial conditions and early evolution in jet quenching models.

Contribution

It introduces a generalized energy-loss model interpolating between pQCD and AdS/CFT, analyzing its sensitivity to early-time evolution and initial conditions in heavy-ion collisions.

Findings

High-pT second moment is sensitive to early-time evolution.

Energy and density dependence cause overquenching relative to LHC data.

Model parameters fixed at RHIC overpredict suppression at LHC.

Abstract

We compute the jet path-length dependence of energy-loss for higher azimuthal harmonics of jet-fragments in a generalized model of energy-loss that can interpolate between pQCD and AdS/CFT limits and compare results with Glauber and CGC/KLN initial conditions. We find, however, that even the high-pT second moment is most sensitive to the poorly known early-time evolution during the first fm/c. Moreover, we demonstrate that quite generally the energy and density-dependence leads to an overquenching jet fragments relative to the first LHC $R_{AA}$-data, once the parameters of the energy-loss model are fixed from $R_{AA}$-data at RHIC.