Interplay between bulk medium evolution and (D)GLV energy loss

TL;DR

This paper investigates how different bulk medium evolution models affect high-pT nuclear suppression and elliptic flow, revealing that covariant energy loss treatment can counteract flow suppression caused by transverse expansion.

Contribution

It demonstrates the impact of medium evolution models and covariant energy loss treatment on jet quenching observables, clarifying their interplay.

Findings

Hydrodynamic solutions with realistic equations of state yield lower v2.

Covariant energy loss treatment counteracts elliptic flow suppression.

Transverse expansion generally suppresses elliptic flow, but covariant effects mitigate this.

Abstract

We study the consistency between high-pT nuclear suppression (R_AA) and elliptic flow (v2) using Gyulassy-Levai-Vitev (GLV) energy loss or a simpler power-law dE/dL formula, for a variety of bulk evolution models. The results generally confirm our earlier work [arXiv:1305.1046] that found suppressed elliptic flow for transversely expanding media. One exception is the set of hydrodynamic solutions used recently [arXiv:1305.6458] by Betz and Gyulassy, which give significantly higher v2 but unfortunately assume unrealistic bag-model equation of state. On the other hand, we show that covariant treatment of energy loss introduces an interplay between jet direction and hydrodynamic flow of the medium, which largely counteracts elliptic flow suppression caused by transverse expansion.