A Summary of Bulk Dynamics from Quark Matter 2009

TL;DR

This paper reviews recent advances in understanding elliptic flow in heavy ion collisions, highlighting the transition from kinetic to hydrodynamic regimes and the role of shear viscosity in modeling the data.

Contribution

It provides a comprehensive overview of how hydrodynamics describes elliptic flow development and discusses methods to extract shear viscosity from experimental measurements.

Findings

Hydrodynamics develops as system size increases from peripheral to central collisions.

Including shear viscosity reproduces deviations from ideal hydrodynamics.

Hydrodynamic predictions for LHC are discussed.

Abstract

I review the recent progress in measuring elliptic flow in heavy ion collisions. These measurements show clearly how hydrodynamics starts to develop as the system size is increased from peripheral to central collisions. During this transition, the momentum range described by hydrodynamics increases as the system progresses from a kinetic to a hydrodynamic regime. Many of the systematic deviations from ideal hydrodynamics are reproduced effortlessly once the shear viscosity is included. In order to extract the shear viscosity from the data, kinetic theory can be used to determine which aspects of the elliptic flow reflect the details of the microscopic interactions, and which aspects reflect the underlying transport coefficients. I also review the identified hadron elliptic flow and the predictions of hydrodynamics for the LHC.