Elliptic flow at energies available at the CERN Large Hadron Collider: Comparing heavy-ion data to viscous hydrodynamic predictions

TL;DR

This paper compares viscous hydrodynamic predictions with LHC heavy-ion collision data, finding consistency with previous RHIC-based models and emphasizing the importance of measurement subtleties for accurate data-theory comparisons.

Contribution

It provides the first viscous hydrodynamic prediction for elliptic flow at LHC energies and discusses measurement subtleties affecting data interpretation.

Findings

Data are consistent with hydrodynamic extrapolations from RHIC.

No change in medium parameters needed to match LHC data.

Highlights measurement subtleties like transverse momentum cuts and flow fluctuation sensitivities.

Abstract

I compare the first viscous hydrodynamic prediction for integrated elliptic flow in Pb-Pb collisions at the LHC with the first data released by the ALICE collaboration. These new data are found to be consistent with hydrodynamic extrapolations of RHIC data with no change in medium parameters (e.g., average viscosity). I also discuss how, in general, a precise comparison of data to theoretical calculations requires an understanding of some subtleties of the measurement -- most notably the cut on transverse momentum of the particles used and the differing sensitivities to flow fluctuations and non-flow effects of the various measurement methods.