Leading-order anisotropic hydrodynamics for central collisions

TL;DR

This paper compares leading-order anisotropic hydrodynamics with Israel-Stewart viscous hydrodynamics in modeling quark-gluon plasma evolution, highlighting differences in particle production predictions at various shear viscosity levels.

Contribution

It introduces a self-consistent anisotropic freeze-out approach and compares its results with traditional viscous hydrodynamics for different collision systems and viscosities.

Findings

Good agreement between methods at low shear viscosity (4 pi eta/s ~ 1).

Significant corrections at higher shear viscosities or in smaller collision systems.

Total charged particle number varies differently with shear viscosity in the two models.

Abstract

We use leading-order anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma. We impose a realistic lattice-based equation of state and perform self-consistent anisotropic freeze-out to hadronic degrees of freedom. We then compare our results for the full spatiotemporal evolution of the quark-gluon plasma and its subsequent freeze-out to results obtained using 1+1d Israel-Stewart second-order viscous hydrodynamics. We find that for small shear viscosities, 4 pi eta/s ~ 1, the two methods agree well for nucleus-nucleus collisions, however, for large shear viscosity to entropy density ratios or proton-nucleus collisions we find important corrections to the Israel-Stewart results for the final particle spectra and the total number of charged particles. Finally, we demonstrate that the total number of charged particles produced is a monotonically increasing function of 4 pi eta/s in Israel-Stewart viscous hydrodynamics whereas in anisotropic hydrodynamics it has a maximum at 4 pi eta/s ~ 10. For all 4 pi eta/s > 0, we find that for Pb-Pb collisions Israel-Stewart viscous hydrodynamics predicts more dissipative particle production than anisotropic hydrodynamics.