Quasiparticle anisotropic hydrodynamics for central collisions

TL;DR

This paper applies quasiparticle anisotropic hydrodynamics to model a quark-gluon plasma, comparing it with standard methods, and finds it avoids unphysical results at high shear viscosity, providing more realistic particle spectra.

Contribution

It introduces a quasiparticle anisotropic hydrodynamics framework with a realistic equation of state and compares its results to standard methods, highlighting its advantages at high viscosities.

Findings

All methods agree at low shear viscosity.

Standard viscous hydrodynamics can produce negative spectra at high p_T.

Quasiparticle anisotropic hydrodynamics avoids unphysical negative spectra.

Abstract

We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative at large p_T which is clearly unphysical. Such a behavior is not seen in either anisotropic hydrodynamics approach, irrespective of the value of eta/s.