Testing and improving shear viscous phase space correction models

Understand

Comparison of hydrodynamic calculations with experimental data inevitably requires a model for converting the fluid to particles.

• In this work, nonlinear $2\to 2$ kinetic theory is used to assess the overall accuracy of various shear viscous fluid-to-particle conversion models, such as the quadratic Grad corrections, the Strickland-Romatschke (SR) ansatz, self-consistent shear corrections from linearized kinetic theory, and the correction from the relaxation time approach.
• We test how well the conversion models can reconstruct, using solely the hydrodynamic fields computed from the transport, the phase space density for a massless one-component gas undergoing a 0+1D longitudinal boost-invariant expansion with approximately constant specific shear viscosity in the range $\sim 0.03 \le \eta/s \le \sim 0.2$.
• In general we find that at early times the SR form is the most accurate, whereas at late times or for small $\eta/s\sim 0.05$ the self-consistent corrections from kinetic theory perform the best.