Building a testable shear viscosity across the QCD phase diagram

Abstract

Current experiments at the Relativistic Heavy Ion Collider (RHIC) are probing finite baryon densities where the shear viscosity to enthalpy ratio $\ensuremath{\eta}T/w$ of the quark gluon plasma remains unknown. We use the hadron resonance gas (HRG) model with the most up-to-date hadron list to calculate $\ensuremath{\eta}T/w$ at low temperatures and at finite baryon densities ${\ensuremath{\rho}}_{B}$. We then match $\ensuremath{\eta}T/w$ to a quantum-chromodynamics-based shear viscosity calculation within the deconfined phase to create a table across ${T,{\ensuremath{\mu}}_{B}}$ for different crossover and critical point scenarios at a specified location. We find that these new $\ensuremath{\eta}T/w(T,{\ensuremath{\mu}}_{B})$ values would require initial conditions at significantly larger ${\ensuremath{\rho}}_{B}$, compared to ideal hydrodynamic trajectories, to reach the same freeze-out point.