Hadron spectra and elliptic flow for 200 A GeV Au+Au collisions from viscous hydrodynamics coupled to a Boltzmann cascade

TL;DR

The paper demonstrates that the hybrid VISHNU model, combining viscous hydrodynamics and a Boltzmann cascade, accurately reproduces hadron spectra and elliptic flow in 200 A GeV Au+Au collisions at RHIC, accounting for initial fluctuations and shear viscosity.

Contribution

It introduces and validates the VISHNU hybrid code as an effective tool for modeling QGP evolution and hadronic rescattering in heavy-ion collisions.

Findings

Excellent agreement with experimental spectra and elliptic flow data.

Universal description across collision centralities.

Consistent extraction of shear viscosity from data.

Abstract

It is shown that the recently developed hybrid code VISHNU, which couples a relativistic viscous fluid dynamical description of the quark-gluon plasma (QGP) with a microscopic Boltzmann cascade for the late hadronic rescattering stage, yields an excellent description of charged and identified hadron spectra and elliptic flow measured in 200 A GeV Au+Au collisions at the Relativistic Heavy-Ion Collider (RHIC). Using initial conditions that incorporate event-by-event fluctuations in the initial shape and orientation of the collision fireball and values eta/s for the specific shear viscosity of the quark-gluon plasma that were recently extracted from the measured centrality dependence of the eccentricity-scaled, p_T-integrated charged hadron elliptic flow, we obtain universally good agreement between theory and experiment for the p_T-spectra and differential elliptic flow v_2(p_T) for both pions and protons at all collision centralities.