52 research outputs found
Estimation of the shear viscosity at finite net-baryon density from A+A collision data at GeV
Hybrid approaches based on relativistic hydrodynamics and transport theory
have been successfully applied for many years for the dynamical description of
heavy ion collisions at ultrarelativistic energies. In this work a new viscous
hybrid model employing the hadron transport approach UrQMD for the early and
late non-equilibrium stages of the reaction, and 3+1 dimensional viscous
hydrodynamics for the hot and dense quark-gluon plasma stage is introduced.
This approach includes the equation of motion for finite baryon number, and
employs an equation of state with finite net-baryon density to allow for
calculations in a large range of beam energies. The parameter space of the
model is explored, and constrained by comparison with the experimental data for
bulk observables from SPS and the phase I beam energy scan at RHIC. The favored
parameter values depend on energy, but allow to extract the effective value of
the shear viscosity coefficient over entropy density ratio in the
fluid phase for the whole energy region under investigation. The estimated
value of increases with decreasing collision energy, which may
indicate that of the quark-gluon plasma depends on baryochemical
potential .Comment: minor changes in the text, results for constant eta*T/w added.
Version accepted for publication in Phys. Rev.
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