3+1 dimensional viscous hydrodynamics at high baryon densities

We apply a 3+1D viscous hydrodynamic + cascade model to heavy ion collision reactions with = 6.3... 39 GeV. To accommodate the model for a given collision energy range, the initial conditions for the hydrodynamic phase are taken from UrQMD, and the equation of state at finite baryon density is based on a Chiral model coupled to the Polyakov loop.

We study the collision energy dependence of pion and kaon rapidity distributions and m_T-spectra, as well as charged hadron elliptic flow and how shear viscosity affects them. The model calculations are compared to the data for Pb-Pb collisions at CERN SPS, as well as for Au-Au collisions in the Beam Energy Scan (BES) program energies at BNL RHIC. The data favours the value of shear viscosity η/s gtrsim 0.2 for this collision energy range.