Physics Letters B (Jun 2021)
A first estimate of η/s in Au+Au reactions at Elab = 1.23 AGeV
Abstract
The HADES experiment at GSI has recently provided data on the flow coefficients v1,...,v4 for protons in Au+Au reactions at Elab=1.23AGeV (or sNN=2.4GeV). This data allows to estimate the shear viscosity over entropy density ratio, η/s at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of η/s≈0.65±0.15 (or (8±2)(4π)−1) at such low energies.