  We investigate the collision energy dependence of $\eta/s$ in a transport +
viscous hydrodynamics hybrid model. A Bayesian analysis is performed on RHIC
beam energy scan data for $Au+Au$ collisions at $\sqrt{s_{NN}}=19.6,39,$ and
$62.4$ GeV. The resulting posterior probability distributions for the model
parameters show a preference for a larger value of $\eta/s$ at $19.6$ GeV
compared to $62.4$ GeV, indicating dependence on baryon chemical potential
$\mu_B$.
