Rapidity correlations test stochastic hydrodynamics

We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time τπ that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity ν = η/sT. We formulate methods for computing these correlations using second order dissipative hydrodynamics with noise. Current data are consistent with τπ/ν ~ 10 but targeted measurements can improve this precision.