Can Long-Baseline Neutrino Oscillation Experiments Tell Us about Neutrino Dark Matter?

Abstract

We define the ratio R = (No. of observed electron events)/ (No. of expected muon events - No. of observed muon events) as a measure for relative importance of $\nu_\mu \to \nu_e$ and $\nu_\mu \to \nu_\tau$ oscillations which will be measurable in coming long-baseline neutrino experiments. We then argue that if neutrino oscillation is observed with 0.02 < R < 0.87 it implies the rejection of the neutrino dark matter hypothesis. Our argument is valid if neutrinos come with only three flavors without steriles and if they have a hierarchical mass pattern.