Up-down asymmetry: A diagnostic for neutrino oscillations

We propose a simple test of underground neutrino data to discriminate amongst neutrino oscillation models. It uses the asymmetry between downward-going events and upward-going events, for electron and muon events separately. Because of the symmetry of typical underground detectors, an asymmetry can be compared with calculations with little need for the intermediary of a simulation program. Furthermore, we show that the various oscillation scenarios give rise to dramatically differing trajectories of asymmetry versus energy for muons and electrons. This permits a clean distinction to be drawn between models.