Neutrino Decay as an Explanation of Atmospheric Neutrino Observations
  We show that the observed zenith angle dependence of the atmospheric neutrinos can be accounted for by neutrino decay. Furthermore, it is possible to account for all neutrino anomalies with just three flavors. 
V.Barger, J.G. Learned, S. Pakvasa, and T.J. Weiler