Neutrino Mass Difference Induced Oscillations in Observed Muon Decays
  The recent real time KARMEN anomaly for the electron neutrino counting rates (obtained from stopped muon decays) is analyzed by employing a neutrino flavor rotation model in which the muon neutrino is in a superposition of only two mass eigenstates. On the basis of experimental electron neutrino counting oscillations, we find a neutrino mass splitting $|m_2^2-m_1^2|=(0.22\pm 0.02)(eV/c^2)^2$ and a flavor rotation angle $\phi =0.34\pm 0.10$, both within a 95% confidence interval. 
Y. N. Srivastava, S. Palit, A.Widom and E. Sassaroli