The Mont Blanc mystery solved? A $m^2=-0.28 keV^2$ neutrino

Evidence is presented in support of a hypothesis made in 2013 predicting the existence of a tachyonic neutrino mass eigenstate doublet having $m^2\approx -0.2 keV^2$ with $\Delta m^2=1 eV^2.$ The evidence is based primarily on the puzzling LSD (Mont Blanc) neutrino burst observed on February 23, 1987, which the hypothesis thoroughly explains, with additional support from the Kamiokande-II events recorded on the same day. The probability of the null hypothesis, i.e., that background fluctuations can explain the noted features of the two data sets is estimated to be $4.2\sigma$ (Mont Blanc), and $3.7\sigma$ (K-II). Such a controversial hypothesis as a tachyonic neutrino requires absolutely definitive proof, and there may exist a test based on observing the neutrino spectrum from diffuse supernovae that could supply it.