The Mont Blanc neutrinos from SN 1987A: Could they have been monochromatic (8 MeV) tachyons with $m^2=-0.38$ keV$^2$?

Abstract

Here we consider faster-than-light neutrinos having $m_ν^2=-0.38$ $keV^2$ as the explanation of the Mont Blanc burst. It is shown that the Mont Blanc burst is consistent with the distinctive signature of that explanation i.e., an 8 MeV antineutrino line from SN 1987A. It is further shown that a model of core collapse supernovae involving dark matter particles of mass 8 MeV would in fact yield an 8 MeV antineutrino line. Moreover, that dark matter model predicts 8 MeV $ν,\barν$ and $e^+e^-$ pairs from the galactic center, a place where one would expect large amounts of dark matter to collect. The resulting $e^+$ would create $γ-$rays from the galactic center, and a fit to MeV $γ-$ray data yields the model's dark matter mass, as well as the calculated source temperature and angular size. More direct support comes from the spectrum of $N\sim1000$ events recorded by the Kamiokande-II detector on the day of SN 1987A, which appear to show an 8 MeV line atop the detector background. This $\barν$ line, if genuine, has been well-hidden for 30 years because it occurs very close to the peak of the background. This fact might ordinarily justify extreme skepticism. In the present case, however, a more positive view is called for based on (a) the very high statistical significance of the result $(30 σ),$ (b) the use of a detector background independent of the SN 1987A data using a later K-II data set, and (c) the observation of an excess above the background spectrum whose central energy and width both agree with that of an 8 MeV $\barν$ line broadened by $25\%$ resolution. Lastly, it is noted that the tachyonic interpretation of the Mont Blanc burst fits the author's earlier unconventional $3+3$ model of the neutrino mass states.