Interaction of the SN1987A Neutrino with the Galaxy

In previous publications we have shown that long-ignored approximations in standard model calculations could have significant implications for very low mass particles such as neutrinos and photons. In particular we showed that, in a dilute plasma such as that in the solar corona, a significant decay probability of $\nu' \rightarrow \nu + \gamma$ will be possible as a consequence of the terms ignored in making the approximations. Here the $\nu'$ and $\nu$ are high and low mass eigenstates of the neutrino. In this paper, we investigate the effect in the vicinity of an expanding supernovae remnant such as SN1987A. We show that, in the dilute plasma external to the remnant, such decays are possible and significant. We describe a calculation of effects of such decays on the anti-neutrinos from SN1987A. The calculated anti-neutrino energy against arrival time agrees reasonably well with that observed, assuming that the expansion velocity of the remnant is $\approx 0.2 c$ and that the plasma density is high within the expanding remnant.