SN1987A and neutrino non-radiative decay

Abstract

We investigate neutrino non-radiative two-body decay in vacuum, in relation to SN1987A. In a full $3\nu$ decay framework, we perform a detailed likelihood analysis of the 24 neutrino events from SN1987A observed by Kamiokande-II, IMB, and Baksan. We consider both normal and inverted neutrino mass orderings, and the possibility of strongly hierarchical and quasi-degenerate neutrino mass patterns. The results of the likelihood analysis show that the sensitivity is too low to derive bounds in the case of normal mass ordering. On the contrary, in the case of inverted mass ordering we obtain the bound $\tau/m \ge 2.4 \times 10^{5}$ s/eV ($1.2 \times 10^{5}$) s/eV at 68 $\%$ (90 $\%$) CL on the lifetime-to-mass ratio of the mass eigenstates $\nu_2$ and $\nu_1$.