Neutrino Oscillations and the Supernova 1987A Signal

Abstract

We study the impact of neutrino oscillations on the interpretation of the supernova (SN) 1987A neutrino signal by means of a maximum-likelihood analysis. We focus on oscillations between $\overlineν_e$ with $\overlineν_μ$ or $\overlineν_τ$ with those mixing parameters that would solve the solar neutrino problem. For the small-angle MSW solution ($Δm^2\approx10^{-5}\,\rm eV^2$, $\sin^22Θ_0\approx0.007$), there are no significant oscillation effects on the Kelvin-Helmholtz cooling signal; we confirm previous best-fit values for the neutron-star binding energy and average spectral $\overlineν_e$ temperature. There is only marginal overlap between the upper end of the 95.4\% CL inferred range of $\langle E_{\overlineν_e}\rangle$ and the lower end of the range of theoretical predictions. Any admixture of the stiffer $\overlineν_μ$ spectrum by oscillations aggravates the conflict between experimentally inferred and theoretically predicted spectral properties. For mixing parameters in the neighborhood of the large-angle MSW solution ($Δm^2\approx10^{-5}\,\rm eV^2$, $\sin^22Θ_0\approx0.7$) the oscillations in the SN are adiabatic, but one needs to include the regeneration effect in the Earth which causes the Kamiokande and IMB detectors to observe different $\overlineν_e$ spectra. For the solar vacuum solution ($Δm^2\approx10^{-10}\,\rm eV^2$, $\sin^22Θ_0\approx1$) the oscillations in the SN are nonadiabatic; vacuum oscillations take place between the SN and the detector. If either of the large-angle solutions were borne out by the upcoming round of solar neutrino experiments, one would have to conclude that the SN~1987A $\overlineν_μ$ and/or $\overlineν_e$ spectra had been much softer than predicted by current

Final version with very minor wording changes, to be published in Phys. Rev. D