Neutrino oscillations and the supernova 1987A signal

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 νₑ with ν_μ or ν_τ with those mixing parameters that would solve the solar neutrino problem. For the small-angle MSW solution (Δm²≈10^-5 eV², sin²2Θ₀≈0.007), 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 νₑ temperature. There is only marginal overlap between the upper end of the 95.4% C.L. inferred range of 〈E_νₑ〉 and the lower end of the range of theoretical predictions. Any admixture of the stiffer ν_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 (Δm²≈10^-5 eV², sin²2Θ₀≈0.7) 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 νₑ spectra. For the solar vacuum solution (Δm²≈10^-10 eV², sin²2Θ₀≈1) the oscillations in the SN are nonadiabatic; vacuum oscillations take place between the SN and the detector. If one of the two large-angle solutions were borne out by the upcoming round of solar neutrino experiments, one would have to conclude that the SN 1987 A ν_μ and/or νₑ spectra had been much softer than predicted by current treatments of neutrino transport.