NEUTRINO OSCILLATIONS AND THE SUPERNOVA 1987A SIGNAL

nWe study the impact of neutrino oscillations on the interpretation of the supernova (SN) 1987A neutrino signal by means of a maximum-likeli hood analysis. We focus on oscillations between <(nu)over bar (e)> wit h <(nu)over bar (mu)> or <(nu)over bar (tau)> with those mixing parame ters that would solve the solar neutrino problem. For the small-angle MSW solution (Delta m(2) approximate to 10(-5) eV(2), sin(2)2 Theta(0) approximate to 0.007), there are no significant oscillation effects o n the Kelvin-Helmholtz cooling signal; we confirm previous best-fit va lues for the neutron-star binding energy and average spectral <(nu)ove r bar (e)> temperature. There is only marginal overlap between the upp er end of the 95.4% C.L. inferred range of [<E (nu)over bar (e)>] and the lower end of the range of theoretical predictions. Any admixture o f the stiffer <(nu) over bar (mu)> spectrum by oscillations aggravates the conflict between experimentally inferred and theoretically predic ted spectral properties. For mixing parameters in the neighborhood of the large-angle MSW solution (Delta m(2) approximate to 10(-5) eV(2), sin(2)2 theta(0) approximate to 0.7) the oscillations in the SN are ad iabatic, but one needs to include the regeneration effect in the Earth which causes the Kamiokande and IMB detectors to observe different <( nu)over bar (e)> spectra. For the solar vacuum solution (Delta m(2) ap proximate to 10(-10) eV(2), sin(2)2 theta(0) approximate to 1) the osc illations in the SN are nonadiabatic; vacuum oscillations take place b etween the SN and the detector. If one of the two large-angle solution s were borne out by the upcoming round of solar neutrino experiments, one would have to conclude that the SN 1987A <(nu)over bar (mu)> and/o r <(nu)over bar (e)> spectra had been much softer than predicted by cu rrent treatments of neutrino transport.