The original ν̄μ-(orν̄τ-) energy spectrum from the gravitational collapse of a star has a larger average energy than the spectrum for ν̄e since the opacity of ν̄e exceeds that of ν̄μ(orντ). Flavor neutrino conversion ν̄eν̄ μ induced by lepton mixing results in partial permutation of the original ν̄e and ν̄μ spectra. An upper bound on the permutation factor p≤0.35 (99% C.L.) is derived using the data from SN 1987A and a range of models of the neutrino emission. The relation between the permutation factor and the vacuum mixing angle is established, which leads to the upper bound on this angle. The upper bound sin22θ>0.7-0.9 excludes the large mixing angle solutions of the solar neutrino problem: "just-so" and, partly, MSW, as well as part of the region of the νe-νμ oscillation space which could be responsible for the atmospheric muon neutrino deficit. These limits are sensitive to the predicted neutrino spectrum and can be strengthened as supernova models improve.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)