Neutrino Mass Hierarchy and Stepwise Spectral Swapping of Supernova Neutrino Flavors

摘要

We examine a phenomenon recently predicted by numerical simulations of supernova neutrino flavor evolution: the swapping of supernova v_e and v_(μ,τ) energy spectra below (above) energy E_c for the normal (inverted) neutrino mass hierarchy. We present the results of large-scale numerical calculations which show that in the normal neutrino mass hierarchy case, E_c decreases as the assumed effective 2 × 2 vacuum ν_e≒ ν_(μ,τ) mixing angle (approx=θ_(13)) is decreased. In contrast, these calculations indicate that E_c is essentially independent of the vacuum mixing angle in the inverted neutrino mass hierarchy case. With a good neutrino signal from a future galactic supernova, the above results could be used to determine the neutrino mass hierarchy even if θ_(13) is too small to be measured by terrestrial neutrino oscillation experiments.