Four-Neutrino Mass Spectra and the Super-Kamiokande Atmospheric Up-Down Asymmetry

Abstract

In the framework of schemes with mixing of four massive neutrinos, which can accommodate the atmospheric, solar and LSND ranges of Delta m^2, we show that, in the whole region of Delta m^2_{LSND} allowed by LSND, the Super-Kamiokande up-down asymmetry excludes all mass spectra with a group of three close neutrino masses separated from the fourth mass by the LSND gap of order 1 eV. Only two schemes with mass spectra in which two pairs of close masses are separated by the LSND gap can describe the Super-Kamiokande up-down asymmetry and all other existing neutrino oscillation data.

Figures (2)

• Figure 1: The six types of neutrino mass spectra that can accommodate the solar, atmospheric and LSND scales of $\Delta{m}^2$. The different distances between the masses on the vertical axes symbolize the different scales of $\Delta{m}^2$. The spectra (I) -- (IV) define class 1, whereas class 2 comprises (A) and (B).
• Figure :