Oscillations of three neutrinos with all Delta m^2 approx 10^{-3} eV^2

Abstract

Oscillations of three neutrinos with all squared mass splittings around 10^{-3} eV^2 are not firmly excluded by solar neutrino experiments. We carefully verify that they are also perfectly compatible with atmospheric neutrino experiments: due to accidental reasons the SuperKamiokande experiment is rather insensitive to `solar' nu_e/ν_mu oscillations, even if some characteristic small effects could become visible with more statistics. This pattern of oscillations can be excluded by new solar experiments, or cleanly discovered at KamLand. We also perform a fit of the most recent atmospheric SK data within the usual assumption that `solar' effects are negligible.