Can a mass inversion save solar neutrino oscillations from the LSND neutrino?

Abstract

In the light of the ν μ → ν e neutrino oscillations which may have been observed at the LSND experiment we explore the consequences of two inverted mass schemes where solar neutrino oscillations occur between ν e and ν τ . One favored LSND value, Δm 2 = 6 eV 2, leads to m ν e ≈ m ν τ ≈ 2.5 eV and m ν μ ≈ 0 so that cosmology can benefit from a recently proposed “cold plus hot dark matter” structure formation scenario with scenario with two equal mass light neutrinos (C ν 2DM). Solar neutrino oscillations ( ν e → ν τ ) can occur with one of the large mixing angle solutions so that a serious conflict with ββ decay Majorana mass limits is avoided without invoking Dirac masses. However, there is a problem with the SN 1987A signal because of resonant ν e ↔ ν μ oscillations which are expected to cause far higher ν e energies at the IMB and Kamiokande II detectors than have been observed. A small value Δm 2 ≈ 0.5 eV 2 at LSND, which allows for a relatively large ν e − ν μ mixing angle without conflicting with the KARMEN and BNL-E776 experiments, would indicate m ν e ≈ m ν τ ≈ 1.6eV and m ν μ ≈ 1.8eV. This scheme of C ν 3DM maintains, and even may improve, the essential cosmological model implications for large-scale structure, leaving no conflict with SN r-process nucleosynthesis.