Short-baseline electron neutrino disappearance, tritium beta decay, and neutrinoless double-beta decay

We consider the interpretation of the MiniBooNE low-energy anomaly and the gallium radioactive source experiments anomaly in terms of short-baseline electron neutrino disappearance in the framework of $3+1$ four-neutrino mixing schemes. The separate fits of MiniBooNE and gallium data are highly compatible, with close best-fit values of the effective oscillation parameters Δm² and sin²2ϑ. The combined fit gives Δm²0.1 eV² and 0.11sin²2ϑ0.48 at 2σ. We consider also the data of the Bugey and Chooz reactor antineutrino oscillation experiments and the limits on the effective electron antineutrino mass in β decay obtained in the Mainz and Troitsk tritium experiments. The fit of the data of these experiments limits the value of sin²2ϑ below 0.10 at 2σ. Considering the tension between the neutrino MiniBooNE and gallium data and the antineutrino reactor and tritium data as a statistical fluctuation, we perform a combined fit which gives Δm²2 eV and 0.01sin²2ϑ0.13 at 2σ. Assuming a hierarchy of masses m₁, m₂, m₃m₄, the predicted contributions of m₄ to the effective neutrino masses in β decay and neutrinoless double-β decay are, respectively, between about 0.06 and 0.49 and between about 0.003 and 0.07 eV at 2σ. We also consider the possibility of reconciling the tension between the neutrino MiniBooNE and gallium data and the antineutrino reactor and tritium data with different mixings in the neutrino and antineutrino sectors. We find a 2.6σ indication of a mixing angle asymmetry.