Explaining the MiniBooNE excess through a mixed model of neutrino oscillation and decay

The electronlike excess observed by the MiniBooNE experiment is explained with a model comprising a new low mass state (O(1) eV) participating in neutrino oscillations and a new high mass state (O(100) MeV) that decays to ν+γ. Short-baseline oscillation datasets are used to predict the oscillation parameters. Fitting the MiniBooNE energy and scattering angle data, there is a narrow joint allowed region for the decay contribution at 95% CL. The result is a substantial improvement over the single sterile neutrino oscillation model, with Δχ²/dof=19.3/2 for a decay coupling of 2.8×10^-7 GeV^-1, high mass state of 376 MeV, oscillation mixing angle of 7×10^-4 and mass splitting of 1.3 eV². This model predicts that no clear oscillation signature will be observed in the FNAL short baseline program due to the low signal-level.