Explaining the MiniBooNE Excess Through a Mixed Model of Oscillation and Decay

The electron-like 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 data sets 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 ∆χ 2 /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.