Explaining the MiniBooNE excess by a decaying sterile neutrino with mass in the 250 MeV range

The MiniBooNE Collaboration has reported an excess of 460.5±99.0 electronlike events (4.8σ). We propose an explanation of these events in terms of a sterile neutrino decaying into a photon and a light neutrino. The sterile neutrino has a mass around 250 MeV, and it is produced from kaon decays in the proton beam target via mixing with the muon or the electron in the range 10^-11|U_4|²10^-7 (=e, μ). The model can be tested by considering the time distribution of the events in MiniBooNE and by looking for single-photon events in running or upcoming neutrino experiments, in particular by the suite of liquid argon detectors in the short-baseline neutrino program at Fermilab.