Explaining the MiniBooNE excess by a decaying sterile neutrino with mass in the 250 MeV range
The MiniBooNE Collaboration has reported an excess of $460.5\ifmmode\pm\else\textpm\fi{}99.0$ electronlike events ($4.8\ensuremath{\sigma}$). 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 ${10}^{\ensuremath{-}11}\ensuremath{\lesssim}|{U}_{\ensuremath{\ell}4}{|}^{2}\ensuremath{\lesssim}{10}^{\ensuremath{-}7}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$). 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.