MiniBooNE anomaly and heavy neutrino decay.

The anomaly in the low-energy distribution of quasielastic neutrino events reported by the MiniBooNE Collaboration is discussed. We show that the observed excess of electronlike events could originate from the production and decay of a heavy neutrino (nu(h)) in the MiniBooNE detector. The nu(h) with the mass around 500 MeV is created by mixing in nu(mu) neutral-current interactions and decays radiatively into nu gamma with the lifetime tau(nu(h)) approximately < 10(-9) s due to a transition magnetic moment between the nu(h) and a light neutrino nu. Existing experimental data are found to be consistent with a mixing strength between the nu(h) and the nu_{mu} of |U(mu h)|2 approximately = (1-4)x10(-3) and a nu(h) transition magnetic moment of mu(tr) approximately (1-6)x10(-9) mu(B). Finally, we discuss the reason why no significant excess of low-energy events has been observed in the recent antineutrino data.