The MiniBooNE anomaly and heavy neutrino decay

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The anomaly in the low energy distribution of quasi-elastic neutrino events reported by the MiniBooNE collaboration is discussed. We show that the observed excess of electron-like events could originate from the production and decay of a heavy neutrino (νₕ) in the MiniBooNE detector. The νₕ is created by mixing in νμ neutral-current interactions and decays radiatively into νγ due to a transition magnetic moment between the νₕ and a light neutrino ν. The energy measured in the detector arises from the subsequent conversion of the decay photon into a pair within the detector volume. The analysis of the energy and angular distributions of the excess events suggests that the νₕ has a mass around 500 MeV and the lifetime τνₕ 10⁻⁹ s. Existing experimental data are found to be consistent with a mixing strength between the νₕ and the νμ of |Uμₕ|² ≃ (1-4)× 10⁻³ and a νₕ transition magnetic moment of μtr ≃ (1- 6)× 10⁻⁹ μB. Finally, we discuss the reason why no significant excess of low energy events has been observed in the recent antineutrino data.