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 (νₕ) in the MiniBooNE detector. The νₕ with the mass around 500 MeV is created by mixing in ν_μ neutral-current interactions and decays radiatively into νγ with the lifetime τ_νₕ10^-9 s due to a transition magnetic moment between the νₕ and a light neutrino ν. Existing experimental data are found to be consistent with a mixing strength between the νₕ and the ν_μ of |U_μh|²(1-4)×10^-3 and a νₕ transition magnetic moment of μₜᵣ(1-6)×10^-9μB. Finally, we discuss the reason why no significant excess of low-energy events has been observed in the recent antineutrino data.