The MiniBooNE anomaly and heavy neutrino decay

Abstract

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 (${\nu }_h$) in the MiniBooNE detector. The ${\nu }_h$ is created by mixing in ${\nu }_{\mu }$ neutral-current interactions and decays radiatively into $\nu \gamma$ due to a transition magnetic moment between the ${\nu }_h$ and a light neutrino $\nu$. The energy measured in the detector arises from the subsequent conversion of the decay photon into a $\text{pair}$ pair within the detector volume. The analysis of the energy and angular distributions of the excess events suggests that the ${\nu }_h$ has a mass around 500 MeV and the lifetime ${\tau }_{{\nu }_h}\lesssim 10^{-9}$ s. Existing experimental data are found to be consistent with a mixing strength between the ${\nu }_h$ and the ${\nu }_{\mu }$ of $|U_{\mu h}{|}^2\simeq (1-4)\times 10^{-3}$ and a ${\nu }_h$ transition magnetic moment of ${\mu }_{tr}\simeq (1-6)\times 10^{-9}{\mu }_B$. Finally, we discuss the reason why no significant excess of low energy events has been observed in the recent antineutrino data.

Comments: version accepted for publication in Phys. Rev. Lett