Heavy neutrino decays at MiniBooNE

TL;DR

This paper proposes a model involving a heavy sterile neutrino with specific decay properties to explain the MiniBooNE excess, consistent with other experimental constraints and suggesting implications for dark matter searches.

Contribution

It introduces a detailed sterile neutrino decay model that accounts for MiniBooNE data and predicts a second sterile neutrino affecting air showers and dark matter experiments.

Findings

Heavy neutrino with ~50 MeV mass can explain MiniBooNE excess.

Long lifetime and Dirac nature influence event energy and directionality.

Presence of a second sterile neutrino impacts air showers and dark matter detection.

Abstract

It has been proposed that a sterile neutrino \nu_h with m_h \approx 50 MeV and a dominant decay mode (\nu_h -> \nu\gamma) may be the origin of the experimental anomaly observed at LSND. We define a particular model that could also explain the MiniBooNE excess consistently with the data at other neutrino experiments (radiative muon capture at TRIUMF, T2K, or single photon at NOMAD). The key ingredients are (i) its long lifetime (\tau_h\approx 3-7x10^{-9} s), which introduces a 1/E dependence with the event energy, and (ii) its Dirac nature, which implies a photon preferably emitted opposite to the beam direction and further reduces the event energy at MiniBooNE. We show that these neutrinos are mostly produced through electromagnetic interactions with nuclei, and that T2K observations force BR(\nu_h -> \nu_\tau\gamma) \le 0.01 \approx BR(\nu_h -> \nu_\mu\gamma). The scenario implies then the presence of a second sterile neutrino \nu_{h'} which is lighter, longer lived and less mixed with the standard flavors than \nu_h. Since such particle would be copiously produced in air showers through (\nu_h -> \nu_{h'}\gamma) decays, we comment on the possible contamination that its photon-mediated elastic interactions with matter could introduce in dark matter experiments.