Heavy neutrino decays at MiniBooNE

It has been proposed that a sterile neutrino v(h), with m(h) approximate to 50 MeV and a dominant decay mode v(h) -> v 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.TRIUME, 12K, or single photon at NOMAD). The key ingredients are (i) its long lifetime (T-h approximate to 3-7 x 10(-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 13R(v(h) -> v(T) gamma) <= 0.01 approximate to BR(v(h ->) v(mu)gamma). The scenario implies then the presence of a second sterile neutrino v(h)' which is lighter, longer lived and less mixed with the standard flavors than v(h). Since such particle would be copiously produced in air showers through v(h) -> vh' gamma decays, we comment on the possible contamination that its photon-mediated elastic interactions with matter could introduce in dark matter experiments.