Explaining LSND by a decaying sterile neutrino

We propose an explanation of the LSND evidence for electron antineutrinoappearance based on neutrino decay. We introduce a heavy neutrino, which isproduced in pion and muon decays because of a small mixing with muon neutrinos,and then decays into a scalar particle and a light neutrino, predominantly ofthe electron type. We require values of $g m_4\sim$ few eV, $g$ being theneutrino--scalar coupling and $m_4$ the heavy neutrino mass, e.g. $m_4$ in therange from 1 keV to 1 MeV and $g \sim 10^{-6} - 10^{-3}$. Performing a fit tothe LSND data as well as all relevant null-result experiments, we show that alldata can be explained within this decay scenario. In the minimal version of thedecay model, we predict a signal in the upcoming MiniBooNE experimentcorresponding to a transition probability of the same order as seen in LSND. Inaddition, we show that extending our model to two nearly degenerate heavyneutrinos it is possible to introduce CP violation in the decay, which can leadto a suppression of the signal in MiniBooNE running in the neutrino mode. Webriefly discuss signals in future neutrino oscillation experiments, we showthat our scenario is compatible with bounds from laboratory experiments, and wecomment on implications in astrophysics and cosmology.Comment: 23 pages, 5 figures, minor improvements, matches published versio