On The Decaying-Sterile Neutrino Solution to the Electron (Anti)Neutrino Appearance Anomalies

Abstract

We explore the hypothesis that the unexplained data from LSND and MiniBooNE are evidence for a new, heavy neutrino mass-eigenstate that mixes with the muon-type neutrino and decays into an electron-type neutrino and a new, very light scalar particle. We consider two different decay scenarios, one with Majorana neutrinos, one with Dirac neutrinos; both fit the data equally well. We find a reasonable, albeit not excellent, fit to the data of MiniBooNE and LSND. The decaying-sterile-neutrino hypothesis, however, cleanly evades constraints from disappearance searches and precision measurements of leptonic meson decays, as long as $1\mathrm{MeV}\gtrsim m_4\gtrsim 10$~keV. The SBN program at Fermilab should be able to definitively test the decaying-sterile-neutrino hypothesis.

Comments: This version v2 has been accepted for publication in JHEP. The changes from previous version are: inclusion of the data from KARMEN in the analysis, a new subsection about the sensitivity of SBN to nonzero decay effects, an new appendix describing the details of MiniBooNE analysis, additional references and some other minor changes