Abstract
We explore the hypothesis that the unexplained data from Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments 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 MeV ≳ m4 ≳ 10 keV. The Short-Baseline Neutrino Program (SBN) at Fermilab should be able to definitively test the decaying-sterile-neutrino hypothesis.
Highlights
Under the assumption that there are no unaccounted for “mundane” explanations to these two excesses — unidentified background processes, problems with modelling the neutrino scattering process, detector-related effects, etc — these so-called short-baseline anomalies1 translate into new more physics — on top of nonzero active neutrino masses — in the neutrino sector
We explore the hypothesis that the unexplained data from Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments 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
Instead of assuming that a fourth eV-scale neutrino is produced coherently during pion or muon decay, we postulate that a heavier fourth neutrino mass eigenstate is produced in the neutrino source and that this new neutrino state decays into an electron-type neutrino and a new, effectively massless scalar particle [9]
Summary
We postulate the existence of a fourth neutrino mass eigenstate. Since we want to explain the data from LSND and MiniBooNE, the fourth neutrino must have a nonzero νμ component. It is easy to express eq (2.2) in a way that explicitly preserves the SU(2) × U(1) gauge symmetry of the standard model: in the limit Uμ4 1, ν4νeφ → νs(LeH)φ/Λ, where νs is the left-handed sterile neutrino field and Λ is the effective scale of the physics that leads to the decay Lagrangian.. The total decay rate of ν4 in the laboratory reference frame is given by eq (2.5) with gD → gM and an overall factor of 2 [25], accounting for the fact that there are two different allowed decay modes: It is straight-forward to compute, for a neutrino produced in a charged-current process involving muons, the energy and flavor of the neutrinos that reach the detector.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
