Phenomenology of Sterile Neutrinos

Abstract

The indications in favor of short-baseline neutrino oscillations, which require the existence of one or more sterile neutrinos, are reviewed. In the framework of 3+1 neutrino mixing, which is the simplest extension of the standard three-neutrino mixing which can partially explain the data, there is a strong tension in the interpretation of the data, mainly due to an incompatibility of the results of appearance and disappearance experiments. In the framework of 3+2 neutrino mixing, CP violation in short-baseline experiments can explain the difference between MiniBooNE neutrino and antineutrino data, but the tension between the data of appearance and disappearance experiments persists because the short-baseline disappearance of electron antineutrinos and muon neutrinos compatible with the LSND and MiniBooNE antineutrino appearance signal has not been observed.