Light sterile neutrinos in particle physics: Experimental status

Most of the neutrino oscillation results can be explained by the three-neutrino paradigm. However several anomalies in short baseline oscillation data, corresponding to an L/E of about 1 m/MeV, could be interpreted by invoking a hypothetical fourth neutrino. This new state would be separated from the three standard neutrinos by a squared mass difference Delta m(new)(2) similar to 0.1-1 eV(2) and would have mixing angles of sin(2) 2 theta(ee) greater than or similar to 0.01 and sin(2) 2 theta(mu e) greater than or similar to 0.001, in the electron disappearance and appearance channels, respectively. This new neutrino, often called sterile, would not feel standard model interactions but mix with the others. Such a scenario calling for new physics beyond the standard model has to be either ruled out or confirmed with new data. After a brief review of the anomalous oscillation results we discuss the forthcoming laboratory experiments aiming to clarify the situation. (C) 2014 Published by Elsevier B.V.