Sterile neutrinos: a revived assumption?

The American experiment MiniBooNE may confirm results obtained in the ninety years about the existence of a 4. type of neutrinos. Since 2002, the MiniBooNE experiment, installed near the Fermilab, has been studying the transformation of muon neutrinos into electron neutrinos. 380 electron neutrinos in excess of what was expected by the standard model of particle physics have been detected by MiniBooNE. A possible explanation could be the existence of a 4. type of neutrinos that should interact with matter very, very little. Other experiments performed near nuclear reactors show anomalies that could be interpreted as the effect of sterile neutrinos. The question stays open as the measurement is difficult and other explanations are likely such as a more or less accurate assessment of the background noise. (A.C.)