Telling three from four neutrinos at the neutrino factory Original Research Article

We upgrade the study of the physical reach of a neutrino factory considering the possibility to distinguish a three (active) neutrino oscillation scenario from the scenario in which a light sterile neutrino is also present. The distinction is easily performed in the so-called 2+2 scheme, but also in the more problematic 3+1 scheme it can be attained in some regions of the parameter space. We also discuss the CP violating phase determination, showing that the effects of a large phase in the three-neutrino theory cannot be reproduced in a four-neutrino, CP conserving, model.