Neutrino masses and mixing from neutrino oscillation experiments

Abstract

We discuss which information on neutrino masses and mixing can be obtained from the results of all neutrino oscillation experiments in the cases of three and four massive neutrinos. We show that in the three-neutrino case the neutrino oscillation data are not compatible with a hierarchy of couplings. In the case of four neutrinos, a hierarchy of masses is disfavored by the data and only two schemes with two pairs of neutrinos with close masses separated by a gap of the order of 1 eV can accommodate the results of all experiments.