A STERILE NEUTRINO SCENARIO CONSTRAINED BY EXPERIMENTS AND COSMOLOGY

We analyze a scheme in which three active neutrinos and one sterile ne utrino account for the solar, the atmospheric and the LSND neutrino an omalies in a model-independent way. It is shown that if the equivalent number, N-nu, of the light neutrino species is less than 4, then the constraints from these anomalies, accelerator and reactor experiments and big bang nucleosynthesis force a general 4 x 4 mixing matrix to be effectively split into two 2 x 2 matrices. If these neutrinos are of the Majorana type, then negative results of neutrinoless double beta d ecay experiments imply that the total mass of neutrinos is not suffici ent to account for all the hot dark matter components.