Texture of a four-neutrino mass matrix

We propose a simple texture of the neutrino mass matrix with one sterile ne utrino along with the three standard ones. It gives maximal mixing angles f or nu(e) --> nu(S) and nu(mu) --> nu(tau) oscillations or vice versa. Thus with only four parameters, this mass matrix can explain the solar neutrino anomaly, atmospheric neutrino anomaly, LSND result and the hot dark matter of the universe, while satisfying all other Laboratory constraints. Dependi ng on the choice of parameters, one can get the vacuum oscillation or the l arge angle MSW solution of the solar neutrino anomaly. (C) 1998 Elsevier Sc ience B.V. All rights reserved.