Neutrino mass due to the mixing among neutrinos and gauginos
  We consider the explanation of both data of the atmospheric neutrino and the solar neutrino by the neutrino mass matrix derived from the mixing of neutrinos and gauginos in the extended MSSM with an extra U(1) gauge symmetry. This scenario directly relates the neutrino mass to supersymmetry. The structure of the mass hierarchy and the mixing is determined only by the extra U(1)-charge of neutrinos. Although the model is rather simple, it may be able to realize both the small and large mixing angle solutions for the solar neutrino problem. In particular, the large mixing angle MSW solution for the solar neutrino problem can be easily realized. We discuss the relation between the extra U(1)-charge and four solutions for the solar neutrino problem. 
Daijiro Suematsu