A Majorana type of the neutrino mass matrix induces a class of lepton number violating processes. Cross sections of these reactions are given in terms of the neutrino mass matrix element, and a semi-realistic event rate is estimated. These processes provide mass and mixing parameters not directly accessible by the neutrino oscillation experiments. If these processes are discovered with a larger...

For the non-Hermitian Fritzsch-type mass matrix (M̃u, M̃d), which is a general expression of quark mass matrices, the rephasing-gauge dependency and δ-dependency (where Vub = |Vub|e) of each matrix element M̃qij (q = u, d; i, j = 1, 2, 3) are investigated. We find that the textures of (M̃u, M̃d) depend on the rephasing gauge and we can always take M̃u32 = 0 without losing generality, so that the rema...

An overview is given of the experimental neutrino mixing results and types of neutrino models proposed, with special attention to the general features of various GUT models involving intra-family symmetries and horizontal flavor symmetries. Many of the features are then illustrated by a specific SO(10) SUSY GUT model formulated by S.M. Barr and the author which can explain all four types of sol...