Charged Lepton and Down-Type Quark Masses in SU (1, 1) Model and the Structure of Higgs Sector

The simplest noncompact group SU (1, 1), when introduced as a symmetry group of the generations of quarks and leptons in the framework of a vectorlike theory, gives an excellent viewpoint on low-energy physics. The minimal setup of the scheme, however, gives a phenomenologically unacceptable prediction on the Yukawa coupling matrices. This suggests that the higgs sector has a richer structure than we expect from the success of MSSM. A natural extension of the scheme, which has a double structure in the higgs sector, is formulated. The framework allows this extension in a restrictive way. The possible patterns of Yukawa couplings are classified and the expressions of the coupling matrices are presented.