Democratic Seesaw Mass Matrix Model

A seesaw mass matrix model is reviewed as a unification model of quark and lepton mass matrices. The model can understand why topquark mass mt is so singularly enhanced compared with other quark masses, especially, why mt ≫ mb in contrast to mu ∼ md, and why only top-quark mass is of the order of the electroweak scale ΛW , i.e., mt ∼ O(ΛW ). The model predicts the fourth up-quark t′ with a mass mt′ ∼ O(mWR), and an abnormal structure of the right-handed upquark mixing matrix U R. Possible new physics is discussed. Talk at the Workshop on Masses and Mixings of Quarks and Leptons, University of Shizuoka, March 19 – 21, 1997. To be appeared in the Proceedings, 1997. † E-mail: [email protected]