Seesaw-Type Quark and Lepton Mass Matrices and U(3)-Family Nonet Higgs Bosons

A unified mass matrix model of quarks and leptons with a seesaw-type form $M_f=m M_F^{-1} m$ is proposed on the basis of a non-standard Higgs scenario. The matrix $m$ is provided by U(3)-family nonet bosons $\phi$, and the matrix $M_F$ is a mass matrix of heavy fermions $F_i$ corresponding to the ordinary fermions $f_i=\nu_i,e_i,u_i,d_i$ ($i=1,2,3$). It is shown that a Higgs potential of $\phi$ with a broken U(3)-family symmetry leads to a desirable charged lepton mass formula when $M_E\propto {\bf 1}$. Then, phenomenologically desirable forms of heavy quark mass matrices $M_Q$ ($Q=U,D$) are investigated.