Flavor Symmetry and Vacuum Aligned Mass Textures

The mass matrix forms of quarks and leptons are studied in a theory with permutation flavor symmetry. The structure of the scalar potential is analyzed in the case that the electroweak doublet Higgs fields have non-trivial flavor symmetry charges. We find that realistic forms of the mass matrices are obtained dynamically in the vacuum of the theory, where some of the Higgs fields have vanishing expectation values which lead to vanishing elements in the quark and lepton mass matrices. Mass textures are realized in the true vacuum, and their positions are controlled by the flavor symmetry. An interesting point is that, due to the flavor group structure, the up and down quark mass matrices are automatically different in the vacuum. This leads to non-vanishing generation mixing. It is also discussed that it is necessary for the flavor symmetry to be broken to realize scalars whose masses are not too small. The lower bounds of the Higgs masses are derived from the experimental data of flavor-changing rare processes, such as neutral K meson mixing.