Three families from SU(4)[Formula presented]⊗SU(3)[Formula presented]⊗SU(2)[Formula presented]⊗U(1)[Formula presented] SM-like chiral models

We give a detailed description of the model construction procedures about our new approach to the family structure of the standard model. SM-like chiral fermion spectra, largely “derivable” from the gauge anomaly constraints, are formulated in an [Formula presented] symmetry framework as an extension of the SM symmetry. The [Formula presented] case gives naturally three families as a result, with U[Formula presented] nontrivially embedded into the [Formula presented] Such a spectrum has extra vectorlike quarks and leptons. We illustrate how an acceptable symmetry-breaking pattern can be obtained through a relatively simple scalar sector which gives naturally hierarchical quark mass matrices. Compatibility with various FCNC constraints and some interesting aspects of the possible phenomenological features are discussed, from a non-model-specific perspective. The question of incorporating supersymmetry without putting in the Higgs bosons as extra supermultiplets is also addressed.