New physics in the third family and its effect on low-energy data

We investigate, in detail, a model in which the third family fermions are subjected to an SU(2) dynamics different from the first two families. Constrained by the precision Z-pole data, the heavy gauge boson mass is bounded from below to be about 1.7 TeV at the (Formula presented) level. The flavor-changing neutral current (FCNC) in the lepton sector can be significant in (Formula presented) and (Formula presented) transitions. In the latter case, the ratio (Formula presented) and (Formula presented) can constrain the model better than CERN LEP or SLC data in some region of the parameter space. Furthermore, FCNC’s are unavoidable in the quark sector. Significant effects to the (Formula presented) and (Formula presented) mixing and the rare decays of the K and B mesons, such as (Formula presented) (Formula presented) (Formula presented) (Formula presented) and (Formula presented) are expected.