Low Energy Data and a Model of Flavor Mixing

Abstract

We consider a model in which the third family fermions are subjected to an SU(2) interaction different from the first two family fermions. Constrained by the Z-pole data, the heavy gauge boson mass is bounded from below to be about 1.7 TeV at the $2σ$ level. In this model, the flavor mixing between $τ$ and $μ$ can be so large that $Br(τ\to μ\bar{ν_μ} ν_τ)/ Br(τ\to e \bar{ν_e} ν_τ)$ and $Br(τ\to μμμ)$ provide a better constraint than the LEP/SLC data in some region of parameter space. Furthermore, flavor-changing neutral currents are unavoidable in the quark sector of the model. Significant effects to the $B^0-\bar{B^0}$ mixing and the rare decays of the $K$ and $B$ mesons, such as $K^\pm \to π^\pm ν{\bar ν}, b \to s ν{\bar ν}, B_s \to τ^+τ^-, μ^+μ^-$ and $B_{s,d} \to μ^\pm τ^\mp$, are expected.