Saturating the bound on the scale of fermion mass generation

Recently, Jager and Willenbrock have shown that the Appelquist and Chanowitz bound on the scale of top-quark mass generation can formally be saturated at tree-level in a particular Limit of a two-Higgs doubler model. In this note I present an alternate derivation of their result. I perform a coupled channel analysis for f (f) over bar, VLVL and VLVL --> VLVL scattering and derive the conditions on the parameters required for f (f) over bar, VLVL scattering to be relevant to unitarity. I also show that it is not possible to saturate the bound on fermion mass generation in a two-Higgs model while maintaining tree-level unitarity in Higgs scattering at high energies. (C) 1998 Elsevier Science B.V. All rights reserved.