On the dynamical symmetry breaking of the electroweak interactions by the top quark

We discuss the electroweak gauge symmetry breaking triggered by a new stron g attractive interaction to condensate fermion-antifermion, and topcolor is a prototype. To deal with the fermion pairing, a general method based on t he Hubbard-Stratonovich transformation in the functional integral approach is used. We derive a formula which relates the W +/-, Z(0) weak boson masses to that of the condensated fermion, thus generalizing the Pagels-Stokar formula ob tained in QCD. The custodial SU(2) electroweak symmetry turns out to be sys tematically violated, the deviation of rho = M-W(2)/(M(Z)(2)cos(2)theta(W)) from unity is related to the new physics scale Lambda. Some phenomenologic al consequences of the top-pair condensation models are discussed. Distinct ive signatures of the (t) over bar t scalar bound state, a Higgs boson like denoted by H-t, are the dominant decay modes H-t --> Y + gamma, H-t --> Y + Z(0), and H-t --> B* + (B) over bar*. (C) 2000 Elsevier Science B.V. All rights reserved.