Vector-like Strong Coupling theory with small S and T parameters

Abstract

We propose a mechanism which can reduce the Peskin and Takeuchi's S, T and U parameters in dynamical electroweak symmetry breaking models. It is interesting that not only S but also T parameter can become small even if there exists large isospin violation in fermion condensation. For example, when we take the $SU(2)_L\times U(1)_Y$ breaking mass of up-type fermion $m_U=1$ TeV and that of down-type $m_D=0$, we get S$\sim 0.001 N$ and T$\sim 0.05 N$ for the $SU(2)_L\times U(1)_Y$ invariant masses $M=10$ TeV. The point is that these parameters are suppressed by $SU(2)_L\times U(1)_Y$ invariant masses which the vector-like fermions can have.