The Top Mass Upper Bound and Electroweak Radiative Corrections

Abstract

We investigated the possibility of introducing sizeable negative corrections to the $\varepsilon_{N1}$ ($\delta \rho$) parameter without affecting $\varepsilon_{N3}$. We have found that a proper vector-like family of fermions can imply such corrections. Differently from supersymmetry \cite{bcf}, this can be realized without introducing light particles easily observable at LEP II. Our example can be of particular interest if no new particle is found at LEP II and the $\varepsilon_{N1}$ value is found to be small compared to the one expected in the case of a large top mass.