Dynamical fermion mass generation by strong gauge interaction shielded by a scalar field.

Abstract

The strongly coupled lattice gauge models with confined fermion and scalar matter fields, which in a certain phase break dynamically a global chiral symmetry, are reconsidered from the point of view of the existence of heavy fermions. In these models heavy fermions can arise as neutral bound states of the fundamental fermion and scalar. We call this mechanism of dynamical fermion mass generation the shielded gauge mechanism. The scalar field induces at strong gauge coupling a second order phase transition which is necessary for a continuum limit. Therefore the mechanism might well exist also in continuum. In this case, assuming that strongly coupled chiral gauge theories with scalars have similar dynamical properties at strong coupling as the vectorlike models investigated on the lattice, the discussed mechanism could be considered as an alternative to the Higgs mechanism. In particular, if the broken global chiral symmetry is SU(2) and the heavy fermion interpreted as a top quark, the mechanism is analogous to some gauge models for the top quark condensate. We present some numerical data obtained in the quenched approximation of a model with vectorlike U(1) gauge symmetry. The observed scaling behavior of the chiral condensate and of the fermion mass and also the properties of Goldstone bosons are the first encouraging steps in a study of the continuum limit of the mechanism.