An effective Higgsless theory: Satisfying electroweak constraints and a heavy top quark

Abstract

The main challenge faced by Higgsless models of electroweak symmetry breaking is to reconcile the experimental constraints imposed by the precision electroweak data and the top quark phenomenology with the unitarity constraints imposed by longitudinal gauge boson scattering amplitudes. In this paper we expand on previous work, giving details of how delocalized fermions can be used to adjust the $S$ parameter to zero, while keeping the $T$ and $U$ parameters naturally suppressed. We also show that it is possible to obtain the top quark mass, without affecting the delay of unitarity violation of the $W^+ W^-\to W^+W^-$ scattering amplitude, by separating the mass scales of the fermion sector ($1/R_f$) from that of the gauge sector ($1/R_g$). The fermion sector scale $1/R_f$ is only weakly constrained by unitarity of the $t\bar{t}\to W^+ W^-$ scattering amplitude; thus the ratio $R_g/R_f$ can be quite large, and the top mass can be easily achieved. Anomalous right-handed couplings involving the third generation quarks also avoid constraints from experimental data if $1/R_f$ is sufficiently large.