Electroweak precision observables at one loop in Higgsless models

Abstract

We study the viability of generic Higgsless models at low energies when compliance with electroweak precision observables and unitarity constraints up to the TeV scale are imposed. Our analysis shows that consistency with $S$ and $T$ can be achieved at the one-loop level even with a single light vector state, ${m}_{V}\ensuremath{\lesssim}500\text{ }\text{ }\mathrm{GeV}$. However, this scenario turns out to be strongly disfavored when direct resonance searches at the Tevatron are also taken into account. We show that a fully consistent picture can be obtained if an axial state is introduced. Interestingly, ${m}_{V}$ is still predicted to be light (below 1 TeV) while typical values of ${m}_{A}$ span over the window $1.2{m}_{V}\ensuremath{\le}{m}_{A}\ensuremath{\le}1.4{m}_{V}$. Our results for the vector channel are rather robust and well within the reach of present-day colliders, while the axial channel is more loosely constrained.