Does the three site Higgsless model survive the electroweak precision tests at loop?

TL;DR

This paper evaluates whether the three site Higgsless model remains consistent with electroweak precision tests at the one-loop level, focusing on the parameters S and T and their dependence on physical observables.

Contribution

It provides the complete one-loop renormalization group equations and matching conditions for the model, and analyzes the constraints from precision data on physical parameters.

Findings

Electroweak data severely constrains the model's parameters.

Perfect fermiophobity of W' is ruled out by precision tests.

Cutoff dependence of the analysis is minimal despite non-renormalizability.

Abstract

We complete the list of one loop renormalization group equations and matching conditions relevant for the computation of the electroweak precision parameters $S$ and $T$ in the three site Higgsless model. We obtain one-loop formulas for $S$ and $T$ expressed in terms of physical observables such as the KK gauge boson mass $M_{W'}$, the KK fermion mass $M$, and the KK gauge boson ($W'$) couplings with light quarks and leptons $g_{W'ff}$. It is shown that these physical observables, $M_{W'}$, $M$ and $g_{W'ff}$ are severely constrained by the electroweak precision data. Unlike the tree level analysis on the ideally delocalized fermion, we find that perfect fermiophobity of $W'$ is ruled out by the precision data. We also study the cutoff dependence of our analysis. Although the model is non-renormalizable, the dependence on the cutoff parameter $\Lambda$ is shown to be non-significant.