S and T Parameters in the Fermion Condensate Model

TL;DR

This paper calculates the S and T electroweak parameters in a composite Higgs model with added vector-like fermions, showing how these parameters constrain the model and can accommodate a heavy Higgs boson.

Contribution

It introduces a composite Higgs model with vector-like fermions and analyzes electroweak corrections, providing new constraints and insights into Higgs mass compatibility.

Findings

T parameter constrains the mixing angle of new fermions.

S parameter does not constrain the fermion masses.

Model allows for a heavy Higgs consistent with electroweak data.

Abstract

We calculate the oblique electroweak corrections and confront them with the experiments in a composite Higgs version of the standard model. A vector-like weak doublet and a singlet fermion are added to the standard model without elementary Higgs. Due to quartic coupling there is a mixing between the components of the new fields triggering electroweak symmetry breaking. The Peskin-Takeuchi S and T electroweak parameters are presented. The new sector of vector-like fermions is slightly constrained, T gives an upper bound on the mixing angle of the new fermions, which is already constrained by self-consistent gap-equations. S gives no constraints on the masses. This extension can give a positive contribution to T, allowing for a heavy Higgs boson in electroweak precision tests of the Standard Model.