Realistic Composite Higgs Models

TL;DR

This paper investigates how fermionic resonances in composite Higgs models affect electroweak precision tests, showing that models with multiple resonances can be compatible with constraints and potentially observable at the LHC.

Contribution

It provides a detailed one-loop analysis of electroweak constraints on fermionic resonances in SO(5)/SO(4) composite Higgs models, including arbitrary fermion couplings.

Findings

Minimal models struggle with electroweak constraints.

Models with multiple fermionic resonances are viable.

Fermionic resonances could be detected at the LHC.

Abstract

We study the role of fermionic resonances in realistic composite Higgs models. We consider the low energy effective description of a model in which the Higgs arises as the pseudo-Goldstone boson of an SO(5)/SO(4) global symmetry breaking pattern. Assuming that only fermionic resonances are present below the cut-off of our effective theory, we perform a detailed analysis of the electroweak constraints on such a model. This includes the exact one-loop calculation of the T parameter and the anomalous Zbb coupling for arbitrary new fermions and couplings. Other relevant observables, like b to s gamma and Delta B=2 processes have also been examined. We find that, while minimal models are difficult to make compatible with electroweak precision tests, models with several fermionic resonances, such as the ones that appear in the spectrum of viable composite Higgs models from warped extra dimensions, are fully realistic in a large region of parameter space. These fermionic resonances could be the first observable signature of the model at the LHC.