A 125 GeV composite Higgs boson versus flavour and electroweak precision tests

TL;DR

This paper examines the constraints on composite Higgs models with a 125 GeV mass from flavour and electroweak precision tests, identifying models with testable top partner masses around a TeV.

Contribution

It compares different fermion representations and flavour symmetries, highlighting models compatible with a light Higgs and accessible top partner masses.

Findings

Some models can accommodate a 125 GeV Higgs with top partners near 1 TeV.

Certain flavour symmetries reduce constraints, making discovery at LHC feasible.

Models with specific fermion representations are more consistent with precision tests.

Abstract

A composite Higgs boson of 125 GeV mass, only mildly fine-tuned, requires top partners with a semi-perturbative coupling and a mass not greater than about a TeV. We analyze the strong constraints on such picture arising from flavour and electroweak precision tests in models of partial compositeness. We consider different representations for the composite fermions and compare the case of an anarchic flavour structure to models with a U(3)^3 and U(2)^3 flavour symmetry. Although non trivially, some models emerge that look capable of accommodating a 125 GeV Higgs boson with top partners in an interesting mass range for discovery at the LHC as well as associated flavour signals.