UV Completions of Partial Compositeness: The Case for a SU(4) Gauge Group

TL;DR

This paper introduces a UV-complete model based on an SU(4) gauge theory with fermionic matter, providing a viable partial compositeness framework that naturally incorporates custodial symmetry and top partners, avoiding problematic Landau poles.

Contribution

It presents a novel SU(4) gauge theory model for partial compositeness with a specific matter content, symmetry breaking pattern, and phenomenological features, advancing composite Higgs model building.

Findings

The IR theory is based on the SU(5)/SO(5) coset with specific top partners.

The model naturally incorporates custodial symmetry and avoids Landau poles.

The top and bottom quark masses are computed, with minimal deviations from SM predictions.

Abstract

We present a model of partial compositeness arising as the IR limit of a SU(4) gauge theory with only fermionic matter. This group is one of the most promising ones among a handful of possible choices allowing a symmetry breaking pattern incorporating custodial symmetry and a top partner candidate, while retaining asymptotic freedom. It is favored for not giving rise to lepto-quarks or Landau poles in the SM gauge couplings. The minimal UV theory consists of five hyperfermions in the anti-symmetric representation and three in the fundamental and anti-fundamental. The IR theory is centered around the coset SU(5)/SO(5), with top partners in the fundamental of SO(5), giving rise to one composite fermion of electric charge 5/3, three of charge 2/3 and one of charge -1/3. Electro-Weak symmetry breaking occurs via top-quark-driven vacuum misalignment. The top quark mass is generated via the mechanism of partial compositeness, while the remaining fermions acquire a mass via a standard quadratic coupling to the Higgs. We compute the top and bottom quark mass matrix and the Electro-Weak currents of the composite fermions. The model does not give rise to unacceptably large deviations from the SM Z\to b \bar b decay width.