Holographic description of $SO(5) \rightarrow SO(4)$ composite Higgs model

TL;DR

This paper develops a 5D holographic model for the minimal composite Higgs scenario with $SO(5) o SO(4)$ symmetry breaking, predicting a spectrum of resonances consistent with experimental constraints and extending previous QCD-inspired approaches.

Contribution

It introduces a novel 5D holographic framework for the $SO(5) o SO(4)$ composite Higgs model, including detailed resonance spectra and phenomenological analysis.

Findings

Resonances with masses between 1 and 2 TeV are compatible with experimental data.

Degeneracy between vector and scalar Regge trajectories for unbroken $SO(4)$ states.

Goldstone bosons correspond to the four lightest massless resonances.

Abstract

We study a 5D bottom-up holographic model that is expected to describe the dynamics of the minimal composite Higgs model characterized by a $SO(5)\to SO(4)$ global symmetry breaking pattern. We assume that the fundamental degrees of freedom are scalars transforming under some representation of $SO(5)$ and subject to some unspecified strong interactions. The holographic description presented here is inspired by previous studies performed in the context of QCD and it allows for the consideration of spin one and spin zero resonances. The resulting spectrum leads in a natural way to a variety of resonances. Namely, those transforming under the unbroken $SO(4)$ subgroup exhibit an exact degeneracy between the two Regge trajectories of vector and scalar channels, while the resonances with quantum numbers in the $SO(5)/ SO(4)$ coset lie on a trajectory of (heavier) spin one states and a non-degenerated one of scalar resonances where the four lowest lying ones are massless. These correspond to the four Goldstone bosons in 4D associated to the global symmetry breaking pattern. Restrictions derived from the experimental constraints (Higgs couplings, $S$ parameter, etc.) are then implemented and we conclude that the model is able to accommodate vector and scalar resonances with masses in the range 1 TeV to 2 TeV without encountering phenomenological difficulties. Extension to generic models characterized by the breaking pattern $SO(N)\to SO(N^\prime<N)$ is straightforward.