Iranian Journal of Physics Research

Composite Higgs Model Involving a Light Scalar Sigma and the study of Phenomenological Constraints

Articles in Press

Document Type : Original Article

Authors

K Bitaghsir Fadafan 1
Reza Asgharzadeh 2
Moslem Ahmadvand 2

1 Faculty of Physics, Shahrood University of Technology, Shahrood, Iran

2 Physics Faculty, Shahrood University of Technology, P.O.Box 3619995161 Shahrood, Iran

Abstract
In this research, we consider Composite Higgs Models with a relatively small global symmetry-breaking scale,
f in the strong coupling sector, where the Higgs boson emerges as a pseudo-Nambu-Goldstone boson. The model also includes a singlet scalar resonance, the sigma particle (σ), which mixes with the Higgs. Using an effective chiral Lagrangian, the structure of the theory's vacuum minima is analyzed. It is shown that in the absence of σ, achieving f scales above 1 TeV requires a small amount of fine-tuning to be consistent with experimental constraints. However, mixing with this light scalar particle resolves this tension and allows for a lower f scale. Subsequently, we impose up-to-date experimental constraints based on combined LHC Run-2 fits on the Higgs couplings to gauge bosons and the top quark. By also applying limits from Higgs exotic decay searches, the model's parameter space is quantitatively determined, and viable benchmark points are extracted. Furthermore, an alternative scenario based on the CDF results is investigated to illustrate the model's sensitivity to independent collider data. The analyses demonstrate that the presence of the light scalar σ can effectively alleviate constraints arising from the electroweak precision parameters S
and T as well as deviations in the Higgs couplings.

Keywords

Composite Higgs
- Beyond Standard Model - Electroweak Theory - Symmetry Breaking
Subjects
Iranian Journal of Physics Research

Articles in Press, Accepted Manuscript
Available Online from 20 July 2026

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