The minimal linear sigma model for the Goldstone Higgs

TL;DR

This paper develops a complete, renormalizable linear sigma model incorporating the Higgs and a singlet scalar, analyzing its phenomenology and effective field theory limits relevant for electroweak symmetry breaking.

Contribution

It provides a comprehensive renormalizable Lagrangian for the minimal SO(5) linear sigma model including gauge and fermion sectors, and explores phenomenological implications.

Findings

Constraints from precision observables and LHC data are analyzed.

The effective d <= 6 Lagrangian is derived in the heavy fermion limit.

The model interpolates between perturbative and strongly coupled regimes.

Abstract

In the context of the minimal SO(5) linear {\sigma}-model, a complete renormalizable Lagrangian -including gauge bosons and fermions- is considered, with the symmetry softly broken to SO(4). The scalar sector describes both the electroweak Higgs doublet and the singlet {\sigma}. Varying the {\sigma} mass would allow to sweep from the regime of perturbative ultraviolet completion to the non-linear one assumed in models in which the Higgs particle is a low-energy remnant of some strong dynamics. We analyze the phenomenological implications and constraints from precision observables and LHC data. Furthermore, we derive the d <= 6 effective Lagrangian in the limit of heavy exotic fermions.