Higgs Low-Energy Theorem (and its corrections) in Composite Models

TL;DR

This paper extends the Higgs low-energy theorem to composite models, analyzing its accuracy and corrections for single and double Higgs production, and performs a detailed one-loop calculation in the minimal composite Higgs model, considering fermionic resonances and experimental constraints.

Contribution

It generalizes the Higgs low-energy theorem for nonlinear interactions in composite models and provides a comprehensive one-loop analysis including fermionic resonances.

Findings

The theorem approximates single Higgs production within a few percent.

Double Higgs production receives about 50% correction.

Fermionic resonances significantly affect the gg->hh cross section.

Abstract

The Higgs low-energy theorem gives a simple and elegant way to estimate the couplings of the Higgs boson to massless gluons and photons induced by loops of heavy particles. We extend this theorem to take into account possible nonlinear Higgs interactions resulting from a strong dynamics at the origin of the breaking of the electroweak symmetry. We show that, while it approximates with an accuracy of order a few percents single Higgs production, it receives corrections of order 50% for double Higgs production. A full one-loop computation of the gg->hh cross section is explicitly performed in MCHM5, the minimal composite Higgs model based on the SO(5)/SO(4) coset with the Standard Model fermions embedded into the fundamental representation of SO(5). In particular we take into account the contributions of all fermionic resonances, which give sizeable (negative) corrections to the result obtained considering only the Higgs nonlinearities. Constraints from electroweak precision and flavor data on the top partners are analyzed in detail, as well as direct searches at the LHC for these new fermions called to play a crucial role in the electroweak symmetry breaking dynamics.