Higgs boson coupling to a new strongly interacting sector

TL;DR

This paper investigates how a Higgs boson interacts with a new strongly interacting sector involving composite particles, analyzing experimental constraints and implications for model parameters within a generic effective field theory framework.

Contribution

It provides a detailed analysis of constraints on composite Higgs models with heavy vectors, highlighting the conditions for compatibility with current experimental data.

Findings

Constraints from Zbar{b} vertex and Higgs mass are significant.

Higgs diphoton decay and oblique parameters impose weak constraints.

Heavy vector resonances should couple weakly to quarks for model viability.

Abstract

In the framework of strongly interacting dynamics for electroweak symmetry breaking, heavy composite particles may arise and cause observable effects, as they should couple strongly to the resulting Higgs boson and affect the signals that appear at one loop level. Here we study this expected behavior, contrasting it with current experimental knowledge. We work in a simple and generic scenario where the lowest lying composite states are the Higgs scalar doublet and a massive vector triplet. We use an effective chiral Lagrangian to describe the theory below the compositeness scale $\Lambda$, assumed to be $4\pi v \simeq~3$ TeV. The effective theory contains the Standard Model spectrum and the extra composites. We determine the constraints on this scenario imposed by our current knowledge of the $Zb\bar{b}$ vertex, the $T$ and $S$ oblique parameters, and the recently measured Higgs mass and its diphoton decay rate. We found that the $T$ and $S$ parameters as well as the Higgs diphoton decay do not provide important constraints on the model. In contrast, the constraints arising from the $Zb\bar{b}$ vertex and from the Higgs mass at $126$ GeV are fulfilled only if the heavy vector resonances do not couple strongly with quarks, and at the same time the Higgs boson has a moderate but not too strong coupling to the heavy composite resonances.