Unravelling an extended quark sector through multiple Higgs production?

TL;DR

This paper investigates how extended quark sectors in new physics models affect double Higgs production via gluon fusion, providing exact calculations and analyzing experimental constraints to understand deviations from the Standard Model.

Contribution

It offers exact leading-order calculations of double Higgs production in models with extra quarks and links these to effective operators and experimental bounds.

Findings

Double Higgs production rates are tightly constrained by electroweak and Higgs decay measurements.

Extended quark models can mimic Standard Model Higgs phenomenology despite modifications.

Dimension six operators significantly influence gluon-fusion Higgs production.

Abstract

In many new physics scenarios, the particle content of the Standard Model is extended and the Higgs couplings are modified, sometimes without affecting single Higgs production. We analyse two models with additional quarks. In these models, we compute double Higgs production from gluon fusion exactly at leading-order, and present analytical results in the heavy-quark mass ap- proximation. The experimental bounds from precision electroweak measurements and from the measured rate of single Higgs production combine to give significant restrictions for the allowed deviation of the double Higgs production rate from the Standard Model prediction as well as on the branching ratio for the Higgs decay into photons. The two models analysed eventually present a similar Higgs phenomenology as the Standard Model. We connect this result to the magnitude of the dimension six operators contributing to the gluon-fusion Higgs production.