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# Enhancement of the H±W∓Z vertex in the three scalar doublet model

Moretti, Stefano, Rojas, Diana and Yagyu, Kei (2015) Enhancement of the H±W∓Z vertex in the three scalar doublet model. Journal of High Energy Physics, 2015 (08), [116].

Record type: Article

## Abstract

We compute one-loop induced trilinear vertices with physical charged Higgs bosons $H^\pm$ and ordinary gauge bosons, i.e., $H^\pm W^\mp Z$ and $H^\pm W^\mp \gamma$, in the model with two active plus one inert scalar doublet fields under a $Z_2(\text{unbroken})\times \tilde{Z}_2(\text{softly-broken})$ symmetry. The $Z_2$ and $\tilde{Z}_2$ symmetries are introduced to guarantee the stability of a dark matter candidate and to forbid the flavour changing neutral current at the tree level, respectively. The dominant form factor $F_Z$ of the $H^\pm W^\mp Z$ vertex can be enhanced by non-decoupling effects of extra scalar boson loop contributions. We find that, in such a model, $|F_Z|^2$ can be one order of magnitude larger than that predicted in two Higgs doublet models under the constraints from vacuum stability, perturbative unitarity and the electroweak precision observables. In addition, the branching fraction of the $H^\pm \to W^\pm Z$ $(H^\pm \to W^\pm \gamma)$ mode can be of order 10~(1)\% level when the mass of $H^\pm$ is below the top quark mass. Such a light $H^\pm$ is allowed by the so-called Type-I and Type-X Yukawa interactions which appear under the classification of the $\tilde{Z}$ charge assignment of the quarks and leptons. We also calculate the cross sections for the processes $H^\pm \to W^\pm Z$ and $H^\pm \to W^\pm \gamma$ onset by the top quark decay $t\to H^\pm b$ and electroweak $H^\pm$ production at the LHC.

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Accepted/In Press date: 5 August 2015
Published date: 24 August 2015
Keywords: hep-ph
Organisations: Theory Group

## Identifiers

Local EPrints ID: 411847
URI: http://eprints.soton.ac.uk/id/eprint/411847
ISSN: 1029-8479
PURE UUID: 0b9216cf-1669-4923-bbea-f40ddb0b40e5

## Catalogue record

Date deposited: 27 Jun 2017 16:31

## Contributors

Author: Stefano Moretti
Author: Diana Rojas
Author: Kei Yagyu