# Lepton Portal Limit of Inert Higgs Doublet Dark Matter with Radiative Neutrino Mass

## TL;DR

This paper explores an extension of the Inert Higgs Doublet Model incorporating right-handed neutrinos and heavy leptons, demonstrating how lepton portal interactions can account for dark matter relic abundance with suppressed Higgs interactions, and discussing experimental implications.

## Contribution

It introduces a novel lepton portal mechanism within the inert Higgs doublet framework that explains dark matter abundance with minimal Higgs coupling, linking neutrino mass generation and collider phenomenology.

## Key findings

- Lepton portal interactions can produce correct dark matter relic density with tiny Higgs couplings.
- Suppressed Higgs portal interactions lead to low dark matter-nucleon cross sections.
- The model predicts small invisible Higgs decay widths, testable at future experiments.

## Abstract

We study an extension of the Inert Higgs Doublet Model (IHDM) by three copies of right handed neutrinos and heavy charged leptons such that both the inert Higgs doublet and the heavy fermions are odd under the $Z_2$ symmetry of the model. The neutrino masses are generated at one loop in the scotogenic fashion. Assuming the neutral scalar of the inert Higgs to be the dark matter candidate, we particularly look into the region of parameter space where dark matter relic abundance is primarily governed by the inert Higgs coupling with the leptons. This corresponds to tiny Higgs portal coupling of dark matter as well as large mass splitting within different components of the inert Higgs doublet suppressing the coannihilations. Such lepton portal couplings can still produce the correct relic abundance even if the Higgs portal couplings are arbitrarily small. Such tiny Higgs portal couplings may be responsible for suppressed dark matter nucleon cross section as well as tiny invisible branching ratio of the standard model Higgs, to be probed at ongoing and future experiments. We also briefly discuss the collider implications of such a scenario.