Doublet-singlet model and unitarity

TL;DR

This paper investigates a singlet-doublet fermionic extension of the Standard Model, analyzing its mass spectrum, dark matter candidate stability, and unitarity constraints on Yukawa couplings.

Contribution

It provides analytic formulas for the mass spectrum near blind spots and establishes unitarity bounds on the Yukawa couplings in the model.

Findings

Analytic expressions for mass spectrum at blind spots.

Perturbative unitarity bounds on Yukawa couplings.

Constraints on dark matter interactions with Higgs and Z bosons.

Abstract

We study the renormalizable singlet-doublet fermionic extension of the Standard Model. In this model, the new vector-like fermions couple to the gauge bosons and to the Higgs via new Yukawa couplings, that allow for nontrivial mixing in the new sector, providing a stable, neutral dark matter candidate. Approximate analytic formulae are given for the mass spectrum around the blind spots, where the dark matter candidate coupling to $h$ or $Z$ vanishes. We calculate the two particle scattering amplitudes in the model, impose the perturbative unitarity constraints and establish bounds on the Yukawa couplings.