A Natural Two-Higgs-Doublet Model

TL;DR

This paper explores the phenomenological implications of canceling one-loop quadratic divergences in Two-Higgs-Doublet Models, identifying parameter regions that address the little hierarchy problem and allow for CP violation and dark matter candidates.

Contribution

It provides a detailed analysis of parameter space in 2HDMs that achieve divergence cancellation, including the introduction of a scalar singlet for dark matter and implications for the little hierarchy problem.

Findings

Inert Doublet Model cannot satisfy divergence cancellation.

Allowed parameter regions with divergence cancellation are identified.

Scalar singlet extension can raise the cutoff scale to over 15 TeV.

Abstract

We discuss phenomenological consequences of requiring the cancellation of one-loop quadratic divergences in corrections to scalar masses within Two-Higgs-Doublet Models (2HDM). It is shown that the Inert Doublet Model (IDM) can not accommodate the requirement of the cancellation. A general 2HDM is also analyzed taking into account existing experimental constraints. Allowed regions in the parameter space, permitting the above cancellation, are determined. A degeneracy between masses of scalar bosons is observed for tanbeta \gsim 40. The possibility for CP violation in the scalar potential is discussed and regions of tanbeta-M_{H^\pm} with substantial amount of CP violation are determined. In order to provide a source for dark matter in a minimal manner, a scalar gauge singlet is introduced and discussed. The model allows to ameliorate the little hierarchy problem by lifting the minimal scalar Higgs boson mass and by suppressing the one-loop quadratic corrections to scalar masses. The cutoff originating from the naturality arguments is therefore lifted to \gsim 15 TeV depending on the mass of the lightest scalar.