Inert scalars and vacuum metastability around the electroweak scale

TL;DR

This paper investigates how adding a heavy scalar doublet to the Standard Model affects vacuum stability around the electroweak scale, revealing potential destabilization effects and constraints in inert doublet models.

Contribution

It provides a detailed analysis of vacuum stability in extended scalar sectors, highlighting the destabilizing impact of inert scalars and the incompatibility with experimental constraints.

Findings

Heavy scalars can destabilize the electroweak vacuum.

Inert doublet models cannot reconcile vacuum metastability with experimental constraints.

Additional scalars may introduce new minima affecting electroweak symmetry breaking.

Abstract

We analyse effective potential around the electroweak (EW) scale in the Standard Model extended with a heavy scalar doublet. We show that the additional scalars can have a strong impact on vacuum stability. Although the additional heavy scalars may improve the behaviour of running Higgs self-coupling at large field values, we prove that they can destabilise the vacuum due to EW-scale effects. A new EW symmetry conserving minimum of the effective potential can appear rendering the electroweak symmetry breaking minimum meta- or unstable. However, for the case of the inert doublet model (IDM) with a 125 GeV Higgs boson we demonstrate that the parameter space region where the vacuum is meta- or unstable cannot be reconciled with the constraints from perturbative unitarity, electroweak precision tests and dark matter relic abundance measurements.