Complex Scalar Singlet Dark Matter: Vacuum Stability and Phenomenology

TL;DR

This paper investigates the stability, phenomenology, and experimental constraints of a complex scalar singlet extension of the Standard Model, highlighting conditions under which the model remains viable or is ruled out based on vacuum stability and collider data.

Contribution

It provides a gauge-invariant analysis of vacuum stability in the complex singlet scalar extension and compares it with traditional gauge-dependent methods, offering new insights into model viability.

Findings

Both Higgs-like and lighter singlet scalars are compatible with current experimental data if new physics appears at TeV scale.

Vacuum stability constraints can be compatible with collider constraints under certain conditions.

Potential tension exists between vacuum stability and electroweak precision data if no new physics is found until higher energy scales.

Abstract

We analyze one-loop vacuum stability, perturbativity, and phenomenological constraints on a complex singlet extension of the Standard Model (SM) scalar sector containing a scalar dark matter candidate. We study vacuum stability considerations using a gauge-invariant approach and compare with the conventional gauge-dependent procedure. We show that, if new physics exists at the TeV scale, the vacuum stability analysis and experimental constraints from the dark matter sector, electroweak precision data, and LEP allow both a Higgs-like scalar in the mass range allowed by the latest results from CMS and ATLAS and a lighter singlet-like scalar with weak couplings to SM particles. If instead no new physics appears until higher energy scales, there may be significant tension between the vacuum stability analysis and phenomenological constraints (in particular electroweak precision data) to the extent that the complex singlet extension with light Higgs and singlet masses would be ruled out. We comment on the possible implications of a scalar with ~125 GeV mass and future ATLAS invisible decay searches.