Standard Model with a Complex Scalar Singlet: Cosmological Implications and Theoretical Considerations

TL;DR

This paper investigates the complex scalar singlet extension of the Standard Model, focusing on its implications for electroweak phase transition and dark matter, using a gauge-invariant approach and renormalization group improvements.

Contribution

It introduces a gauge-invariant, renormalization group improved analysis of the complex scalar singlet model, refining the parameter space for electroweak phase transition and dark matter compatibility.

Findings

Parameter space for strong first order electroweak phase transition is restricted.

Dark matter mass near half of Higgs boson mass is favored.

Recent LUX data constrains dark matter properties in this model.

Abstract

We analyze the theoretical and phenomenological considerations for the electroweak phase transition and dark matter in an extension of the Standard Model with a complex scalar singlet (cxSM). In contrast with earlier studies, we use a renormalization group improved scalar potential and treat its thermal history in a gauge invariant manner. We find that the parameter space consistent with a strong first order electroweak phase transition (SFOEWPT) and present dark matter phenomenological constraints is significantly restricted compared to results of a conventional, gauge non-invariant analysis. In the simplest variant of the cxSM, recent LUX data and a SFOEWPT require a dark matter mass close to half the mass of the Standard Model-like Higgs boson. We also comment on various caveats regarding the perturbative treatment of the phase transition dynamics.