A complex singlet extension of the Standard Model and Multi-critical Point Principle

TL;DR

This paper explores a complex singlet extension of the Standard Model, demonstrating that a strong first-order electroweak phase transition can occur under the Multi-critical Point Principle, with implications for dark matter and collider phenomenology.

Contribution

It introduces the application of the Multi-critical Point Principle to the complex singlet scalar extension of the Standard Model, analyzing its effects on phase transitions and scalar mass degeneracy.

Findings

Strong first-order electroweak phase transition is possible under MPP due to 1-loop corrections.

Parameter space with degenerate scalar masses can evade dark matter detection constraints.

Non-degenerate scalar scenarios are also viable and studied for comparison.

Abstract

We study the Multi-critical Point Principle (MPP) in a complex singlet scalar extension of the Standard Model (CxSM). The MPP discussed in this study selects model parameters so that two low-energy vacua realized by scalar fields are degenerate. We further note that the MPP may inhibit the electroweak phase transition (EWPT) in a certain class of models where the tree-level potential plays an essential role in its realization. Despite that, we show that strong first-order EWPT still occurs even after imposing the MPP to the scalar potential of the CxSM due to the 1-loop corrections by the new scalar boson. We study the allowed parameter space where a mass of the additional scalar is degenerate with that of the Standard Model Higgs boson, which provides a built-in mechanism to circumvent constraints from dark matter direct detection experiments. The parameter space for the non-degenerate scalar scenario is also studied for comparison.