Complementarity of the future $e^+ e^-$ colliders and gravitational waves in the probe of complex singlet extension to the Standard Model

TL;DR

This paper explores how future electron-positron colliders and gravitational wave detectors can jointly probe the complex singlet extension of the Standard Model, which can explain dark matter and a strong electroweak phase transition.

Contribution

It provides a comprehensive analysis of the complementarity between collider experiments and gravitational wave observations in testing the complex singlet scalar extension of the Standard Model.

Findings

Future $e^+ e^-$ colliders can test benchmark models of the cxSM.

Gravitational wave detectors like LISA can probe models beyond collider sensitivity.

The combination enhances the discovery potential for new physics related to dark matter and phase transitions.

Abstract

In this work, we study the future probes of the complex singlet extension to the Standard Model (cxSM). This model is possible to realize a strongly first-order electroweak phase transition (SFOEWPT). The cxSM naturally provides dark matter (DM) candidate, with or without an exact $\mathbb{Z}_2$ symmetry in the scalar sector. The benchmark models which can realize the SFOEWPT are selected, and passed to the current observational constraints to the DM candidates, including the relic densities and the direct detection limits set by the latest XENON1T results. We then calculate the one-loop corrections to the SM-like Higgs boson decays and the precision electroweak parameters due to the cxSM scalar sector. We perform a global fit to the benchmark models and study the extent to which they can be probed by the future high-energy $e^+ e^-$ colliders, such as CEPC and FCC-ee. Besides, the gravitational wave (GW) signals generated by the benchmark models are also evaluated. We further find that the future GW detector, such as LISA, is complementary in probing the benchmark models that are beyond the sensitivity of the future precision tests at the $e^+ e^-$ colliders.