Gravitational waves and electroweak baryogenesis in a global study of the extended scalar singlet model

TL;DR

This paper conducts a comprehensive analysis of an extended scalar singlet model with fermionic dark matter, exploring its viability for electroweak baryogenesis and gravitational wave signals, constrained by current experimental data.

Contribution

It provides the first global fit of the model incorporating dark matter, collider, and electroweak data, identifying parameter regions compatible with baryogenesis and detectable gravitational waves.

Findings

Model can achieve strong first-order phase transition and match dark matter relic density.

Viable parameter space predicts gravitational wave signals within reach of future detectors.

Strong bounds on scalar and fermion masses from combined experimental constraints.

Abstract

We perform a global fit of the extended scalar singlet model with a fermionic dark matter (DM) candidate. Using the most up-to-date results from the $\mathit{Planck}$ measured DM relic density, direct detection limits from the XENON1T (2018) experiment, electroweak precision observables and Higgs searches at colliders, we constrain the 7-dimensional model parameter space. We also find regions in the model parameter space where a successful electroweak baryogenesis (EWBG) can be viable. This allows us to compute the gravitational wave (GW) signals arising from the phase transition, and discuss the potential discovery prospects of the model at current and future GW experiments. Our global fit places a strong upper $\mathit{and}$ lower limit on the second scalar mass, the fermion DM mass and the scalar-fermion DM coupling. In agreement with previous studies, we find that our model can simultaneously yield a strong first-order phase transition and saturate the observed DM abundance. More importantly, the GW spectra of viable points can often be within reach of future GW experiments such as LISA, DECIGO and BBO.