Baryogenesis in the two doublet and inert singlet extension of the Standard Model

TL;DR

This paper explores an extended Standard Model with two Higgs doublets and a singlet scalar, demonstrating its potential for a strong first-order phase transition that explains baryogenesis and possibly dark matter, while satisfying experimental constraints.

Contribution

It introduces a novel two-doublet plus singlet scalar model that facilitates baryogenesis and dark matter considerations with a unique phase transition pattern.

Findings

Model allows a strongly first-order phase transition compatible with baryogenesis.

Singlet scalar can serve as a dark matter candidate, albeit with lower abundance.

Transition dynamics involve supercooling and low nucleation temperatures.

Abstract

We investigate an extension of the Standard Model containing two Higgs doublets and a singlet scalar field (2HDSM). We show that the model can have a strongly first-order phase transition and give rise to the observed baryon asymmetry of the Universe, consistent with all experimental constraints. In particular, the constraints from the electron and neutron electric dipole moments are less constraining here than in pure two-Higgs-doublet model (2HDM). The two-step, first-order transition in 2HDSM, induced by the singlet field, may lead to strong supercooling and low nucleation temperatures in comparison with the critical temperature, $T_n \ll T_c$, which can significantly alter the usual phase-transition pattern in 2HD models with $T_n \approx T_c$. Furthermore, the singlet field can be the dark matter particle. However, in models with a strong first-order transition its abundance is typically but a thousandth of the observed dark matter abundance.