Electroweak baryogenesis and dark matter from a singlet Higgs

TL;DR

This paper explores how a singlet scalar coupled to the Higgs can induce a strong electroweak phase transition, enable baryogenesis, and serve as a dark matter candidate with specific experimental signatures.

Contribution

It demonstrates that a singlet scalar can facilitate electroweak baryogenesis and act as a dark matter candidate, with analytical phase transition properties and testable direct detection signals.

Findings

Electroweak phase transition can be strongly first-order with a singlet scalar.

CP violation from a dimension-6 operator enables baryogenesis.

Singlet dark matter has a mass between 80-160 GeV and interacts near current detection limits.

Abstract

If the Higgs boson H couples to a singlet scalar S via lambda_m |H|^2 S^2, a strong electroweak phase transition can be induced through a large potential barrier that exists already at zero temperature. In this case properties of the phase transition can be computed analytically. We show that electroweak baryogenesis can be achieved using CP violation from a dimension-6 operator that couples S to the top-quark mass, suppressed by a new physics scale that can be well above 1 TeV. Moreover the singlet is a dark matter candidate whose relic density is < 3% of the total dark matter density, but which nevertheless interacts strongly enough with nuclei (through Higgs exchange) to be just below the current XENON100 limits. The DM mass is predicted to be in the range 80-160 GeV.