Abstract
In this work we study a classically scale invariant extension of the Standard Model that can explain simultaneously dark matter and the baryon asymmetry in the universe. In our set-up we introduce a dark sector, namely a non-Abelian SU(2) hidden sector coupled to the SM via the Higgs portal, and a singlet sector responsible for generating Majorana masses for three right-handed sterile neutrinos. The gauge bosons of the dark sector are mass-degenerate and stable, and this makes them suitable as dark matter candidates. Our model also accounts for the matter-anti-matter asymmetry. The lepton flavour asymmetry is produced during CP-violating oscillations of the GeV-scale right-handed neutrinos, and converted to the baryon asymmetry by the electroweak sphalerons. All the characteristic scales in the model: the electro-weak, dark matter and the leptogenesis/neutrino mass scales, are generated radiatively, have a common origin and related to each other via scalar field couplings in perturbation theory.
Highlights
Where Φ denotes the SU(2)DM doublet, H is the SM Higgs doublet, and σ is a gauge-singlet introduced in order to generate the Majorana masses for the sterile neutrinos, and the visible neutrinos masses and mixings via the see-saw mechanism
Later on we shall see that the most interesting region in parameter space leading to both the correct dark matter abundance and the correct baryon asymmetry is for σ φ and one can think of σ as a Coleman-Weinberg scalar that once it acquires a non-zero vev it will be communicated to φ and h through the portal couplings λφσ and λhσ
We carried out a scan over all free parameters in our model to determine the region of the parameter space where the leptogenesis mechanism outlined above can generate the observed baryon asymmetry
Summary
The scalar field content of our model consists of an SU(2)L doublet H, an SU(2)DM doublet Φ and a real scalar σ; the latter giving mass to the sterile neutrinos after acquiring a vev in similar fashion to Ref. [10]. The scalar field content of our model consists of an SU(2)L doublet H, an SU(2)DM doublet Φ and a real scalar σ; the latter giving mass to the sterile neutrinos after acquiring a vev in similar fashion to Ref. Working in the unitary gauge of the SU(2)L×SU(2)DM, the two scalar doublets in the theory are reduced to,. There are no mass scales appearing in the classical theory, and at the origin in the field space, all scalar vevs are zero, in agreement with classical scale invariance. We impose a conservative constraint on all the scalar couplings for the model to be perturbative |λi| < 3, we impose gDM < 3 and in order to ensure vacuum stability the following set of constraints need to be satisfied, λh ≥ 0, λφ ≥ 0, λσ ≥ 0, λhφ ≤ 1, − √λhσ ≤ 1, λφσ ≤ 1,.
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