Electroweak phase transition in the scale invariant standard model

In an extension to the scale invariant standard model by two real singlet scalars s and s′ in addition to the Higgs field, we investigate the strong first-order electroweak phase transition as a requirement for baryogenesis. This is the minimal extension to the scale invariant standard model with two extra degrees of freedom that possesses the physical Higgs mass of 125 GeV. The scalar s′ being stable because of the Z2 discrete symmetry is taken as the dark matter candidate. We then show that the electroweak phase transition is strongly first order, the dark matter relic density takes the desired value ΩDMh2 ∼ 0.11, and the constraints from direct detection experiments are respected only if ms′ ≡ mDM ≳ 4.5 TeV. The model also puts a lower bound on the scalon mass, ms ≳ 200 GeV.