Real Higgs singlet and the electroweak phase transition in the standard model

Abstract

The effective potential at finite temperature is constructed within the minimal standard model when a real Higgs singlet is added on. We find that a region of parameter space exists for which one can find a first order transition strong enough to prevent the erasure due to sphalerons of baryon asymmetry, while keeping the mass of the smallest Higgs boson above the experimental lower bound of about 60GeV.

Singlet Higgs phenomenology and the electroweak phase transition

“…Our analysis of the EWPT that leads to these phenomenological implications builds on extensive, previous work by others, both in the case of singlet scalar models [21,23,24] and supersymmetric models with an extended scalar sector [15,16]. In carrying out the present study, we have tried to amplify on earlier work by identifying general features of singlet scalar extensions that lead to a strong first order EWPT and that should apply to a broad array of specific models.…”

“…Similarly, one has 24) where the thermal masses M 2 k (ϕ, α, T ) are given in terms of the T = 0 masses and the finite temperature mass functions, Π k :…”

“…In the case of the Standard Model, these considerations imply thatλ 0 /g 2 1, where g 2 ≈ 0.4. One may obtain further restrictions on the value of a 2 by requiring perturbativity up to a scale Λ that defines the limit of the validity of the theory, as has been implemented by Espinosa and Quiros in the case of the complex scalar model mentioned above [24]. A detailed analysis of perturbativity considerations goes beyond the scope of the present study, where our focus falls on identifying general trends and for which limiting the ranges of the dimensionless parameters as in Table 1 should suffice 7 .…”

First order electroweak phase transition from (non)conformal extensions of the standard model

“…Depending on the values of the model parameters the phase structure and the vacuum structure can be very rich. We shall not make a full EWPT analysis for this general model here, as it can be found from the literature [3,[28][29][30][31][32] (see also [33]). A thorough investigation of the potential structure, yielding a strong first order phase transition stemming already from the tree level potential, once the leading finite temperature terms are taken into account, was recently performed in [3].…”

Sphalerons in the standard model with a real Higgs singlet

“…In this paper I consider the sphaleron solutions in the minimal SM augumented by a real singlet Higgs field. This model was shown to be capable of satisfying at least one of the several conditions needed for electroweak baryogenesis, namely the condition that any baryon asymmetry created at a first order phase transition does not get washed away by subsequent sphaleron processes [4]. This model is interesting due to the existence of tree-level trilinear Higgs couplings which seem to enhance the possibility of satisfying this condition (I also point out other possible interest this model has in this regard in the discussions later).…”