Conformal vector dark matter and strongly first-order electroweak phase transition

Abstract

We study a conformal version of the Standard Model (SM), which apart from SM sector, containing a U D (1) dark sector with a vector dark matter candidate and a scalar field (scalon). In this model the dark sector couples to the SM sector via a Higgs portal. The theory is scaleinvariant in lowest order, therefore the spontaneous symmetry breaking of scale invariance entails the existence of a scalar particle, scalon, with vanishing zeroth-order mass. However, one-loop corrections break scale invariance, so they give mass to the scalon. Because of the scale invariance, our model is subjected to constraints which remove many of the free parameters. We put constraints to the two remaining parameters from the Higgs searches at the LHC, dark matter relic density and dark matter direct detection limits by PandaX-II. The viable mass region for dark matter is about 1-2 TeV. We also obtain the finite temperature one-loop effective potential of the model and demonstrate that finite temperature effects, for the parameter space constrained by dark matter relic density, induce a strongly first-order electroweak phase transition. * syaser.ayazi@semnan.ac.ir † a.mohamadnejad@ut.ac.ir and fermionic loop contributions to the Higgs mass within supersymmetry can also explain the hierarchy problem. However, concerning the null results at the first and second LHC runs [3,4], and other popular theoretical resolutions of the hierarchy problem, such as large extra dimensions, investigating alternative approaches are appealing.As it was mentioned, one approach of addressing the hierarchy problem is the radical assumption that the fundamental theory describing Nature does not have any scale. This idea is well worth considering for its potential to be an sparing solution to the hierarchy problem. The CW mechanism with a Higgs does not work for the electroweak symmetry breaking because the large top mass does not permit radiative breaking of the electroweak symmetry, but, simple extensions of the Higgs sector with additional bosonic degrees of freedom are known to be phenomenologically viable (see, e.g., ). On the other hand, the scale-invariant extension of the Higgs sector, is a generic feature of many DM models with scalar [27][28][29][30][31][32][33][34][35][36][37][38], fermionic [39][40][41][42][43][44][45] and vector [46-52] DM candidates.There are plenty astronomical and cosmological evidences that around 27 percent of the Universe is made of DM. According to the dominant paradigm, DM consists of weakly interacting massive particles (WIMPs) that successfully explain the large scale structures in our Universe.However, the nature of DM is not well understood, and its particle properties such as spin, mass and interactions all are unknown. Therefore, it is not surprising that despite many previous models, there are still opportunities for DM model building.In this paper we consider spin one (vector) gauge fields as DM candidates. Without concerning scale invariance, vector DM [53-72] and some of its theoretical and phenomenological aspe...

Gravitational waves from scale-invariant vector dark matter model: probing below the neutrino-floor

“…As it is seen, for a narrow region of parameter space, DM-nucleon cross section has a dip below the neutrino-floor. The origin of this dip, is the proportionality of DM-nucleon cross section with ( 1 [11]. Therefore, for the parameter space around m ϕ m h , we expect such a dip.…”

“…We have recently studied the DM phenomenology of such a model [11]. Here we briefly report the main results.…”

“…Then the quantum effects must have broken the scale-invariant symmetry, generating a nonzero VEV of the scalar field(s) and all the mass terms of massive particles via Coleman-Weinberg mechanism [7]. Particularly, conformal DM models with Higgs portal are attractive because they can solve DM problem and at the same time can generate a strongly first order phase transition [8][9][10][11]. GWs due to first order phase transition have been studied within models where the scale-invariant symmetry is broken due to Coleman-Weinberg mechanism [12][13][14][15][16][17][18][19][20] or models with DM candidate [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].…”

“…In this paper, we will study a conformal model [11] which is well motivated from a DM perspective or by naturalness arguments. The model is a scale-invariant extension of the SM, enlarged by a dark U (1) D gauge symmetry which provides a viable vector DM candidate.…”

Vector self-interacting dark matter

“…Simple constructions with a su(2) gauge group provide degenerate, massive spin-1 particles that can be stable due to custodial symmetry [21,23,24]. Other models are based on the spontaneous breaking of scale invariance [33][34][35][36][37][38][39][40]. The scalar field that breaks the gauge symmetry may be used as a portal to the visible sector by mixing with the Standard Model Higgs; the amount of mixing controls the signal at direct detection experiments.…”