Dark matter in the classically conformalB−Lmodel

Abstract

When the classically conformal invariance is imposed on the minimal gauged B − L extended Standard Model (SM), the B − L gauge symmetry is broken by the Coleman-Weinberg mechanism naturally at the TeV scale. Introducing a new Z 2 parity in the model, we investigate phenomenology of a right-handed neutrino dark matter whose stability is ensured by the parity. We find that the relic abundance of the dark matter particle can be consistent with the observations through annihilation processes enhanced by resonances of either the SM Higgs boson, the B − L Higgs boson or the B − L gauge boson (Z' boson). Therefore, the dark matter mass is close to half of one of these boson masses. Due to the classically conformal invariance and the B − L gauge symmetry breaking via the Coleman-Weinberg mechanism, Higgs boson masses, Z' boson mass and the dark matter mass are all related, and we identify the mass region to be consistent with experimental results. We also calculate the spin-independent cross section of the dark matter particle off with nucleon and discuss implications for future direct dark matter search experiments.

Right-handed neutrino dark matter under the B − L gauge interaction

“…In this limit, which might invoke a flavor symmetry like refs. [38][39][40], the lightest neutrino would be massless (m ν 1 = 0) or almost massless, which is still consistent with the experimental constraints [50]. Throughout the rest of this paper, we will discuss in the zero N 1 mixing angle (θ 1 = 0) limit, which also allows us to leave out of account the constraints from the X-ray observations with the N 1 → γ + ν process.…”

“…However, since an effective operator of the Z mediation is given by (N 1 γ 5 γ µ N 1 )(qγ µ q), the scattering cross section is suppressed by velocity or momentum in the non-relativistic limit [84], which makes the measurement of this process difficult. We do not consider the S mediated process [39,40] as this interaction is turned off by taking λ HS 0 in this paper. Next, let us discuss possible experiments to test the freeze-in region with the right relic density (roughly, g B−L ∼ 10 −6 region) in figure 2.…”

“…[38][39][40]. They impose a Z 2 protective symmetry on some sterile neutrino while requiring two others to accommodate realistic neutrino phenomenology.…”

“…In our study, the most interesting case (also the main case) actually is a very light RHN which does not necessarily call for a Z 2 protective symmetry, although for the sake of a global picture we also include the heavy RHN dark matter case, which then may require a flavor symmetry as in refs. [38][39][40]. We also exploit the freeze-in mechanism to account for correct relic density for the RHN DM.…”

Phase transition and gravitational wave phenomenology of scalar conformal extensions of the Standard Model

“…Phase transitions which directly or indirectly result in the generation of the electroweak scale have also been analysed within the framework of classically conformal (or scale invariant) models [30,[32][33][34][35][36][37], often in connection to other open problems of contemporary physics such as the origins of Dark Matter (DM) and the inflationary dynamics [31,32,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. An important feature of classically conformal models is that the phase transition associated to the insurgence of the electroweak scale is generally of the first order and very strong.…”