Classically conformal B-L extended Standard Model and phenomenology

Bardeen has argued that once the classically conformal invariance and its minimal violation by quantum anomalies are imposed on the SM, it can be free from the quadratic divergences and hence the gauge hierarchy problem. Under the hypothesis, We investigated the minimal B-L extended SM with a flat Higgs potential at the Planck scale. In this model, the B-L symmetry is radiatively broken at TeV scale. We studied phenomenology and detectability of the model at LHC and the ILC.Comment: 4 pages, 3 figures, Toyama International Workshop on Higgs as a Probe of New Physics 201

The classically conformal B−-L extended Ma model

We discuss a classically conformal radiative seesaw model with gauged B$-$L symmetry, in which the B$-$L symmetry breaking can occur through the Coleman-Weinberg mechanism. As a result, all mass terms are generated and EW symmetry breaking also occurs. We show some allowed parameters to satisfy several theoretical constraints.Comment: 4 pages, 2 figures, proceedings of Toyama International Workshop on Higgs as a Probe of New Physics 201

Radiative Neutrino Model with Inert Triplet Scalar

We study a one-loop induced radiative neutrino model with an inert isospin triplet scalar field, in which we discuss current neutrino oscillation data, lepton flavor violations, muon anomalous magnetic moment, and a dark matter candidate. We show global analysis combining all the constraints, and briefly mention another possibility.Comment: 21 pages, 3 figures, 3 tables, references added. Accepted version for publication in Physical Review D, discussion of mu-e conversion is added and the part of relic density are modified. arXiv admin note: text overlap with arXiv:1509.0406

Two-loop Neutrino Model with Exotic Leptons

We propose a two-loop induced neutrino mass model, in which we show some bench mark points to satisfy the observed neutrino oscillation, the constraints of lepton flavor violations, and the relic density in the co-annihilation system satisfying the current upper bound on the spin independent scattering cross section with nuclei. We also discuss new sources of muon anomalous magnetic moment.Comment: 20 pages, 1 figure, 4 table

X-ray line in Radiative Neutrino Model with Global U(1)U(1) Symmetry

We study a three loop induced radiative neutrino model with global $U(1)$ symmetry at TeV scale, in which we consider two component dark matter particles. We discuss the possibility to explain the X-ray line signal at about 3.55 keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy. Subsequently, we also discuss to show that sizable muon anomalous magnetic moment, a discrepancy of the effective number of neutrino species $\Delta N_{\rm eff}\approx$ 0.39, and scattering cross section detected by direct detection searches can be derived.Comment: 14 pages, 3 figures, 1 table; version accepted for publication in Physical Review

TeV Scale B-L model with a flat Higgs potential at the Planck scale -- in view of the hierarchy problem

The recent discovery of the Higgs-like particle at around 126 GeV has given us a big hint towards the origin of the Higgs potential. Especially the running quartic coupling vanishes near the Planck scale, which indicates a possible link between the physics in the electroweak and the Planck scales. Motivated by this and the hierarchy problem, we investigate a possibility that the Higgs has a flat potential at the Planck scale. In particular, we study the RG analysis of the B-L extension of the standard model with a classical conformality. The B-L symmetry is radiatively broken at the TeV scale via the Coleman-Weinberg mechanism. The electroweak symmetry breaking is triggered by a radiatively generated scalar mixing so that its scale 246 GeV is dynamically related with the B-L breaking scale at TeV. The Higgs boson mass is given at the border of the stability bound,which is lowered by a few GeV from the SM by the effect of the B-L gauge interaction.Comment: 18 pages, 5 figures; report number change

A Two Loop Radiative Neutrino Model

We explore the possibility to explain a bosonic dark matter candidate with a gauge singlet inside the loop to generate the neutrino mass matrix at two-loop level. The mass matrix is suppressed by a small mixing that comes from the bound on {direct detection experiments of the dark matter, and equivalent of the three-loop neutrino model due to the small mixing between neutral inert bosons. Here, our setup is} the Zee-Babu type scenario with $Z_3$ discrete symmetry, in which we consider the neutrino oscillation data, lepton flavor violations, muon $g-2$, $\mu-e$ conversion rate, lepton flavor-changing and conserving $Z$ boson decay and bosonic dark matter candidate.Comment: 16 pages, 5 figures, 2 tables; reference added, typos corrected; the model extended, figures changed, title changed, version accepted for publication in Nuclear Physics

Nonthermal dark matter models and signals

Many experiments exploring weakly interacting massive particles (WIMPs) such as direct, indirect and collider searches have been carried out until now. However, a clear signal of a WIMP has not been found yet and it makes us to suspect that WIMPs are questionable as a dark matter candidate. Taking into account this situation, we propose two models in which dark matter relic density is produced by decay of a metastable particle. In the first model, the metastable particle is a feebly interacting massive particle, which is the so-called FIMP produced by freeze-in mechanism in the early universe. In the second model, the decaying particle is thermally produced the same as the usual WIMP. However decay of the particle into dark matter is led by a higher dimensional operator. As a phenomenologically interesting feature of nonthermal dark matter discussed in this paper, a strong sharp gamma-ray emission as an indirect detection signal occurs due to internal bremsstrahlung, although some parameter space has already been ruled out by this process. Moreover combining other experimental and theoretical constraints such as dark matter relic density, big bang nucleosynthesis, collider, gamma-rays and perturbativity of couplings, we discuss the two nonthermal DM models.Comment: 20 pages, 3 figures, 2 tables, version to appear in PR

Higgs Triplet Model with Classically Conformal Invariance

We discuss an extension of the minimal Higgs triplet model with a classically conformal invariance and with a gauged $U(1)_{B-L}$ symmetry. In our scenario, tiny masses of neutrinos are generated by a hybrid contribution from the type-I and type-II seesaw mechanisms. The shape of the Higgs potential at low energies is determined by solving one-loop renormalization group equations for all the scalar quartic couplings with a set of initial values of parameters at the Planck scale. We find a successful set of the parameters in which the $U(1)_{B-L}$ symmetry is radiatively broken via the Coleman-Weinberg mechanism at the ${\cal O}$(10) TeV scale, and the electroweak symmetry breaking is also triggered by the $U(1)_{B-L}$ breaking. Under this configuration, we can predict various low energy observables such as the mass spectrum of extra Higgs bosons, and the mixing angles. Furthermore, using these predicted mass parameters, we obtain upper limits on Yukawa couplings among an isospin triplet Higgs field and lepton doublets from lepton flavor violation data.Comment: References adde

Radiative Seesaw Model with Degenerate Majorana Dark Matter

We study a three loop induced neutrino mass model with exotic vector-like isospin doublet leptons which contain a dark matter candidate. Then we explore lepton flavor violations, and dark matter physics in co-annihilation system. In this paper the nearly degenerate Majorana fermion dark matter can naturally be achieved at the two loop level, while the mass splitting can be larger than ${\cal O}$(200) keV which is required from the constraint of the direct detection search with spin independent inelastic scattering through $Z$ boson portal. As a result a monochromatic photon excess, its threshold energy is greater than ${\cal O}$(200) keV, is predicted in our model that could be measured through indirect detection experiments such as INTEGRAL.Comment: 17 pages, 1 figure, 2 table