Partial Mass Degenerated Model and Spontaneous CP Violation in the Leptonic Sector

We have investigated a flavour model [1] which inspired by small squared-mass difference measured in solar neutrino oscillation experiments and observability in neutrinoless double beta decay experiments. In our model, the $1^{\rm st.}$ and $2^{\rm nd.}$ generations of fermions have a common mass at the leading order. Such limit may be a good starting point from the points of view of understanding the mixing patterns and mass spectra. In this limit, the mass matrices are respected an $O (2)$ symmetry on flavor space of the first two generations. For simplicity, we propose a model for lepton sector based on the $D_N$ group which is a discrete subgroup of $O (2)$. We show that our model can reproduce the experimental data without hierarchical couplings except for 5 \mathchar`- 10% tuning partially for the large neutrino mixing. Further, we show a novel relation between the tiny electron mass and the relatively large $\theta_{13}^{\rm PMNS}$ via CP violation by the complex vacuum expectation values of the extra scalar fields.Comment: 5 pages, 3 figures, Proceeding for HPNP 2013, Toyama, Feb. 201

Partial mass-degeneracy and spontaneous CP violation in the lepton sector

Inspired by the small mass-squared difference measured in the solar neutrino oscillation experiments and by the testability, we suggest that a limit of the partial mass degeneracy, in which masses of the first two generation fermions are degenerate, may be a good starting point for understanding the observed fermion mass spectra and mixing patterns. The limit indicates the existence of a two-dimensional rotation symmetry, such as $O(2)$, $D_N$ and so on, in flavor space of the first two generations. We propose simple models for the lepton sector based on $D_N$ and show that the models can successfully reproduce the experimental data without imposing unnatural hierarchies among dimensionless couplings, although at least $10\%$ tuning is necessary in order to explain a large atmospheric mixing. It is especially found that the $Z_2$ subgroup of the $D_N$ symmetry plays an important role in understanding the smallness of the electron mass and $\theta_{13}^{\rm PMNS}$. We also discuss testability of the models by the future neutrinoless-double-beta-decay experiments and cosmological observations.Comment: 21pages, 1figure, correspond to published versio

Flavour Mixing of Neutrinos and Baryon Asymmetry of the Universe

We investigate baryogenesis in the $\nu$MSM, which is the Minimal Standard Model (MSM) extended by three right-handed neutrinos with Majorana masses smaller than the weak scale. In this model the baryon asymmetry of the universe (BAU) is generated via flavour oscillation between right-handed neutrinos. We consider the case when BAU is solely originated from the CP violation in the mixing matrix of active neutrinos. We perform analytical and numerical estimations of the yield of BAU, and show how BAU depends on mixing angles and CP violating phases. It is found that the asymmetry in the inverted hierarchy for neutrino masses receives a suppression factor of about 4% comparing with the normal hierarchy case. It is, however, pointed out that, when $\theta_{13}=0$ and $\theta_{23} = \pi/4$, baryogenesis in the normal hierarchy becomes ineffective, and hence the inverted hierarchy case becomes significant to account for the present BAU.Comment: 15 pages, 7 figure

Higgs inflation and Higgs portal dark matter with right-handed neutrinos

We investigate the Higgs inflation and the Higgs portal dark matter with the right-handed neutrino. The dark matter and the right-handed neutrino in the Higgs inflation play important roles in explaining the recent experimental results of the Higgs and top masses, and the cosmic microwave background by BICEP2 at the same time. This inflation model predicts $805~{\rm GeV} \lesssim m_{\rm DM} \lesssim1220~{\rm GeV}$ for the DM mass, $1.05 \times10^{14}~{\rm GeV} \lesssim M_R \lesssim 2.04 \times10^{14}~{\rm GeV}$ for the right-handed neutrino mass, and $8.42 \lesssim \xi \lesssim 12.4$ for the non-minimal coupling within $m_H=125.6 \pm 0.35~{\rm GeV}$ for the Higgs and $M_t=173.34 \pm 0.76~{\rm GeV}$ for the top masses.Comment: 10 pages, 1 figure, v2: corrected typos in beta functions and small error in calculations, conclusions unchanged, v3: matches to the published versio

Gauge coupling unification in a classically scale invariant model

There are a lot of works within a class of classically scale invariant model, which is motivated by solving the gauge hierarchy problem. In this context, the Higgs mass vanishes at the UV scale due to the classically scale invariance, and is generated via the Coleman-Weinberg mechanism. Since the mass generation should occur not so far from the electroweak scale, we extend the standard model only around the TeV scale. We construct a model which can achieve the gauge coupling unification at the UV scale. In the same way, the model can realize the vacuum stability, smallness of active neutrino masses, baryon asymmetry of the universe, and dark matter relic abundance. The model predicts the existence vector-like fermions charged under $SU(3)_C$ with masses lower than $1\,{\rm TeV}$, and the SM singlet Majorana dark matter with mass lower than $2.6\,{\rm TeV}$.Comment: 20 pages, 6 figures, published version in JHE

Vanishing Higgs potential at the Planck scale in a singlet extension of the standard model

We discuss the realization of a vanishing effective Higgs potential at the Planck scale, which is required by the multiple-point criticality principle (MPCP), in the standard model with singlet scalar dark matter and a right-handed neutrino. We find the scalar dark matter and the right-handed neutrino play crucial roles for realization of the MPCP, where a neutrino Yukawa becomes effective above the Majorana mass of the right-handed neutrino. Once the top mass is fixed, the MPCP at the (reduced) Planck scale and the suitable dark matter relic abundance determine the dark matter mass, $m_S$, and the Majorana mass of the right-handed neutrino, $M_R$, as $8.5~(8.0)\times10^2~{\rm GeV}\leq m_S\leq1.4~(1.2)\times10^3~{\rm GeV}$ and $6.3~(5.5)\times10^{13}~{\rm GeV}\leq M_R\leq1.6~(1.2)\times10^{14}~{\rm GeV}$ within current experimental values of the Higgs and top masses. This scenario is consistent with current dark matter direct search experiments, and will be checked by future experiments such as LUX with further exposure and/or the XENON1T.Comment: 11 pages, 14 figures, published versio

Naturalness and lepton number/flavor violation in inverse seesaw models

We introduce three right-handed neutrinos and three sterile neutrinos, and consider an inverse seesaw mechanism for neutrino mass generation. From naturalness point of view, their Majorana masses should be small, while it induces a large neutrino Yukawa coupling. Then, a neutrinoless double beta decay rate can be enhanced, and a sizable Higgs mass correction is inevitable. We find that the enhancement rate can be more than ten times compared with a standard prediction from light neutrino contribution alone, and an analytic form of heavy neutrino contributions to the Higgs mass correction. In addition, we numerically analyze the model, and find almost all parameter space of the model can be complementarily searched by future experiments of neutrinoless double beta decay and $\mu \to e$ conversion.Comment: 19 pages, 6 figures: version accepted for publication in JHE

Detecting Current Outliers: Continuous Outlier Detection over Time-Series Data Streams

Database and Expert Systems Applications 19th International Conference DEXA 2008 Turin Italy September 1-5 2008.journal articl