http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Radiative seesaw mechanism in a minimal 3-3-1 model
Okada, Hiroshi,Okada, Nobuchika,Orikasa, Yuta American Physical Society 2016 Physical Review D Vol.93 No.7
<P>We study the neutrino sector in a minimal SU(3)(L) x U(1)(X) model, in which its mass is generated at a one-loop level with the charged lepton mass, and hence, there exists a strong correlation between the charged-lepton mass and the neutrino mass. We identify the parameter region of this model to satisfy the current neutrino oscillation data as well as the constraints on lepton flavor violating processes. We also discuss a possibility to explain the muon anomalous magnetic moment.</P>
Nonthermal dark matter models and signals
Okada, Hiroshi,Orikasa, Yuta,Toma, Takashi American Physical Society 2016 Physical Review D Vol.93 No.5
<P>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.</P>
Higgs phenomenology in the minimalSU(3)L×U(1)Xmodel
Okada, Hiroshi,Okada, Nobuchika,Orikasa, Yuta,Yagyu, Kei American Physical Society 2016 Physical Review D Vol.94 No.1
<P>We investigate the phenomenology of a model based on the SU(3)(c) x SU(3)(L) x U(1)(X) gauge theory, the so-called 331 model. In particular, we focus on the Higgs sector of the model which is composed of three SU(3)L triplet Higgs fields and is the minimal form for realizing a phenomenologically acceptable scenario. After the spontaneous symmetry breaking SU(3)(L) x U(1)(X) -> SU(2)(L) x U(1)(Y), our Higgs sector effectively becomes that with two SU(2)(L) doublet scalar fields, in which the first-and the second-generation quarks couple to a different Higgs doublet from that which couples to the third-generation quarks. This structure causes the flavor-changing neutral current mediated by Higgs bosons at the tree level. By taking an alignment limit of the mass matrix for the CP-even Higgs bosons, which is naturally realized in the case with the breaking scale of SU(3)(L) x U(1)(X) much larger than that of SU(2)(L) x U(1)(Y), we can avoid current constraints from flavor experiments such as the B-0-(B) over bar (0) mixing even for the Higgs bosons masses that are O(100) GeV. In this allowed parameter space, we clarify that a characteristic deviation in quark Yukawa couplings of the Standard Model-like Higgs boson is predicted, which has a different pattern from that seen in two Higgs doublet models with a softly broken Z(2) symmetry. We also find that the flavor-violating decay modes of the extra Higgs boson, e.g., H/A -> tc and H-+/- -> ts, can be dominant, and they yield the important signature to distinguish our model from the two Higgs doublet models.</P>