No Arabic abstract
We propose a radiative lepton model, in which the charged lepton masses are generated at one-loop level, and the neutrino masses are induced at two-loop level. On the other hand, tau mass is derived at tree level since it is too heavy to generate radiatively. Then we discuss muon anomalous magnetic moment together with the constraint of lepton flavor violation. A large muon magnetic moment is derived due to the vector like charged fermions which are newly added to the standard model. In addition, considering a scalar dark matter in our model, a strong gamma-ray signal is produced by dark matter annihilation via internal bremsstrahlung. We can also obtain the effective neutrino number by the dark radiation of the Goldstone boson coming from the imposed global $U(1)$ 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.
We revisit our previous model proposed in Ref. cite{Okada:2013iba}, in which lepton masses except the tauon mass are generated at the one-loop level in a TeV scale physics. Although in the previous work, rather large Yukawa couplings constants; i.e., greater than about 3, are required to reproduce the muon mass, we do not need to introduce such a large but ${cal O}$(1) couplings. In our model, masses for neutrinos (charged-leptons) are generated by a dimension five effective operator with two isospin triplet (singlet and doublet) scalar fields. Thus, the mass hierarchy between neutrinos and charged-leptons can be naturally described by the difference in the number of vacuum expectation values (VEVs) of the triplet fields which must be much smaller than the VEV of the doublet field due to the constraint from the electroweak rho parameter. Furthermore, the discrepancy in the measured muon anomalous magnetic moment ($g-2$) from the prediction in the standard model are explained by one-loop contributions from vector-like extra charged-leptons which are necessary to obtain the radiative generation of the lepton masses. We study the decay property of the extra leptons by taking into account the masses of muon, neutrinos, muon $g-2$ and dark matter physics. We find that the extra leptons can mainly decay into the mono-muon, dark matter with or without $Z$ bosons in the favored parameter regions.
We study a simple extension of the Zee model, in which a discrete $Z_2$ symmetry imposed in the original model is replaced by a global $U(1)$ symmetry retaining the same particle content. Due to the $U(1)$ symmetry with flavor dependent charge assignments, the lepton sector has an additional source of flavor violating Yukawa interactions with a controllable structure, while the quark sector does not at tree level. We show that current neutrino oscillation data can be explained under constraints from lepton flavor violating decays of charged leptons in a successful charge assignment of the $U(1)$ symmetry. In such scenario, we find a characteristic pattern of lepton flavor violating decays of additional Higgs bosons, which can be a smoking gun signature at collider experiments.
We study a three-loop induced neutrino model with a global $U(1)$ symmetry at TeV scale, in which we naturally accommodate a bosonic dark matter candidate. We discuss the allowed regions of masses and quartic couplings for charged scalar bosons as well as the dark matter mass on the analogy of the original Zee-Babu model, and show the difference between them. We also discuss the possibility of the collider searches, in which future like-sign electron liner collider could be promising.
We study the phenomenology of a keV sterile neutrino in a supersymmetric model with $U(1)_R-$ lepton number in the light of a very recent observation of an X-ray line signal at around 3.5 keV, detected in the X-ray spectra of Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster. This model not only provides a small tree level mass to one of the active neutrinos but also renders a suitable warm dark matter candidate in the form of a sterile neutrino with negligible active-sterile mixing. Light neutrino masses and mixing can be explained once one-loop radiative corrections are taken into account. The scalar sector of this model can accommodate a Higgs boson with a mass of $sim$ 125 GeV. In this model gravitino is the lightest supersymmetric particle (LSP) and we also study the cosmological implications of this light gravitino with mass $sim mathcal O$(GeV).