Related papers: Natural fourth generation of leptons
I suggest a practical particle model as an extension to the standard model. The model has a TeV scale $U(1)_{B-L}$ symmetry and it contains the fourth generation fermions with the TeV scale masses, in which including a cold dark matter…
It is possible that there are additional vector-like generations where the quarks have mass terms that do not originate from weak symmetry breaking, but the leptons only get mass through weak symmetry breaking. We discuss the impact that…
We study the distribution of lepton pairs from the second lightest neutralino decay \tchi^0_2\to\tchi^0_1 l^+l^-. This decay mode is important to measure the mass difference between \tchi^0_2 and the lightest neutralino \tchi^0_1, which…
Leptogenesis induced by the oscillations of GeV-scale neutrinos provides a minimal and testable explanation of the baryon asymmetry of the Universe. In this work we extend previous studies invoking only two heavy neutrinos to the case of…
Flavor physics, like cosmology, is likely in need of new basic ideas; the puzzles of elementary particle mass hierarchies and in particular the e-mu-tau and neutrino ones still remain mysteries. In this paper a new idea of dynamical…
A fourth generation of quarks, if it exist, may provide sufficient CP violation for the baryon asymmetry of the Universe. We estimate the neutron electric dipole moment in the presence of a fourth generation, and find it would be dominated…
In this paper, we put constraints on neutrino properties such as mass $m_{\nu}$ and degeneracy parameters $\xi_i$ from WMAP5 data and light element abundances by using a Markov chain Monte Carlo (MCMC) approach. In order to take…
We show that large leptonic mixing occurs most naturally in the framework of the Sandard Model just by adding a fourth generation. One can then construct a small $Z_4$ discrete symmetry, instead of the large $S_{4L}\times S_{4R}$, which…
A possible extension of the Standard Model to include lepton number as local gauge symmetry is investigated. In such a model, anomalies are canceled by two extra fermions doublet. After leptonic gauge symmetry spontaneously broken, three…
We analyze the power of the Tevatron dataset to exclude or discover fourth generation neutrinos. In a general framework, one can have mixed left- and right-handed neutrinos, with Dirac and Majorana neutrinos as extreme cases. We demonstrate…
Naturally small neutrino masses can arise in some grand unified models. The mechanism of neutrino mass generation in these models typically requires the existence of neutral heavy leptons. We study the low-energy phenomenology of these new…
The possibility of additional quarks and leptons beyond the three generations already established is discussed. The make-up of this Report is (I) Introduction: the motivations for believing that the present litany of elementary fermions is…
The possible existence of bulk singlet neutrinos in the scenario with large compactified dimensions and low string scale $M_*$ has important consequences for low-energy observables. We demonstrate that intergenerational mass splitting and…
Precise measurements of the lepton properties provide stringent tests of the Standard Model structure and accurate determinations of its parameters. We overview the present status of a few selected topics: lepton universality, QCD tests and…
We study resonant leptogenesis at the electroweak phase transition in the singlet Majoron model with right-handed neutrinos. We consider a scenario, where the SM gauge group and the lepton number break down spontaneously during a…
We generalize the scalar triplet neutrino mass model, the type II seesaw. Requiring fine-tuning and arbitrarily small parameters to be absent leads to dynamical lepton number breaking at the electroweak scale and a rich LHC phenomenology. A…
The seesaw model of heavy and light Majorana neutrinos and its low-energy effective theory are studied, when the number of heavy neutrinos is equal to or less than the number of light lepton generations. We establish a general relationship…
We have investigated the possibility of direct tests of little Higgs models incorporating triplet Higgs neutrino mass mechanism at LHC experiments. We have performed Monte Carlo studies of Drell-Yan pair production of doubly charged Higgs…
Seesaw models with a slightly broken lepton number symmetry can explain small neutrino masses, and allow for low-scale leptogenesis. We make a thorough analysis of leptogenesis within the simplest model with two right-handed (RH) neutrinos…
The model of neutrino mass matrix with minimal texture is now tightly constrained by experiment so that it can yield a prediction for the phase of CP violation. This phase is predicted to lie in the range $\delta_{CP}=0.77\pi - 1.24\pi$. If…