Anomaly for Model Building

A simple algorithm to calculate the group theory factor entering in anomalies at four and six dimensions for SU(N) and SO(N) groups in terms of the Casimir invariants of their subgroups is presented. Explicit examples of some of the lower dimensional representations of $SU(n), n \leq 5$ and SO(10) groups are presented, which could be used for model building in four and six dimensions.Comment: 9 page

Spontaneous Left-Right Symmetry Breaking in Supersymmetric Models with only Higgs Doublets

We studied the question of parity breaking in a supersymmetric left-right model, in which the left-right symmetry is broken with Higgs doublets (carrying $B-L=\pm 1$). Unlike the left-right symmetric models with triplet Higgs scalars (carrying $B-L=\pm 2$), in this model it is possible to break parity spontaneously by adding a parity odd singlet. We then discussed how neutrino mass of type III seesaw can be invoked in this model by adding extra fermion singlets. We considered simple forms of the mass matrices that are consistent with the unification scheme and demonstrate how they can reproduce the required neutrino mixing matrix. In this model, the baryon asymmetry of the universe is generated via leptogenesis. The required mass scales in the model is then found to be consistent with the gauge coupling unification.Comment: 19 pages, 1 eps figur

About the Mixing and CP Violation in Neutrino System

Suppose the geometrical explaination to the weak CP phase in quark sector is also valid for neutrinos, the mixing and CP violation in neutrino system are discussed. We find a larger $J_{CP}$ than $3\times 10^{-3}$ implys the large-mixing solution for solar neutrino problem. In case of bi-maximal mixing, we predict relative large CP violation with $J_{CP}$ larger than $10^{-3}$ in neutrino system, except the third mixing angle approachs to 0 or $\pi/2$ very closely.Comment: Latex File, 9 pages with 2 EPS figures, Commun. Theor. Phys. in press. A notes and some references are added or renewe

Predictive model for dark matter, dark energy, neutrino masses and leptogenesis at the TeV scale

We propose a new mechanism of TeV scale leptogenesis where the chemical potential of right-handed electron is passed on to the $B-L$ asymmetry of the Universe in the presence of sphalerons. The model has the virtue that the origin of neutrino masses are independent of the scale of leptogenesis. As a result, the model could be extended to explain {\it dark matter, dark energy, neutrino masses and leptogenesis at the TeV scale}. The most attractive feature of this model is that it predicts a few hundred GeV triplet Higgs scalar that can be tested at LHC or ILC.Comment: 5 pages (revtex), double column, 2 eps figures, journal version. To appear in Phys. ReV.

Radiative Left-Right Dirac Neutrino Mass

We consider the conventional left-right gauge extension of the standard model of quarks and leptons without a scalar bidoublet. We study systematically how one-loop radiative Dirac neutrino masses may be obtained. In addition to two well-known cases from almost 30 years ago, we find two new scenarios with verifiable predictions.Comment: 11 pages, 6 figures, text and references adde

Common origin of baryon asymmetry and proton decay

A successful baryogenesis theory requires a baryon-minus-lepton number violation if it works before the electroweak phase transition. The baryon-minus-lepton number violation could also exist in some proton decay modes. We propose a model to show that the cosmological baryon asymmetry and the proton decay could have a common origin. Specifically, we introduce an isotriplet and two isosinglet leptoquark scalars as well as two isotriplet Higgs scalars to the canonical seesaw model. The decays of the Higgs triplets can generate a desired baryon-minus-lepton asymmetry in the leptoquarks. After the Higgs triplets pick up their seesaw-suppressed vacuum expectation values, the leptoquarks with TeV-scale masses can mediate a testable proton decay.Comment: 6 pages, 3 figures. Corrections and improvement

Leptogenesis with Linear, Inverse or Double Seesaw

The left-right symmetric model with doublet and bi-doublet Higgs scalars can accommodate linear, inverse or double seesaw for generating small neutrino masses in the presence of three singlet fermions. If the singlet fermions have small Majorana masses, they can form three pairs of quasi-degenerate Majorana fermions with three right-handed neutrinos. The decays of the quasi-degenerate Majorana fermions can realize the resonant leptogenesis. Alternatively, the right-handed neutrinos can obtain seesaw suppressed Majorana masses if the singlet fermions are very heavy. In this case leptogenesis, with or without resonant effect, is allowed in the decays of the right-handed neutrinos.Comment: 6 pages. Published in Phys. Lett.

Common Origin of Visible and Dark Universe

Dark matter, baryonic matter and dark energy have different properties but contribute comparable energy density to the present Universe. We point out that they may have a common origin. As the dark energy has a scale far lower than all known scales in particle physics but very close to neutrino masses, while the excess matter over antimatter in the baryonic sector is probably related to the neutrino mass-generation, we unify the origin of dark and visible Universe in a variant of seesaw model. In our model (i) the dark matter relic density is a dark matter asymmetry emerged simultaneously with the baryon asymmetry from leptogenesis; (ii) the dark energy is due to a pseudo-Nambu-Goldstone-Boson associated with the neutrino mass-generation.Comment: 7 pages, 1 figur