Yuji Kajiyama

Universally leptophilic dark matter from non-Abelian discrete symmetry

Abstract The positron anomaly recently reported by the cosmic-ray measurements can be explained by the decaying dark matter scenario, where it decays mainly into leptons with the lifetime of O ( 10 26 ) s . When the dark matter is a fermionic particle, the lifetime of this order is known to be obtained by a dimension 6 operator suppressed by the unification scale ( ∼ 10 16 GeV ) , while such decay operators do not necessarily involve only leptons. In addition, the scenario would be spoiled if there exist lower-dimensional operators inducing the dark matter decay. We show in this Letter that a single non-Abelian discrete symmetry such as A4 is possible to prohibit all such harmful (non-leptonically coupled and lower-dimensional) operators. Moreover, the dark matter decays into charged leptons in a flavor-blind fashion due to the non-Abelian flavor symmetry, which results in perfect agreements not only with the PAMELA data but also with the latest Fermi-LAT data reported very recently. We also discuss some relevance between the discrete symmetry and neutrino physics.

T 7 flavor model in three loop seesaw and Higgs phenomenology

A bstractWe propose a new type of radiative seesaw model in which observed neutrino masses are generated through a three-loop level diagram in combination with tree-level type-II seesaw mechanism in a renormalizable theory. We introduce a Non-abelian flavor symmetry T7 in order to constrain the form of Yukawa interactions and Higgs potential. Although several models based on a Non-abelian flavor symmetry predict the universal coupling constants among the standard model like Higgs boson and charged leptons, which is disfavored by the current LHC data, our model can avoid such a situation. We show a benchmark parameter set that is consistent with the current experimental data, and we discuss multi-muon events as a key collider signature to probe our model.

D(6) Family Symmetry and Cold Dark Matter at LHC

We consider a nonsupersymmetric extension of the standard model with a family symmetry based on

Light dark matter candidate in B – L gauged radiative inverse seesaw

{D}_{6}\ifmmode\times\else\texttimes\fi{}{Z}_{2}\ifmmode\times\else\texttimes\fi{}{Z}_{2}

R-parity violation and non-abelian discrete family symmetry

, where one of

Electron EDM and soft leptogenesis in supersymmetric B − L extension of the standard model

{Z}_{2}

Muon anomalous magnetic moment and lepton flavor violating tau decay in unparticle physics

s is exactly conserved. This

Symmetryless Dark Matter

{Z}_{2}

The SUSY Flavor Problem, Proton Decay and Discrete Family Symmetry

forbids the tree-level neutrino masses and simultaneously ensures the stability of cold dark matter candidates. From the assumption that cold dark matter is fermionic we can single out the

R-Parity Violation and Family Symmetry

{D}_{6}