Tetsuo Shindou

Probing gravitino dark matter with PAMELA and Fermi

We analyze the cosmic-ray signatures of decaying gravitino dark matter in a model independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both, the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribution of decaying gravitinos to the gamma-ray spectrum, in particular a line at an energy below 300 GeV. Future measurements of the gamma-ray flux will provide important constraints on possible signatures of decaying gravitino dark matter at the LHC.

An R-parity conserving radiative neutrino mass model without right-handed neutrinos

The model proposed by A. Zee (1986) and K. S. Babu (1988) is a simple radiative seesaw model, in which tiny neutrino masses are generated at the two-loop level. We investigate a supersymmetric extension of the Zee-Babu model under R-parity conservation. The lightest superpartner particle can then be a dark matter candidate. We find that the neutrino data can be reproduced with satisfying current data from lepton flavour violation even in the scenario where not all the superpartner particles are heavy. Phenomenology at the Large Hadron Collider is also discussed.

Search for lepton flavor violation in the Higgs boson decay at a linear collider

We study possibility of observing the process

Exploring the neutrino mass matrix at the M R scale

h^{0} \to \tau^{\pm} \mu^{\mp}

Exploring flavor structure of supersymmetry breaking from rare B decays and the unitarity triangle

at a linear collider. The branching ratio is constrained to be of the order of

The renormalization group effect to the bi-maximal mixing

10^{-4}

Superparticle mass window from leptogenesis and decaying gravitino dark matter

by the

Radiative neutrino mass, dark matter and electroweak baryogenesis from the supersymmetric gauge theory with confinement

\tau^{-} \to \mu^{-} \eta

Exploring flavor structure of supersymmetry breaking at

result. Supersymmetric standard models can reproduce such amount of the branching ratio by taking a specific parameter set. The Higgsstrahlung process

B

e^{+}e^{-} \to Zh^{0}