Eiichi Takasugi

CP violation in Majorana neutrinos

We discuss CP violation in a massive Majorana neutrino system. In general, for the n-Majorana neutrino system (n = number of generations) the number of CP-violation phases in n(n−1)/2 in contrast to the Dirac neutrino system where (n−1)(n−2)/2 phases are present. Therefore, the CP-violation effect appears even in the case of two generations. For neutrino oscillations, however, this number reduces to (n−1)(n−2)/2 due to the special combination of the unitary transformation matrix among the current neutrinos (ν) and mass neutrinos (N).

Lee-Quigg-Thacker bounds for Higgs boson masses in a two doublet model

Abstract Upper bounds for neutral as well as charged Higgs boson masses in a two-doublet model are obtained on the basis of tree unitarity conditions a la Lee, Quigg and Thacker. A wide variety of scattering processes are considered so extensively that our bounds are more restrictive than those obtained previously for neutral Higgs bosons and are also of a new kind for the charged Higgs boson. It is argued that at least one of the Higgs bosons should be lighter than 410 GeV/ c 2 .

DOUBLE BETA DECAY

The double β decay is investigated by the use of the relativistic Coulomb wave function including the finite nuclear size effect. A general form of the V±A interactions is considered. It is shown that the decay rate is enhanced considerably in comparison with the case of the plane wave multiplied by the non-relativistic Fermi factor.

Perturbations of Kerr-de Sitter Black Holes and Heun's Equations

It is well known that the perturbation equations of massless fields for the Kerr-de Sitter geometry can be written in the form of separable equations. The equations have five definite singularities so that the analysis has been expected to be difficult. We show that these equations can be transformed to Heuns equations, for which we are able to use known technique for the analysis of the solutions. We reproduce results known previously for the Kerr geometry and de Sitter geometry in the confluent limits of the Heuns functions. Our analysis applies can be extended to Kerr-Newman-de Sitter geometry for massless fields with spin 0 and 1/2.

Neutrinoless Double Beta Decay With Double Majoron Emission

Abstract In general supersymmetric theories with ultralight superpartners of neutrinos and in specific supersymmetric models with spontaneous violation of R-parity , neutrinoless double beta decay can occur with the emission of two majorons. We discuss the differential electron energy spectrum in this case and possible constraints on the masses of superlattices that arise from the available data on double beta decay.

Neutrino masses and the double β decay

Abstract The double β decay is examined in detail for both the two-nucleon and N ∗ mechanisms. Formulae for the transitions O + → J + are presented. The data on the raio of the 128 Te to 130 Te half-lives by Hennecke et al. suggest that neutrinos are Majorana particles and the estimated average mass is around 30 eV/ c 2 .

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

We study possibility of observing the process

Analytic Solutions of the Teukolsky Equation in Kerr-de Sitter and Kerr-Newman-de Sitter Geometries

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

Can the Neutrinoless Double Beta Decay Take Place in the Case of Dirac Neutrinos

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

Pseudo Dirac Neutrino

10^{-4}