T. Yanagida

Baryogenesis Without Grand Unification

A mechanism is pointed out to generate cosmological baryon number excess without resorting to grand unified theories. The lepton number excess originating from Majorana mass terms may transform into the number excess through the unsuppressed baryon number violation of electroweak processes at high temperatures.

Renormalization-group analysis on the Higgs mass in the softly-broken supersymmetric Standard Model

Abstract We calculate a mass of the lightest Higgs boson in the minimal supersymmetric standard model by solving one-loop renormalization-group equations. In the range mt = 150–200 GeV and for a supersymmetry breaking scale mSUSY = 1–100 TeV the mass mH0 varies from 70 GeV to 190 GeV. A possibility to probe the supersymmetry breaking scale is also discussed.

Horizontal Symmetry and Masses of Neutrinos

A striking and puzzling phenomenon 1s that neutrinos appear nearly massless in contrast to all other leptons and quarks. The left-handed neutrinos may combine with their chiral partners (if they exist) to form Dirac fermions with masses comparable to the usual lepton and quark masses. It has been pointed outu by the present author and independently by Gell-Mann, Ramond and Slansky that this can be avoided if the right-handed neutrinos receive superheavy Maiorana masses. This situation can happenu-s) in some models with continuous horizontal symmetries4) ·5) or grand unified SO (10) models. 6 ) In the SO (10) models, the large Maiorana masses M of right-handed neutrinos can be generated by a 126-plet of Higgs scalar. The value of M would be naturally of order of grand unification mass, 1015 Ge V,*) which leads to undetectably small masses of left-handed neutrinos, ....._,106eV. The smallness of neutrino masses 1s a consequence of the strong breaking of S0(10). On the other hand, in the models with

Lepton-Flavor Violation in the Supersymmetric Standard Model with Seesaw-Induced Neutrino Masses

Abstract We examine the lepton-flavor violation caused by a Yukawa coupling matrix y ν , ij for right-handed neutrinos in the supersymmetric standard model. We stress that decay rates for τ → μγ and μ → eγ are largely enhanced in a parameter region where left-right mixing terms in the slepton mass matrix are substantially large. Especially, these decay rates may reach the range to be accessible to near future experiments even if the SO(10)-like boundary condition on y ν , ij is used. We also discuss how the rates behave if one changes the ansatz on the Yukawa coupling matrix for the right-handed neutrinos.

Nucleon decay in the minimal supersymmetric SU(5) grand unification

We make a detailed analysis on the nucleon decay in the minimal supersymmetric SU(5) grand unified model. We find that a requirement of the unification of three gauge coupling constants leads to a constraint on a mass MHC of the color-triplet Higgs multiplet as 2 × 1013 GeV ⩽ MHC ⩽ 2 × 1017 GeV, taking both weak- and GUT-scale threshold effects into account. Contrary to the results in the previous analyses, the present experimental limits on the nucleon decay turn out to be consistent with the SUSY particles lighter than 1 TeV even without a cancellation between matrix elements contributed from different generations, if one adopts a relatively large value of MHC (⩾ 2 × 1016 GeV). We also show that the Yukawa coupling constant of the color-triplet Higgs multiplet does not necessarily blow up below the gravitational scale (2.4 × 1018 GeV) even with the largest possible value of MHC. We point out that the no-scale model is still viable, though it is strongly constrained.

Hierarchic Chiral Condensate

Abstract Using the Schwinger-Dyson gap equation a chiral condensate is discussed in theories having a slowly varying running-coupling constant. It is shown that if the coupling strength λ remains close to a certain critical value λc up to a large scale Λ, a chiral condensate may occur with the hierarchic nature σ(0)/Λ ≈ exp[ − π/(λ − λ c ) 1 2 ] , σ(0) being the fermion d ynamical mass at zero-momentum. It is pointed out that such a condensate provides a possible solution to the flavor-changing neutral-current problem in the technicolor theory.

Flat potential for inflaton with a discrete R invariance in supergravity

We show that a very flat potential of inflaton required for a sufficient inflation is naturally obtained in

Leptogenesis in supersymmetric standard model with right-handed neutrino

N=1

Quasi goldstone fermions

supergravity by imposing a discrete

Quasi nambu-goldstone fermions

R