arXiv subjects

Yoshio Koide

Publications and source records attributed to Yoshio Koide.

At least 109 records · Page 6Linked to original sources

arXiv2000

Democratic Universal Seesaw Model with Three Light Sterile Neutrinos

Based on the "democratic" universal seesaw model, where mass matrices $M_f$ of quarks and leptons f_i (f=u,d,ν,e; i=1,2,3) are given by a seesaw form M_f\simeq -m_L M_F^{-1} m_R, and m_L and m_R are universal for all the fermion sectors, and the mass matrices M_F of hypothetical heavy fermions F_i have a democratic structure, a possible neutrino mass matrix is investigated. In the model, there are three sterile neutrinos ν_{iR} which mix with the active neutrinos ν_{iL} with θ\sim 10^{-2} and which are harmless for constraint from the bib bang nucleosynthesis. The atmospheric, solar and LSND neutrino data are explained by the mixings ν_{μL} \leftrightarrowν_{τL}, ν_{eL}\leftrightarrow ν_{eR} and ν_{eL}\leftrightarrow ν_{μL}, respectively. The model predicts that Δm^2_{solar}/Δm^2_{atm} \simeq (R^2-1) m_e/\sqrt{m_μm_τ} [R=m(ν_{iR})/m(ν_{iL}) (i=1,2,3)] with \sin^{2}2θ_{atm}\simeq 1 and Δm_{LSND}^2/Δm^2_{atm} \simeq (1/4)\sqrt{m_μ/m_e} with \sin^2 2θ_{LSND} \simeq 4m_e/m_μ.

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arXiv2000

Quark and Lepton Mass Matrices with a Cyclic Permutation Invariant Form

As an attempt to give an unified description of quark and lepton mass matrices M_f, the following mass matrix form is proposed: the form of the mass matrices are invariant under a cyclic permutation (f_1 \to f_2, f_2 \to f_3, f_3 \to f_1) among the fermions f_i. The model naturally leads to the maximal mixing between ν_μand ν_τ, and with an additional ansatz, it leads to the well-satisfied relations |V_{us}| \simeq \sqrt{m_d/m_s} and |V_{cb}| \simeq \sqrt{m_d/m_b}.

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arXiv1999

SO(10) \times SO(10) Universal Seesaw Model and its Intermediate Mass Scales

On the basis of the universal seesaw mass matrix model, which is a promising model of the unified description of the quark and lepton mass matrices, the behaviors of the gauge coupling constants and intermediate energy scales in the SO(10)_L \times SO(10)_R model are investigated related to the neutrino mass generation scenarios. The non-SUSY model cannot give favorable values of the intermediate energy scales to explain the smallness of the neutrino masses, while the SUSY model can give the plausible values if the number n_ϕof the weak doublet Higgs scalars is n_ϕ\geq 3.

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arXiv1999

Universal Seesaw Mass Matrix Model with an S_3 Symmetry

Stimulated by the phenomenological success of the universal seesaw mass matrix model, where the mass terms for quarks and leptons f_i (i=1,2,3) and hypothetical super-heavy fermions F_i are given by \bar{f}_L m_L F_R +\bar{F}_L m_R f_R + \bar{F}_L M_F F_R + h.c. and the form of M_F is democratic on the bases on which m_L and m_R are diagonal, the following model is discussed: The mass terms M_F are invariant under the permutation symmetry S_3, and the mass terms m_L and m_R are generated by breaking the S_3 symmetry spontaneously. The model leads to an interesting relation for the charged lepton masses.

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arXiv1999

Universal Seesaw Mass Matrix Model and SO(10)\times SO(10) Unification

On the universal seesaw mass matrix model, which is a promising model of the unified description of the quark and lepton mass matrices, the behaviors of the gauge coupling constants and intermediate energy scales in the SO(10)_L\times SO(10)_R model are investigated related to the neutrino mass generation scenarios. The unification of the gauge coupling constants in the framework of the non-SUSY model is possible if the SO(10) symmetry is broken via Pati-Salam type symmetries.

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arXiv1998

Universal Seesaw Mass Matrix Model with Three Light Pseudo-Dirac Neutrinos

A universal seesaw mass matrix model, which gives successful description of quark mass matrix in terms of lepton masses, yields three "sterile" neutrinos ν^s_{i}, which compose pseudo-Dirac neutrinos ν_{i\pm}^{ps}\simeq (ν_{i} \pm ν^s_{i})/\sqrt{2} together with the active neutrinos ν_{i} (i=e,μ,τ). The solar and atmospheric neutrino data are explained by the mixings ν_{e}\leftrightarrow ν^s_{e} and ν_μ\leftrightarrow ν^s_μ, respectively. In spite of such observations of the large mixing \sin^2 2θ\simeq 1 in the disappearance experiments, effective mixing parameters \sin^2 2θ^{αβ} in appearance experiments ν_α\toν_β(α, β= e, μ, τ) are highly suppressed.

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arXiv1998

Universal Seesaw Mass Matrix Model and Neutrino Phenomenology

Stimulated by the recent development of the ``universal seesaw mass matrix model", an application of the model to the neutrino mass matrix is investigated: For the charged lepton and down-quark sectors, the model explains the smallness of their masses $m_f$ by the conventional seesaw mechanism M_f\simeq m_L M_F^{-1}m_R (M_F is a mass matrix of hypothetical heavy fermions F). On the other hand, the observed fact m_t\sim Λ_L=O(m_L) (electroweak scale Λ_L=174 GeV) seems to reject the applying of the seesaw mechanism to the up-quark sector. However, recently, it has been found that, by taking det M_F=0 for the up-quark sector F=U, we can understand the question of why only top quark has a mass of the order of Λ_L without the sesaw-suppression factor O(m_R)/O(M_F). For neutrino sector, the mass matrix M_νis given by M_ν\simeq m_L M_F^{-1} m_L^T (F=N), so that the masses m_νare suppressed by a factor O(m_L)/O(m_R) compared with the conventional quark and charged lepton masses. The model can naturally lead to a large mixing \sin^2 2θ\simeq 1. Also another model is investigated within the framework of the universal seesaw model: the model leads to three sets of the almost degenerate two Majorana neutrinos which are large mixing states between the left-handed neutrinos ν_{Li} and SU(2)_L\timesSU(2)_R singlet neutrinos N_{1i} (i=e,μ,τ), so that the model can give a simultaneous explanation of the atmospheric and solar neutrino data.

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arXiv1998

Coupling Constants Evolution in a Universal Seesaw Mass Matrix Model

Stimulated by a universal seesaw mass matrix model which can successfully give quark masses and CKM matrix elements in terms of charged lepton masses, the evolution of the seesaw mass matrices is investigated. Especially, an investigation is made as to whether the evolution can constrain the necessary intermediate scales in these types of models and its viability.

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arXiv1998

New Aspects on a Seesaw Mass Matrix Model

Recent development of the universal seesaw mass matrix model is reviewed. The model was proposed in order to explain why quark and lepton masses are so small compared with the electroweak scale Λ_L =<ϕ_L^0>=174 GeV. However, the recently observed top-quark mass m_t\simeq 180 GeV seems to make an objection against the seesaw mass picture. For this problem, it has recently pointed out that the seesaw mass matrix model is rather favorable to the fact m_t\sim Λ_L if we consider the model with det M_F=0 for up-quark sector, where M_F is a 3 x 3 mass matrix of hypothetical heavy fermions F. The model can give a natural explanation why only top-quark acquire the mass of the order of Λ_L. The model with det M_U=0 offers abundant new physics to us (e.g., the fourth up-quark t', FCNC, and so on).

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arXiv1997

Updated Estimate of Running Quark Masses

Stimulated by recent development of the calculation methods of the running quark masses $m_q(μ)$ and renewal of the input data, for the purpose of making a standard table of $m_q(μ)$ for convenience of particle physicists, the values of $m_q(μ)$ at various energy scales $μ$ ($μ= 1$ GeV, $μ= m_c$, $μ=m_b$, $μ=m_t$ and so on), especially at $μ= m_Z$, are systematically evaluated by using the mass renormalization equations and by taking into consideration a matching condition at the quark threshold.

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arXiv1997

Neutrino Masses and Mixings in a Universal Seesaw Mass Matrix Model

Neutrino masses and mixings are investigated on the basis of a universal seesaw mass matrix model, in which quark (except for top) and charged lepton mass matrices M_f and neutrino mass matrix M_νare given by M_f \simeq m_L M_F^{-1} m_R and M_ν\simeq m_L M_F^{-1} m_L^T (F=N), respectively. For a simple model which can successfully describe quark masses and mixings, we find that the observed neutrino data (except for the solar neutrino data) are favor to the intermediate mass scales O(m_R) = 10^{11} GeV and O(M_F)= 10^{13} GeV together with O(m_L)= 10^2 GeV. In spite of the largesse of O(m_R), the observed top quark mass can be consistently understood from the would-be seesaw mass matrix with these mass scales.

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arXiv1997

Updated Running Quark Mass Values

The running quark masses at various energy scales are evaluated by using the mass renormalization equations systematically. Also, those at energy scales higher than m_Z are evaluated by using the evolution equations of Yukawa coupling constants for the standard model with a single Higgs boson.

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arXiv1997

Abnormal Structure of Fermion Mixings in a Seesaw Quark Mass Matrix Model

It is pointed out that in a seesaw quark mass matrix model which yields a singular enhancement of the top-quark mass, the right-handed fermion-mixing matrix U_R^u for the up-quark sector has a peculiar structure in contrast to the left-handed one U_L^u. As an example of the explicit structures of U_L^u and U_R^u, a case in which the heavy fermion mass matrix M_F is given by a form [(unit matrix)+(rank-one matrix)] is investigated. As a consequence, one finds observable signatures at projected high energy accelerators like the production of a fourth heavy quark family.

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arXiv1997

NNI-Form Quark Mass Matrix Expressed by the Observable Quantities

It is pointed out that the phase convention of the CKM matrix V affects texture analysis of the quark mass matrices (M_u, M_d) when we try to describe (M_u, M_d) by the observable quantities (quark masses and CKM matrix parameters) only. This is demonstrated for a case of the non-Hermitian Fritzsch-type mass matrix (tilde{M}_u, tilde{M}_d), which is a general expression of quark mass matrix (M_u, M_d) and is described by twelve parameters. We find that we can always choose a phase convention of V which yields tilde{M}_{u32} = 0, so that the remaining ten parameters in (tilde{M}_u, tilde{M}_d) can completely be expressed by the ten observable quantities.

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arXiv1997

Democratic Seesaw Mass Matrix Model and New Physics

A seesaw mass matrix model is reviewed as a unification model of quark and lepton mass matrices. The model can understand why top-quark mass m_t is so singularly enhanced compared with other quark masses, especially, why m_t >> m_b in contrast to m_u = O(m_d), and why only top-quark mass is of the order of the electroweak scale Lambda_W, i.e., m_t = O(Lambda_W). The model predicts the fourth up-quark t' with a mass m_{t'}= O(m_{W_R}), and an abnormal structure of the right-handed up-quark mixing matrix U_R^u. Possible new physics is discussed.

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arXiv1997

Flavor-Changing Neutral Currents Induced by the Democratic Seesaw Mass Matrix

Flavor-changing neutral currents (FCNC) are studied on the basis of a ``democratic seesa'' mass matrix model, which yields a singular enhancement of the top-quark mass m_t and can give reasonable quark masses and CKM matrix elements. The most exciting aspect of the model is that the structure of the $6 \times 6$ right-handed fermion mixing matrix in the up-quark sector, $U^R_u$, shows an abnormal structure in contrast to that of $U^L_u$. This causes characteristic effects on the right-handed FCNC concerned with top quark. A single top-quark production at future $e^+ e^-$ colliders, $e^+ + e^- \to Z_R \to t + \overline{c}$ ($\overline{t}+c$), is discussed.

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arXiv1996

Analytical Expressions of Masses and Mixings in a Democratic Seesaw Mass Matrix Model

On the basis of a seesaw-type mass matrix model $M_f\simeq m_L M_F^{-1} m_R$ for quarks and leptons $f$, analytical expressions of the masses and mixings of the fermions $f$ are investigated. Here, the matrices $m_L$ and $m_R$ are common to all $f$ (up- and down-; quarks and leptons), and the matrix $M_F$ characterizing the heavy fermion sector has the form [(unit matrix)+ (democratic-type matrix)]. An application to the quark sectors is discussed.

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arXiv1996

Neutrino Mixing in a Democratic-Seesaw-Mass-Matrix Model

On the basis of a seesaw-type mass matrix model for quarks and leptons, $M_f \simeq m_L M_F^{-1} m_R$, where $m_L\propto m_R$ are universal for $f=u,d,ν$ and $e$ (up-quark-, down-quark-, neutrino- and charged lepton-sectors), and $M_F$ has a form [(unit matrix)+(democratic-type matrix)], neutrino masses and mixings are investigated. It is tried to understand a large $ν_μ$-$ν_τ$ mixing, i.e., $\sin^2 2θ_{23}\sim 1$, with $m_{ν1} \ll m_{ν2} \sim m_{ν3}$, which has been suggested by the atmospheric neutrino data.

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