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Yoshio Koide

Publications and source records attributed to Yoshio Koide.

117 records · Page 7Linked to original sources
arXiv1996

A Democratic Seesaw Quark Mass Matrix Related to the Charged Lepton Masses

We investigate a seesaw type mass matrix $M_f\simeq m_L M_F^{-1} m_R$ for quarks and leptons, $f$, under the assumptions that the matrices $m_L$ and $m_R$ have common structures for the quarks and leptons, and that the matrix $M_F$ characterizing the heavy fermion sector has the form [(unit matrix)+ (democratic-type matrix)]. We obtain well-satisfied relations for quark masses and mixings related to the charged lepton masses.

hep-ph↗
arXiv1996

Democracy of Families and Neutrino Mass Matrix

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 $M_F$ is given by $M_F=K ({\bf 1} + 3 b_f X)$ ({\bf 1} is a $3\times 3$ unit matrix, $X$ is a democratic-type matrix and $b_f$ is a complex parameter which depends on $f$, neutrino mass spectrum and mixings are discussed. The model can provide an explanation why $m_t \gg m_b$, while $m_u\sim m_d$ by taking $b_u=-1/3$, at which the detarminant of $M_F$ becomes zero. At $b_ν=-1/2$, the model can provide a large $ν_μ$-$ν_τ$ mixing, $\sin^2 2θ_{23}\simeq 1$, with $m_{ν1} \ll m_{ν2} \simeq m_{ν3}$, which is favorable to the atmospheric and solar neutrino data.

hep-ph↗
arXiv1996

U(3)-Family Nonet Higgs Boson and its Phenomenology

In a model where quark and lepton masses and family-mixings are caused not by a variety of Yukawa couplings $y_{ij}$ ($i,j=1,2,3$: family indices) with one vacuum expectation value (VEV) $v=\langleϕ_L^0\rangle_0$, but by a variety of VEV's of a U(3)-family nonet Higgs boson $ϕ_L$, $v_{i}^j=\langleϕ_{L i}^{0j}\rangle_0$, with a single coupling constant, the following problems are investigated: what constraints on the Higgs potential are imposed in order to provide realistic quark and lepton mass spectra and mixings and what constraints on the Higgs boson masses are required in order to suppress unwelcome flavor-changing neutral current effects. Lower bounds of the physical Higgs boson masses of $ϕ_L$ are deduced from the present experimental data and new physics from the present scenario is speculated.

hep-ph↗
arXiv1995

New Physics from U(3)-Family Nonet Higgs Boson Scenario

Being inspired by a phenomenological success of a charged lepton mass formula, a model with U(3)-family nonet Higgs bosons is proposed. Here, the Higgs bosons $ϕ_L$ ($ϕ_R$) couple only between light fermions (quarks and leptons) $f_L$ ($f_R$) and super-heavy vector-like fermions $F_R$ ($F_L$), so that the model leads to a seesaw-type mass matrix $M_f\simeq m_L M_F^{-1} m_R$ for quarks and leptons $f=u,d,ν$ and $e$. Lower bounds of the physical Higgs boson masses are deduced from the present experimental data and possible new physics from the present scenario is speculated.

hep-ph↗
arXiv1994

Electric Dipole Moments of Neutron and Electron in Two-Higgs-Doublet Model with Maximal $CP$ violation

We study the electric dipole moments(EDM) of the neutron and the electron in the two-Higgs-doublet model, in the case that $CP$ symmetry is violated maximally in the neutral Higgs sector. We take account of the Weinberg's operator $O_{3g}=GG\t G$ as well as the operator $O_{qg}=\bar qσ\tilde Gq$ for the neutron, and the Barr-Zee diagrams for the electron. It is found that the predicted neutron EDM could be considerably reduced by the destructive contribution of the two Higgs scalars to get the lower value than the experimental bound. As to the electron EDM, the predicted value is smaller in one order than the experimental one.

hep-ph↗
arXiv1994

Table of Running Quark Mass Values : 1994

Running quark mass values $m_q(μ)$ at some typical energy scales ($μ=1$ GeV, $μ=m_W$, and so on) are reviewed. The values depend considerably on the value of $Λ_{\overline{MS}}$, especially, the value of top quark mass at $μ=1$ GeV does so. The relative ratios of light quark masses ($m_u$, $m_d$ and $m_s$) to heavy quark masses ($m_c$, $m_b$ and $m_t$) are still controversial.

hep-ph↗
arXiv1994

Seesaw-Type Quark and Lepton Mass Matrices and U(3)-Family Nonet Higgs Bosons

A unified mass matrix model of quarks and leptons with a seesaw-type form $M_f=m M_F^{-1} m$ is proposed on the basis of a non-standard Higgs scenario. The matrix $m$ is provided by U(3)-family nonet bosons $ϕ$, and the matrix $M_F$ is a mass matrix of heavy fermions $F_i$ corresponding to the ordinary fermions $f_i=ν_i,e_i,u_i,d_i$ ($i=1,2,3$). It is shown that a Higgs potential of $ϕ$ with a broken U(3)-family symmetry leads to a desirable charged lepton mass formula when $M_E\propto {\bf 1}$. Then, phenomenologically desirable forms of heavy quark mass matrices $M_Q$ ($Q=U,D$) are investigated.

hep-ph↗
arXiv1994

Neutron Electric Dipole Moment in Two Higgs Doublet Model

We study the effect of the "chromo-electric" dipole moment on the electric dipole moment(EDM) of the neutron in the two Higgs doublet model. We systematically investigate the Weinberg's operator $O_{3g}=GG\t G$ and the operator $O_{qg}=\bar qσ\t Gq$, in the cases of $\tan\b\gg 1$, $\tan\b\ll 1$ and $\tan\b\simeq 1$. It is shown that $O_{sg}$ gives the main contribution to the neutron EDM compared to the other operators, and also that the contributions of $O_{ug}$ and $O_{3g}$ cancel out each other. It is pointed out that the inclusion of second lightest neutral Higgs scalar adding to the lightest one is of essential importance to estimate the neutron EDM. The neutron EDM is considerably reduced due to the destructive contribution with each other if the mass difference of the two Higgs scalars is of the order $O(50\G)$.

hep-ph↗