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Yoshio Koide

Publications and source records attributed to Yoshio Koide.

At least 55 records · Page 3Linked to original sources
arXiv2011

Unified description of quark and lepton mixing matrices based on a Yukawaon model

Based on a supersymmetric Yukawaon model with O(3) family symmetry, possible forms of quark and lepton mixing matrices are systematically investigated under a condition that the up-quark mass matrix form leads to the observed nearly tribimaximal mixing in the lepton sector. Although the previous model could not provide a good fitting of the observed quark mixing, the present model can give a reasonably good fitting not for lepton mixing but also the quark mixing by using a different origin of the $CP$ violation from one in the previous model.

hep-ph↗
arXiv2010

Tests of a Family Gauge Symmetry Model at 10^3 TeV Scale

Based on a specific model with U(3) family gauge symmetry at $10^3$ TeV scale, we show its experimental signatures to search for. Since the gauge symmetry is introduced with a special purpose, its gauge coupling constant and gauge boson mass spectrum are not free. The current structure in this model leads to family number violations via exchange of extra gauge bosons. We investigate present constraints from flavor changing processes and discuss visible signatures at LHC and lepton colliders.

hep-ph↗
arXiv2010

New U(3) Family Gauge Symmetry and Muonium into Antimuonium Conversion

According to Sumino's idea, a family U(3) gauge symmetry is assumed. SU(2)$_L$ doublet fields $q_L$ and $\ell_L$ are assigned to {\bf 3} of U(3), while singlets $u_R$, $d_R$, $e_R$ and $ν_R$ are assigned to {\bf 3$^*$} of U(3). Then, current-current interactions with flavor number violations of $|ΔN_{f}|=2$ ($N_{f}$ is an individual family number) appear via the family gauge boson exchanges. Since the gauge symmetry model has inevitably been brought by Sumino with a specific purpose, the gauge coupling constants g_f and the gauge boson mass spectrum m_{fij}\equiv m(A_i^j) are not free parameters. We estimate m_{f11} \sim 10^{0-1} TeV and m_{f12} \sim 10^{1-2} TeV. As a possible signature of such the flavor number violating interactions, muonium into antimuonium conversion is discussed together with a rare kaon decay K^+ \rightarrow π^+ + μ^- +e^+.

hep-ph↗
arXiv2010

Charged Lepton Mass Spectrum and a Scalar Potential Model

Stimulated by a recent work by Sumino, on the basis of a model in which effective Yukawa coupling constants are described by vacuum expectation values of a scalar $Φ$ with $3\times 3$ components, a possible form of the scalar potential $V(Φ)$ which can well describe the observed charged lepton mass spectrum is investigated without referring to a specific flavor symmetry model. A general relation among eigenvalues of <Φ> is derived without referring to an explicit form of $V(Φ)$.

hep-ph↗
arXiv2010

Quark Mass Matrix Model for Neutrino Mixing

For the purpose of deriving the observed nearly tribimaximal neutrino mixing, a possible quark mass matrix model is investigated based on a yukawaon model. The neutrino mass matrix is related to the up-quark mass matrix. Five observable quantities (2 up-quark mass ratios and 3 neutrino mixing parameters) are excellently fitted by two parameters (one parameter in the up-quark mass matrix and another one in the neutrino mass matrix). Also, the CKM mixing parameters and down-quark mass ratios are given under the other 2 parameters.

hep-ph↗
arXiv2010

Yukawaon Approach to the Sumino Relation for Charged Lepton Masses

On the basis of a supersymmetric yukawaon model, Sumino's relation for charged lepton masses is re-derived. A relation between values of $K(μ) \equiv (m_e +m_μ+ m_τ)/(\sqrt{m_e} + \sqrt{m_μ} + \sqrt{m_τ})^2$ and $κ(μ) \equiv \sqrt{m_e m_μm_τ}/ (\sqrt{m_e} + \sqrt{m_μ}+ \sqrt{m_τ})^3$ is investigated without using a relation $K=2/3$. Predicted value of $κ(μ)$ is compared with the observed value of $κ(μ)$, and it is concluded that the value $ξ(μ)\equiv (3/2)K(μ) -1$ is of the order of $10^{-3}$ or less.

hep-ph↗
arXiv2010

Yukawaon model and unified description of quark and lepton mass matrices

In the so-called yukawaon model, where effective Yukawa coupling constants Y_f^{eff} (f=e,ν,u,d) are given by vacuum expectation values of gauge singlet scalars (yukawaons) Y_f with 3\times 3 flavor components, it is tried to give a unified description of quark and lepton mass matrices. Especially, without assuming any discrete symmetry in the lepton sector, nearly tribimaximal mixing is derived by assumed a simple up-quark mass matrix form.

hep-ph↗
arXiv2009

Can Massless and Light Yukawaons be Harmless?

In the so-called yukawaon model, where the effective Yukawa coupling constants Y_f^{eff} (f=e,ν,u,d) are given by vacuum expectation values (VEVs) of gauge singlet scalars (yukawaons) Y_f with 3\times 3 components, i.e. Y_f^{eff}= y_f < Y_f>/Λ, massless (and light) scalars appear because a global flavor symmetry is assumed. In order to demonstrate whether such massless scalars in the yukawaon model are harmless or not, yukawaon masses are explicitly estimated, as an example, in the charged lepton sector.

hep-ph↗
arXiv2009

Charged Lepton Mass Spectrum and Supersymmetric Yukawaon Model

On the basis of the so-called supersymmetric yukawaon model, it is investigated what form of the superpotential W can lead to the observed charged lepton mass spectrum. A simple form of W can speculate reasonable values of K(μ)=(m_e +m_μ+ m_τ)/(\sqrt{m_e} + \sqrt{m_μ} + \sqrt{m_τ})^2 and κ(μ)=\sqrt{m_e m_μm_τ}/ (\sqrt{m_e} + \sqrt{m_μ}+ \sqrt{m_τ})^3 at an energy scale μ=Λ.

hep-ph↗
arXiv2009

Yukawaon Model in the Quark Sector and Nearly Tribimaximal Neutrino Mixing

For the purpose of deriving the observed nearly tribimaximal neutrino mixing, a possible yukawaon model in the quark sector is investigated. Five observable quantities (2 up-quark mass ratios and 3 neutrino mixing parameters \sin^2 2θ_{atm}, \tan^2θ_{solar} and |U_{13}|) are excellently fitted by two parameters (one in the up-quark sector and another one in the right-handed Majorana neutrino sector).

hep-ph↗
arXiv2009

Maximal CP Violation Hypothesis and a Lepton Mixing Matrix

Maximal CP violation hypothesis is applied to a simple lepton mixing matrix form U=V_{CKM}^\dagger U_{TB}, which has recently been speculated under an ansatz that U becomes an exact tribimaximal mixing U_{TB} in a limit of the quark mixing matrix V_{CKM} \to {\bf 1}. The prediction \tan^2 θ_{12} =1/2 in the case of the exact tribimaximal mixing U=U_{TB} is onsiderably spoiled in the speculated mixing U=V_{CKM}^\dagger U_{TB}. However, the application of the hypothesis to the lepton sector can again recover the spoiled value to \tan^2 θ_{12} \simeq 1/2 if the original Kobayashi-Maskawa phase convention for V_{CKM} is adopted.

hep-ph↗
arXiv2009

Charged Lepton Mass Relations in a Supersymmetric Yukawaon Model

According to an idea that effective Yukawa coupling constants Y_f^{eff} are given vacuum expectation values < Y_f> of fields ("Yukawaons") Y_f as Y_f^{eff}=y_f < Y_f>/Λ, a possible superpotential form in the charged lepton sector under a U(3) [or O(3)] flavor symmetry is investigated. It is found that a specific form of the superpotential can lead to an empirical charged lepton mass relation without any adjustable parameters.

hep-ph↗
arXiv2008

Phenomenological Meaning of a Neutrino Mass Matrix Related to Up-Quark Masses

Recently, a curious neutrino mass matrix has been proposed: it is related to up-quark masses, and it can excellently give a nearly tribimaxial mixing. It is pointed out that, in order to obtain such successful results, three phenomenological relations among masses and CKM parameters must be simultaneously satisfied. This suggests that there must be a specific flavor-basis in which down-quark and charged lepton mass matrices are simultaneously diagonalized.

hep-ph↗
arXiv2008

Empirical Neutrino Mass Matrix Related to Up-Quark Masses

Based on an approach to quark and lepton masses, where the mass spectra originate in vacuum expectation values of U(3) flavor nonet (gauge singlet) scalars, neutrino masses and mixing are investigated. As an offshoot of this approach, it is found that an empirical neutrino mass matrix which is described in terms of the up-quark and charged lepton masses can accommodate to a nearly tribimaximal mixing.

hep-ph↗
arXiv2008

Testable Deviation from Exact Tribimaximal Mixing

A simple relation U_{MNS}=V_{CKM}^\dagger U_{TB} between the lepton and quark mixing matrices (U_{MNS} and V_{CKM}) is speculated under an ansatz that U_{MNS} becomes an exact tribimaximal mixing U_{TB} in a limit V_{CKM}={\bf 1}. By using the observed CKM mixing parameters, possible values of neutrino oscillation parameters are estimated: \sin^2 θ_{13}=0.024-0.028, \sin^2 2θ_{23}=0.94-0.95 and \tan^2 θ_{12}=0.24-1.00 depending on phase conventions of U_{TB}. Those values are testable soon by precision measurements in neutrino oscillation experiments.

hep-ph↗
arXiv2008

Neutrino Mass Hierarchies in a Mass Matrix Form Versus its Inverse Form

A neutrino mass matrix model M_νwith M_ν^T =M_νand a model with its inverse matrix form \widetilde{M}_ν= m_0^2 (M_ν^*)^{-1} can be diagonalized by the same mixing matrix U_ν. It is investigated whether a scenario which provides a matrix model M_νwith normal mass hierarchy can also give a model with an inverted mass hierarchy by considering a model with an inverse form of M_ν.

hep-ph↗