arXiv subjects

Koichi Matsuda

Publications and source records attributed to Koichi Matsuda.

17 recordsLinked to original sources

arXiv2008

Quark Mixing from Mass Matrix Model with Flavor 2 (\leftrightarrow) 3 Symmetry

We consider an universal mass matrix model which has a seesaw-invariant structure with the most general texture based on flavor 2 (\leftrightarrow) 3 symmetry common to all quarks and leptons. The CKM quark mixing matrix of the model is analyzed. It is shown that the model is consistent with all the experimental data of quark mixings by tuning free parameters of the model. We also show that the values of parameters of the present model consistent with the experimental data are not far from the ones of the mass matrix model with a vanishing (1,1) element.

hep-ph↗

arXiv2008

Constraint on the heavy sterile neutrino mixing angles in the SO(10) model with double see-saw mechanism

Constraints on the heavy sterile neutrino mixing angles are studied in the framework of a minimal supersymmetric ${\rm SO}(10)$ model with {\it double see-saw mechanism}. A new singlet matter in addition to the right-handed neutrinos is introduced to realize the double see-saw mechanism. The minimal ${\rm SO}(10)$ model gives an unambiguous Dirac neutrino mass matrix, which enables us to predict the masses and the mixing angles in the enlarged $9 \times 9$ neutrino mass matrix. Mixing angles between the light Majorana neutrinos and the heavy sterile neutrinos are shown to be within the LEP experimental bound on all ranges of the Majorana phases.

hep-ph↗

arXiv2007

New physics effect on the top-Yukawa coupling at ILC

Measurement of the top-Yukawa coupling is important to understand the fermion mass generation mechanism and dynamics of electroweak symmetry breaking. We discuss the top quark anomalous couplings which can be described by higher dimensional operators. We investigate the process $e^-e^+ \to W^-W^+ν\barν\to t \bar t ν\barν$ to study the contribution of the anomalous top-Higgs coupling to the cross section. The effect of the dimension-six top-Higgs interaction on the cross section can be a few hundred percent greater than the SM prediction. Such a large effect can be measured at the International Linear Collider.

hep-ph↗

arXiv2007

CP violation due to multi Froggatt-Nielsen fields

We study how to incorporate CP violation in the Froggatt--Nielsen (FN) mechanism. To this end, we introduce non-renormalizable interactions with a flavor democratic structure to the fermion mass generation sector. It is found that at least two iso-singlet scalar fields with imposed a discrete symmetry are necessary to generate CP violation due to the appearance of the relative phase between their vacuum expectation values. In the simplest model, ratios of quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) matrix including the CP violating phase are determined by the CKM element |V_{us}| and the ratio of two vacuum expectation values R=|R|e^{i*alpha} (a magnitude and a phase). It is demonstrated how the angles phi_i (i=1--3) of the unitarity triangle and the CKM off-diagonal elements |V_{ub}| and |V_{cb}| are predicted as a function of |V_{us}|, |R| and α. Although the predicted value of the CP violating phase does not agree with the experimental data within the simplest model, the basic idea of our scenario would be promising to construct a more realistic model of flavor and CP violation.

hep-ph↗

arXiv2007

Zero Texture Model and SO(10) GUT

We study the bridge between the phenomenological mass matrix model and SO(10) GUT. Namely, we consider the four zero texture model in the framework of the renormalizable SO(10) GUT model. This unification gives more stringent constraints than the case where only either model is considered. However, we can obtain good fitting by expanding the minimal SO(10) GUT to include 120 in addition to 10 and \bar 126 in Yukawa coupling and by considering both type-I and type-II seesaw mechanisms.

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arXiv2006

Can four-zero-texture mass matrix model reproduce the observed quark and lepton mixing angles and CP violating phases?

We reconsider an universal mass matrix model which has a seesaw-invariant structure with four-zero texture common to all quarks and leptons. The CKM quark and MNS lepton mixing matrices of the model are analyzed analytically.We show that the model can be consistent with all the experimental data of neutrino oscillation and quark mixings by tuning free parameters of the model. It is also shown that the model predicts a relatively large value for (1,3) element of the MNS lepton mixing matrix, |(U_{MNS})_{13}|^2 \simeq 2.6 \times 10^{-2}. Using the seesaw mechanism, we also discuss the conditions for the components of the Dirac and the right-handed Majorana neutrino mass matrices which lead to the neutrino mass matrix consistent with the experimental data.

hep-ph↗

arXiv2005

Broken Flavor 2 <-> 3 Symmetry and phenomenological approach for universal quark and lepton mass matrices

A phenomenological approach for the universal mass matrix model with a broken flavor 2 <-> 3 symmetry is explored by introducing the 2 <-> 3 antisymmetric parts of mass matrices for quarks and charged leptons . We present explicit texture components of the matrices, which are consistent with all the neutrino oscillation experiments and quark mixing data. The mass matrices have a common structure for quarks and leptons, while the large lepton mixings and the small quark mixings are derived with no fine tuning due to the difference of the phase factors. The model predicts a value, 2.4 x 10^{-3}, for the lepton mixing matrix element square |U_{13}|^2, and also predict =(0.89-1.4) x 10^{-4} eV for the averaged neutrino mass which appears in the neutrinoless double beta decay.

hep-ph↗

arXiv2005

Enhancement of lepton flavor violation in a model with bi-maximal mixing at the grand unification scale

We study phenomenological predictions in the scenario with the quasi-degenerate relation among neutrino Dirac masses, m_D1 simeq m_D2 < m_D3, assuming the bi-maximal mixing at the grand unification scale in supersymmetric standard models with right-handed neutrinos. A sufficient lepton number asymmetry can be produced for successful leptogenesis. The lepton flavor violating process mu to e gamma can be enhanced due to the Majorana phase, so that it can be detectable at forthcoming experiments. The processes tau to e gamma and tau to mu gamma are suppressed because of the structure of neutrino Dirac masses, and their branching ratios are smaller than that of mu to e gamma.

hep-ph↗

arXiv2005

Phase effects from the general neutrino Yukawa matrix on lepton flavor violation

We examine contributions from Majorana phases to lepton flavor violating processes in the framework of the minimal supersymmetric standard model with heavy right-handed neutrinos. All phases in the complex neutrino Yukawa matrix are taken into account in our study. We find that in the scenario with universal soft-breaking terms sizable phase effects can appear on the lepton flavor violating processes such as $μ\to e γ$, $τ\to e γ$, and $τ\to μγ$. In particular, the branching ratio of $μ\to e γ$ can be considerably enhanced due to the Majorana phases, so that it can be much greater than that of $τ\to μγ$.

hep-ph↗

arXiv2005

Large Lepton Mixing and Nonsymmetric Mass Matrices with Flavor 2 <-> 3 Symmetry

We analyze the lepton sector of a recently proposed nonsymmetric mass matrix model. Our model gives a unified description of quark and lepton with the same texture form based on an extended flavor $2 \leftrightarrow 3$ symmetry with a phase. By investigating possible types of assignment for masses, we find that the model can lead to large lepton mixings which are consistent with experimental values. We also find that the model predicts a very small value, $1.3\times10^{-10}$, for the lepton mixing matrix element square $|U_{13}|^2$. The CP violating phases in the lepton mixing matrix and a suppression of the averaged neutrino mass in the neutrinoless double beta decay are also predicted.

hep-ph↗

arXiv2005

Neutrino Oscillations in a Supersymmetric SO(10) Model with Type-III See-Saw Mechanism

The neutrino oscillations are studied in the framework of the minimal supersymmetric SO(10) model with Type-III see-saw mechanism by additionally introducing a number of SO(10) singlet neutrinos. The light Majorana neutrino mass matrix is given by a combination of those of the singlet neutrinos and the $SU(2)_L$ active neutrinos. The minimal SO(10) model gives an unambiguous Dirac neutrino mass matrix, which enables us to predict the masses and the other parameters for the singlet neutrinos. These predicted masses take the values accessible and testable by near future collider experiments under the reasonable assumptions. More comprehensive calculations on these parameters are also given.

hep-ph↗

arXiv2005

Prediction for Quark Mixing from Universal Quark and Lepton Mass Matrices with Flavor 2 <-> 3 Symmetry

We propose a mass matrix model that gives a unified description of quark and lepton with the same texture form based on a flavor 2 <-> 3 symmetry. The model is in contrast with the conventional picture that the mass matrix forms in the quark sector will take somewhat different structures from those in the lepton sector. By investigating possible types of assignment for masses, we find that our quark mass matrices can lead to small CKM quark mixings which are consistent with experimental values. We also find some phase-parameter-independent relations among CKM quark mixing matrix elements.

hep-ph↗

arXiv2004

Lepton Flavor Violation in the Higgs Boson Decay at a Linear Collider

We study possibility of observing the process $h^{0} \to τ^{\pm} μ^{\mp}$ at a linear collider. The branching ratio is constrained to be of the order of $10^{-4}$ by the $τ^{-} \to μ^{-} η$ result. Supersymmetric standard models can reproduce such amount of the branching ratio by taking a specific parameter set. The Higgsstrahlung process $e^{+}e^{-} \to Zh^{0}$ is preferable because of its simple kinematic structure, then, the signal process is $e^{+} e^{-} \to Z h^{0} \to Z τ^{\pm} μ^{\mp}$. The most serious background comes from the process, $e^{+} e^{-} \to Zh^{0} \to Zτ^{\pm} τ^{\mp} \to τ^{\pm} μ^{\mp} ν\barν$. We estimate the significance of the signal, taking into account the background reduction.

hep-ph↗

arXiv2004

Lepton Mixing Matrix Element U_{13} and New Assignments of Universal Texture for Quark and Lepton Mass Matrices

We reanalyze the mass matrix model of quarks and leptons that gives a unified description of quark and lepton mass matrices with the same texture form. By investigating possible types of assignment for the texture components of the lepton mass matrix, we find that a different assignment for neutrinos than for charged leptons can also lead to consistent values of the MNSP lepton mixing matrix. We also find that the predicted value for the lepton mixing matrix element $U_{13}$ of the model depends on the assignment. A proper assignment will be discriminated by future experimental data for $U_{13}$.

hep-ph↗

arXiv2003

Assignments of Universal Texture Components for Quark and Lepton Mass Matrices

We reanalyze the mass matrices model of quarks and leptons which gives a unified description of quark and lepton mass matrices with the same texture form. By investigating possible types of the assignment for the texture's components of this mass matrix form, we find that a different assignment for up-quarks from one for down-quarks can lead to consistent values of CKM mixing matrix. This finding overcomes a weak point of the previous analysis of the model. We also obtain some relations among the CKM mixing matrix parameters, which are independent of evolution effects.

hep-ph↗

arXiv2003

Universal Texture of Quark and Lepton Mass Matrices

Against the conventional picture that the mass matrix forms in the quark sectors will take somewhat different structures from those in the lepton sectors, a possibility that all the mass matrices of quarks and leptons have the same form as in the neutrinos is investigated. For the lepton sectors, the model leads to a nearly bimaximal mixing with the prediction |U_{e3}|^2=m_e/2m_μ=0.0024 and \tan^2θ_{sol} \simeq m_{ν1}/m_{ν2}, and so on. For the quark sectors, it can lead to reasonable values of the CKM mixing matrix and masses: |V_{us}|\simeq \sqrt{m_d/m_s}, |V_{ub}| \simeq |V_{cb}|\sqrt{m_u/m_c}, |V_{td}| \simeq |V_{cb}|\cdot |V_{us}|, and so on.

hep-ph↗

arXiv2002

Universal Texture of Quark and Lepton Mass Matrices and a Discrete Symmetry Z_3

Recent neutrino data have been favourable to a nearly bimaximal mixing, which suggests a simple form of the neutrino mass matrix. Stimulated by this matrix form, a possibility that all the mass matrices of quarks and leptons have the same form as in the neutrinos is investigated. The mass matrix form is constrained by a discrete symmetry Z_3 and a permutation symmetry S_2. The model, of course, leads to a nearly bimaximal mixing for the lepton sectors, while, for the quark sectors, it can lead to reasonable values of the CKM mixing matrix and masses.

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