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Yoshio Koide

Publications and source records attributed to Yoshio Koide.

At least 73 records · Page 4Linked to original sources
arXiv2008

O(3) Flavor Symmetry and an Empirical Neutrino Mass Matrix

Based on a new approach to quark and lepton masses, where the mass spectra originate in vacuum expectation values of O(3)-flavor 1+5 (gauge singlet) scalars, a neutrino mass matrix of a new type is speculated. The mass matrix is described in terms of the up-quark and charged lepton masses, and, by assuming a special flavor basis, it can be accommodated to a nearly tribimaximal mixing without explicitly assuming a discrete symmetry. Quark mass relations are also discussed based on the new approach.

hep-ph↗
arXiv2008

U(3)-Flavor Nonet Scalar as an Origin of the Flavor Mass Spectra

According to an idea that the quark and lepton mass spectra originate in a VEV structure of a U(3)-flavor nonet scalar Φ, the mass spectra of the down-quarks and charged leptons are investigated. The U(3) flavor symmetry is spontaneously and completely broken by non-zero and non-degenerated VEVs of $Φ$, without passing any subgroup of U(3). The ratios (m_e+m_μ+m_τ)/(\sqrt{m_e}+\sqrt{m_μ}+\sqrt{m_τ})^2 and \sqrt{m_e m_μm_τ}/(\sqrt{m_e}+\sqrt{m_μ}+\sqrt{m_τ})^3 are investigated based on a toy model.

hep-ph↗
arXiv2008

How to Evade a No-Go Theorem in Flavor Symmetries

A no-go theorem in flavor symmetries is reviewed. The theorem asserts that we cannot bring any flavor symmetry into mass matrix model in which number of Higgs scalars is, at most, one for each sector (e.g. H_u and H_d for up- and down-quark sectors, respectively). Such the strong constraint comes from the SU(2)_L symmetry. Possible three options to evade the theorem are discussed.

hep-ph↗
arXiv2008

F-term Induced Flavor Mass Spectrum

New mechanism of generating flavor mass spectrum is proposed by using an O'Raifeartaigh-type supersymmetry breaking model. A desired bilinear form of fermion mass spectrum is naturally realized through F-components of gauge-singlet (nonet of SU(3) flavor symmetry) superfields, and the suitable charged-lepton mass relation is reproduced. The charged-slepton mass spectrum is non-degenerate in general, and can be even hierarchical (proportional to the charged-lepton masses in the specific case). Flavor changing neutral processes are suppressed since the charged-lepton and slepton (except for right-handed sneutrino) mass matrices are diagonalized simultaneously in the flavor space. The right-handed sneutrinos are light with the similar ratio to the lepton sector ($\tilde{m}_{ν_R}$/$\tilde{m}_e \sim m_ν$/$m_e$).

hep-ph↗
arXiv2007

Neutrino Mixing based on Mass Matrices with a $2 \leftrightarrow 3$ Symmetry

Under the assumption that the $2\leftrightarrow 3$ symmetry is broken only through phases, we give a systematical investigation of possible lepton mass matrix forms without referring to the explicit parameter values. The two types of the $2\leftrightarrow 3$ symmetry are investigated: one is that the left- and right-handed fields $(f_L, f_R)$ obey the symmetry, and another one is that only $f_L$ obeys the symmetry. In latter case, in spite of no $2\leftrightarrow 3$ symmetry in the Majorana mass matrix $M_R$ for $ν_R$, the neutrino seesaw mass matrix still obey the $2\leftrightarrow 3$ symmetry. Possible phenomenologies are discussed.

hep-ph↗
arXiv2007

New Origin of a Bilinear Mass Matrix Form

The charged lepton mass formula can be explained when the masses are propotinal to the squared vacuum expectation values (VEVs) of scalar fields. We introduce U(3) flavor symmetry and its nonet scalar field $Φ$, whose VEV structure plays an essential role for generating the fermion mass spectrum. We can naturally obtain bilinear form of the Yukawa coupling $Y_{ij} \propto \sum_k <Φ_{ik}> <Φ_{kj}>$ without the non-renormalizable interactions, when the flavor symmetry is broken only through the Yukawa coupling and tadpole terms. We also speculate the possible VEV structure of $<Φ>$.

hep-ph↗
arXiv2007

S_4 Flavor Symmetry Embedded into SU(3) and Lepton Masses and Mixing

Based on an assumption that an S_4 flavor symmetry is embedded into SU(3), a lepton mass matrix model is investigated. A Frogatt-Nielsen type model is assumed, and the flavor structures of the masses and mixing are caused by VEVs of SU(2)_L-singlet scalars ϕ_u and ϕ_d which are nonets (8+1) of the SU(3) flavor symmetry, and which are broken into 2+3+3' and 1 of S_4. If we require the invariance under the transformation (ϕ^{(8)},ϕ^{(1)}) \to (-ϕ^{(8)},+ϕ^{(1)}) for the superpotential of the nonet field ϕ^{(8+1)}, the model leads to a beautiful relation for the charged lepton masses. The observed tribimaximal neutrino mixing is understood by assuming two SU(3) singlet right-handed neutrinos ν_R^{(\pm)} and an SU(3) triplet scalar χ.

hep-ph↗
arXiv2007

Broken SU(3) Flavor Symmetry and Tribimaximal Neutrino Mixing

Recent work on a lepton mass matrix model based on an SU(3) flavor symmetry which is broken into S_4 is reviewed. The flavor structures of the masses and mixing are caused by VEVs of SU(2)_L-singlet scalars ϕwhich are nonets ({\bf 8}+{\bf 1}) of the SU(3) flavor symmetry, and which are broken into {\bf 2}+{\bf 3}+{\bf 3}' and {\bf 1} of S_4. If we require the invariance under the transformation (ϕ^{(8)},ϕ^{(1)}) \to (-ϕ^{(8)},+ϕ^{(1)}) for the superpotential of the nonet field ϕ^{(8+1)}, the model leads to a beautiful relation for the charged lepton masses. The observed tribimaximal neutrino mixing is understood by assuming two SU(3) singlet right-handed neutrinos ν_R^{(\pm)} and an SU(3) triplet scalar χ.

hep-ph↗
arXiv2007

A_4 Symmetry and Lepton Masses and Mixing

Stimulated by Ma's idea which explains the tribimaximal neutrino mixing by assuming an A_4 flavor symmetry, a lepton mass matrix model is investigated. A Frogatt-Nielsen type model is assumed, and the flavor structures of the masses and mixing are caused by the VEVs of SU(2)_L-singlet scalars ϕ_i^u and ϕ_i^d (i=1,2,3), which are assigned to {\bf 3} and ({\bf 1}, {\bf 1}',{\bf 1}'') of A_4, respectively.

hep-ph↗
arXiv2007

S_3 Symmetry and Neutrino Masses and Mixings

Based on a universal seesaw mass matrix model with three scalars ϕ_i, and by assuming an S_3 flavor symmetry for the Yukawa interactions, the lepton masses and mixings are investigated systematically. In order to understand the observed neutrino mixing, the charged leptons (e, μ, τ) are regarded as the 3 elements (e_1, e_2, e_3) of S_3, while the neutrino mass-eigenstates are regarded as the irreducible representation (ν_η, ν_σ, ν_π) of S_3, where (ν_π, ν_η) and ν_σare a doublet and a singlet, respectively, which are composed of the 3 elements (ν_1, ν_2, ν_3) of S_3.

hep-ph↗
arXiv2006

Tribimaximal Neutrino Mixing and a Relation Between Neutrino- and Charged Lepton-Mass Spectra

Brannen has recently pointed out that the observed charged lepton masses satisfy the relation m_e +m_μ+m_τ= {2/3} (\sqrt{m_e}+\sqrt{m_μ}+\sqrt{m_τ})^2, while the observed neutrino masses satisfy the relation m_{ν1} +m_{ν2} +m_{ν3} = {2/3} (-\sqrt{m_{ν1}}+\sqrt{m_{ν2}}+\sqrt{m_{ν3}})^2. It is discussed what neutrino Yukawa interaction form is favorable if we take the fact pointed out by Brannen seriously.

hep-ph↗
arXiv2006

Seesaw Mass Matrix Model of Quarks and Leptons with Flavor-Triplet Higgs Scalars

In a seesaw mass matrix model M_f = m_L M_F^{-1} m_R^\dagger with a universal structure of m_L \propto m_R, as the origin of m_L (m_R) for quarks and eptons, flavor-triplet Higgs scalars whose vacuum expectation values v_i are proportional to the square roots of the charged lepton masses m_{ei}, i.e. v_i \propto \sqrt{m_{ei}}, are assumed. Then, it is investigated whether such a model can explain the observed neutrino masses and mixings (and also quark masses and mixings) or not.

hep-ph↗
arXiv2006

Shape of the Unitary Triangle and Phase Conventions of the CKM Matrix

A shape of the unitary triangle versus a CP violating parameter δdepends on the phase conventions of the CKM matrix, because the CP violating parameter δcannot directly be observed, so that it is not rephasing-invariant. In order to seek for a clue to the quark mass matrix structure and the origin of the CP violation, the dependence of the unitary triangle shape on the parameter δis systematically investigated.

hep-ph↗
arXiv2006

Permutation Symmetry S_3 and VEV Structure of Flavor-Triplet Higgs Scalars

A model with flavor-triplet Higgs scalars ϕ_i (i=1,2,3)is investigated under a permutation symmetry S_3 and its symmetry breaking. A possible S_3 breaking form of the Higgs potential whose vacuum expectation values v_i=< ϕ_i> satisfy a relation v_1^2 +v_2^2 +v_3^2 ={2/3}(v_1 +v_2 +v_3)^2 is investigated, because if we suppose a seesaw-like mass matrix model M_e = m M^{-1} m with m_{ij} \propto δ_{ij} v_i and M_{ij} \propto δ_{ij}, such a model can lead to the well-known charged lepton mass relation m_e +m_μ+m_τ= {2/3} (\sqrt{m_e}+\sqrt{m_μ} +\sqrt{m_τ})^2.

hep-ph↗
arXiv2005

Challenge to the Mystery of the Charged Lepton Mass Formula

Why the charged lepton mass formula m_e +m_μ+m_τ= {2/3} (\sqrt{m_e}+\sqrt{m_μ} +\sqrt{m_τ})^2 is mysterious is reviewed, and guiding principles to solve the mystery are presented. According to the principles, an example of such a mass generation mechanism is proposed, where the origin of the mass spectrum is attributed not to the structure of the Yukawa coupling constants, but to a structure of vacuum expectation values of flavor-triplet scalars under Z_4 \times S_3 symmetries.

hep-ph↗
arXiv2005

Quark and Lepton Mass Matrix Structures Suggested by the Observed Unitary Triangle Shape

Under the hypothesis that the CP violating phase parameter δin the CKM matrix V takes own value so that the radius R(δ) of the circle circumscribed about the unitary triangle takes its minimum value, possible phase conventions of the CKM matrix are investigated. We find that two of the 9 phase conventions can give favorable predictions for the observed shape of the unitary triangle. One of the successful two suggests phenomenologically interesting structures of the quark and lepton mass matrices, which lead to |V_{us}|\simeq \sqrt{m_d/m_s}=0.22, |V_{ub}|\simeq \sqrt{m_u/m_t} =0.0036 and |V_{cb}|\simeq \sqrt{m_c/2m_t}=0.043 for the CKM matrix V, and to \sin^2 2θ_{atm}=1, \tan^2 θ_{solar} \simeq |m_{ν1}/m_{ν2}|$ and |U_{13}|\simeq \sqrt{m_e/2 m_τ} for the lepton mixing matrix U under simple requirements for the textures.

hep-ph↗
arXiv2004

Maximal CP Violation Hypothesis and Phase Convention of the CKM Matrix

The maximal CP violation hypothesis depends on the phase convention of the Cabibbo-Kobayashi-Maskawa matrix. A phase convention which leads to successful prediction under the maximal CP violation hypothesis is searched, and thereby, possible structures of the quark mass matrices are speculated.

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