arXiv subjects

Hideyuki Sawanaka

Publications and source records attributed to Hideyuki Sawanaka.

12 recordsLinked to original sources

arXiv2010

Cascade Hierarchy in SUSY SU(5) GUT

We study cascade hierarchy in supersymmetric SU(5) grand unified theory. The neutrino Dirac mass matrix of the cascade form can lead to the tri-bimaximal generation mixing at the leading order in the seesaw mechanism while the down quark mass matrix of a hybrid cascade form naturally gives the CKM structure. We embed such experimentally favored mass textures into supersymmetric SU(5) GUT, which gives a relation between the down quark and charged lepton mass matrices. Related phenomenologies, such as lepton flavor violating processes and leptogenesis, are also investigated in addition to lepton mixing angles.

hep-ph↗

arXiv2009

Probing neutrino masses and tri-bimaximality with lepton flavor violation searches

We examine relation between neutrino oscillation parameters and prediction of lepton flavor violation, in light of deviations from tri-bimaximal mixing. Our study shows that upcoming experimental searches for lepton flavor violation process can provide useful implications for neutrino mass spectrum and mixing angles. With simple structure of heavy right-handed neutrino and supersymmetry breaking sectors, the discovery of tau \to mu gamma decay determines neutrino mass hierarchy if large (order 0.1) reactor angle is established.

hep-ph↗

arXiv2007

New Approach to Texture-zeros with S_3 symmetry - Flavor Symmetry and Vacuum Aligned Mass Textures -

A texture-zeros is an approach to reduce the number of free parameters in Yukawa couplings and it is one of the most attractive ones. In our paper, we discuss the origin of zero-structure in texture-zeros by S_3 flavor symmetry approach. Some of electroweak doublet Higgs fields have vanishing vacuum expectation value(VEV) which leads to vanishing elements in quark and lepton mass matrices. Then, the structure of supersymmetric scalar potential is analyzed and Higgs fields have non-trivial S_3 charges. As a prediction of our paper, a lower bound of a MNS matrix element, U_{e3} \geq 0.04, is obtained. The suppression of flavor-changing neutral currents(FCNC) mediated by the Higgs fields is discussed and lower bounds of the Higgs masses are derived.

hep-ph↗

arXiv2006

Flavor Symmetry and Vacuum Aligned Mass Textures

The mass matrix forms of quarks and leptons are discussed in theory with permutation flavor symmetry. The structure of scalar potential is analyzed in case that electroweak doublet Higgs fields have non-trivial flavor symmetry charges. We find that realistic forms of mass matrices are obtained dynamically in the vacuum of the theory, where some of Higgs bosons have vanishing expectation values which lead to vanishing elements in quark and lepton mass matrices. Mass textures are realized in the true vacuum and their positions are controlled by flavor symmetry. An interesting point is that, due to the flavor group structure, the up and down quark mass matrices are automatically made different in the vacuum, which lead to non-vanishing generation mixing. It is also discussed that flavor symmetry is needed to be broken in order not to have too light scalars. The lower bounds of Higgs masses are derived from the experimental data of flavor-changing rare processes such as the neutral K meson mixing.

hep-ph↗

arXiv2006

$S_3$ Higgs Potential and Texture-zeros in Supersymmetric Standard Model

The mass matrix forms of quarks and leptons are discussed in theory with permutation flavor symmetry. The structure of scalar potential is analyzed in case that electroweak doublet Higgs fields have non-trivial flavor symmetry charges. We find that realistic forms of mass matrices are obtained dynamically in the vacuum of the theory, where some of Higgs bosons have vanishing expectation values which lead to vanishing elements in quark and lepton mass matrices. An interesting point is that, due to the flavor group structure, the up and down quark mass matrices are automatically made different in the vacuum, which lead to non-vanishing generation mixing. It is also discussed that flavor symmetry is needed to be broken in order not to have too light scalars.

hep-ph↗

arXiv2006

Rotational Symmetry and A Light Mode in Two-Dimensional Staggered Fermions

To obtain a light mode in two-dimensional staggered fermions, we introduce four new local operators keeping the rotational invariance for a staggered Dirac operator. To split masses of tastes, three cases are considered. The mass matrix and the propagator for free theories are analyzed. We find that one of three cases is a good candidate for taking a single mode by the mass splitting. In the case, it is possible that a heavy mode obtains infinite mass on even sites or odd sites.

hep-lat↗

arXiv2006

Quark Masses and Mixing with A4 Family Symmetry

The successful A4 family symmetry for leptons is applied to quarks, motivated by the quark-lepton assignments of SU(5). Realistic quark masses and mixing angles are obtained, in good agreement with data. In particular, we find a strong correlation between |V_{ub}| and the CP phase beta, thus allowing for a decisive future test of this model.

hep-ph↗

arXiv2005

Mu-tau antisymmetry and neutrino mass matrices

Using the seesaw mechanism and a discrete symmetry, we construct a class of models for the neutrino mass matrix where the inverse of that matrix is the sum of a mu-tau antisymmetric background and a perturbation. We consider various possibilities for that perturbation. The simplest possible perturbations lead to four-parameter neutrino mass matrices which are unable to fit the experimental data. More complicated perturbations give rise to viable six-parameter mass matrices; we present detailed predictions of each of them.

hep-ph↗

arXiv2005

Hybrid Textures of Neutrinos

We present numerical and comprehensive analyses of the sixty hybrid textures of neutrinos, which have an equality of matrix elements and one zero. These textures are possibly derived from the discrete symmetry. Only six textures among sixty ones are excluded by the present experimental data. Since there are many textures which give similar predictions, the textures are classified based on the numerical results. The neutrinoless double beta decay is also examined in these textures. Our results suggest that there remain still rich structures of the neutrino mass matrix in the phenomenological point of view.

hep-ph↗

arXiv2005

Non-vanishing $U_{e3}$ and $\cos{2 θ_{23}}$ from a broken $Z_2$ symmetry

It is shown that the neutrino mass matrices in the flavour basis yielding a vanishing $U_{e3}$ are characterized by invariance under a class of $Z_2$ symmetries. A specific $Z_2$ in this class also leads to a maximal atmospheric mixing angle $θ_{23}$. The breaking of that $Z_2$ can be parameterized by two dimensionless quantities, $\e$ and $\e'$; the effects of $\e, \e' \neq 0$ are studied perturbatively and numerically. The induced value of $\ue3$ strongly depends on the neutrino mass hierarchy. We find that $\ue3$ is less than 0.07 for a normal mass hierarchy, even when $\e, \e' \sim 30 %$. For an inverted mass hierarchy $\ue3$ tends to be around 0.1 but can be as large as 0.17. In the case of quasi-degenerate neutrinos, $\ue3$ could be close to its experimental upper bound 0.2. In contrast, $| \cos{2θ_{23}} |$ can always reach its experimental upper bound 0.28. We propose a specific model, based on electroweak radiative corrections in the MSSM, for $\e$ and $\e'$. In that model, both $\ue3$ and $| \cos{2 θ_{23}} |$, could be close to their respective experimental upper bounds if neutrinos are quasi-degenerate.

hep-ph↗

arXiv2004

Genuine Symmetry of Staggered Fermion

We present a new formulation of the staggered fermion on the D-dimensional lattice based on the SO(2D) Clifford algebra, which is naturally present in the action. The action of the massless staggered fermion is invariant under the discrete rotation and the SO(2D) chiral and other discrete transformations. From transformation properties of the fermion, we find two local meson operators (one scalar and one pseudoscalar) in addition to two standard meson operators.

hep-lat↗

arXiv2001

Towards the Super Yang-Mills Theory on the Lattice

We present an entirely new approach towards a realization of the supersymmetric Yang-Mills theory on the lattice. The action consists of the staggered fermion and the plaquette variables distributed in the Euclidean space with a particular pattern. The system is shown to have fermionic symmetries relating the fermion and the link variables.

hep-lat↗