arXiv subjects

Yusuke Shimizu

Publications and source records attributed to Yusuke Shimizu.

65 records · Page 4Linked to original sources

arXiv2011

Breaking Tri-bimaximal Mixing and Large $θ_{13}$

The long baseline neutrino experiment, T2K, and the reactor experiment, Double Chooz will soon present new data. If we expect $\sinθ_{13}$ to be 0.1-0.2, which is close to the present experimental upper bound, we should not persist in the paradigm of the tri-bimaximal mixing. We discuss breaking the tri-bimaximal mixing by adding a simple mass matrix, which could be derived from some non-Abelian discrete symmetries. It is found that $\sinθ_{13}=0.1-0.2$ is expected in our model independent analysis of the generalized mass matrix for the normal or inverted hierarchical neutrino mass spectrum. On the other hand, $\sin^2θ_{23}$ and $\sin^2θ_{12}$ are expected to be not far from 1/2 and 1/3, respectively. As a typical example, we also discuss the $A_4$ flavor model with the 1 and 1' flavons, which break the tri-bimaximal mixing considerably. In this modified version of the Altarelli and Feruglio model, $\sinθ_{13}$ is predicted to be around 0.15 in the case of the normal hierarchical neutrino masses $m_3\gg m_2, m_1$, and 0.2 in the case of the inverted hierarchy $m_3\ll m_2, m_1$. The form of the neutrino mass matrix looks rather interesting --- it is suggestive of other discrete symmetries as well.

hep-ph↗

arXiv2011

Deviations from Tri-Bimaximality and Quark-Lepton Complementarity

We study deviations from tri-bimaximality (TBM) and quark-lepton complementarity (QLC) in a model independent way. The current neutrino experimental data is well approximated by tri-bimaximal generation mixing but the QLC relations are not satisfied with each data of 1$σ$ level. This means that there exist deviations from the complementarity. The same fact for the TBM might be checked in the future neutrino experiments. We discuss such deviations from the TBM and QLC, simultaneously. A new ratio between the deviations is introduced, and some interesting points are presented. We also show predicted correlations among leptonic mixing angles at the points.

hep-ph↗

arXiv2011

Like-sign dimuon asymmetry of B0 meson and LFV in SU(5) SUSY GUT with S4 flavor symmetry

The like-sign dimuon charge asymmetry of the $B$ meson, which was reported in the D$Ø$ Collaboration, is studied in the SU(5) SUSY GUT model with $S_4$ flavor symmetry. Additional CP violating effects from the squark sector are discussed in $B_s-\bar B_s$ mixing process. The predicted like-sign charge asymmetry is in the 2$σ$ range of the combined result of D$Ø$ and CDF measurements. Since the SUSY contributions in the quark sector affect to the lepton sector because of the SU(5) GUT relation, two predictions are given in the leptonic processes: (i) both ${\rm BR}(μ\to e γ)$ and the electron EDM are close to the present upper bound, (ii) the decay ratios of $τ$ decays, $τ\to μγ$ and $τ\to e γ$, are related to each other via the Cabibbo angle $λ_c$: ${\rm BR}(τ\to eγ)/{\rm BR}(τ\to μγ)\sime λ_c^2$. These are testable at future experiments.

hep-ph↗

arXiv2011

Neutrino masses and mixing from S4 flavor twisting

We discuss a neutrino mass model based on the S4 discrete symmetry where the symmetry breaking is triggered by the boundary conditions of the bulk right-handed neutrino in the fifth spacial dimension. While the symmetry restricts bare mass parameters to flavor-diagonal forms, the viable mixing angles emerge from the wave functions of the Kaluza-Klein modes which carry symmetry breaking effect. The magnitudes of the lepton mixing angles, especially the reactor angle is related to the neutrino mass patterns and the model will be tested in future neutrino experiments, e.g., an early (late) discovery of the reactor angle favors the normal (inverted) hierarchy. The size of extra dimension has a connection to the possible mass spectrum; a small (large) volume corresponds to the normal (inverted) mass hierarchy.

hep-ph↗

arXiv2010

Tri-bimaximal Mixing and Cabibbo Angle in S4 Flavor Model with SUSY

We present a flavor model of quarks and leptons with the non-Abelian discrete symmetry $S_4$ in the framework of the SU(5) SUSY GUT. Three generations of $\bar 5$-plets in SU(5) are assigned to ${\bf 3}$ of $S_4$ while the first and second generations of 10-plets in SU(5) are assigned to ${\bf 2}$ of $S_4$, and the third generation of 10-plet is assigned to ${\bf 1}$ of $S_4$. Right-handed neutrinos are also assigned to ${\bf 2}$ for the first and second generations and ${\bf 1}'$ for the third generation. We predict the Cabibbo angle as well as the tri-bimaximal mixing of neutrino flavors. We also predict the non-vanishing $U_{e3}$ of the neutrino flavor mixing due to higher dimensional mass operators. Our predicted CKM mixing angles and the CP violation are consistent with experimental values. We also study SUSY breaking terms in the slepton sector. Our model leads to smaller values of flavor changing neutral currents than the present experimental bounds.

hep-ph↗

arXiv2010

Non-Abelian Discrete Symmetries in Particle Physics

We review pedagogically non-Abelian discrete groups, which play an important role in the particle physics. We show group-theoretical aspects for many concrete groups, such as representations, their tensor products. We explain how to derive, conjugacy classes, characters, representations, and tensor products for these groups (with a finite number). We discussed them explicitly for $S_N$, $A_N$, $T'$, $D_N$, $Q_N$, $Σ(2N^2)$, $Δ(3N^2)$, $T_7$, $Σ(3N^3)$ and $Δ(6N^2)$, which have been applied for model building in the particle physics. We also present typical flavor models by using $A_4$, $S_4$, and $Δ(54)$ groups. Breaking patterns of discrete groups and decompositions of multiplets are important for applications of the non-Abelian discrete symmetry. We discuss these breaking patterns of the non-Abelian discrete group, which are a powerful tool for model buildings. We also review briefly about anomalies of non-Abelian discrete symmetries by using the path integral approach.

hep-th↗

arXiv2009

Delta(54) Flavor Model for Leptons and Sleptons

We have studied $Δ(54)\times Z_2$ flavor model for leptons and sleptons. The tri-bimaximal mixing can be reproduced for arbitrary neutrino masses if vacuum alignments of scalar fields are guaranteed. The deviation from the tri-bimaximal mixing of leptons is predicted. The predicted upper bound for $\sinθ_{13}$ is 0.06. The magnitude of $\sinθ_{23}$ could be deviated from the maximal mixing considerably, but $\sinθ_{12}$ is hardly deviated from the tri-maximal mixing. We have also studied SUSY breaking terms in the slepton sector. Three families of left-handed and right-handed slepton masses are degenerate. Even although flavor symmetry breaking effects are taken into account, our model leads to smaller values of flavor changing neutral currents than the present experimental bounds.

hep-ph↗

arXiv2009

Deviation from tri-bimaximal mixing and flavor symmetry breaking in a seesaw type A4 model

We have studied the contribution of higher order corrections of the flavor symmetry breaking in the $A_4$ seesaw model with the supersymmetry. Taking account of possible higher dimensional mass operators, we predict the deviation from the tri-bimaximal lepton mixing for both normal hierarchy and inverted hierarchy of neutrino masses. We have found that the value of $\sin^2 2θ_{23}$ is larger than 0.96 and the upper bound of $\sin^2θ_{13}$ is 0.01. We have also examined the flavor changing neutral current of leptons from the soft SUSY breaking in slepton masses and A-terms within the framework of supergravity theory. Those magnitudes are enough suppressed to be consistent with experimental constraints.

hep-ph↗

arXiv2009

S4 Flavor Model of Quarks and Leptons

We present an $S_4$ flavor model to unify quarks and leptons in the framework of the SU(5) GUT. Three generations of $\bar 5$-plets in SU(5) are assigned $3_1$ of $S_4$ while the first and the second generations of 10-plets in SU(5) are assigned to be 2 of $S_4$, and the third generation of 10-plet is to be $1_1$ of $S_4$. Right-handed neutrinos are also assigned 2 for the first and second generations and $1_1$ for the third generation, respectively. Taking vacuum alignments of relevant gauge singlet scalars, we predict the quark mixing as well as the tri-bimaximal mixing of neutrino flavors. Especially, the Cabbibo angle is predicted to be $15^{\circ}$ in the limit of the vacuum alignment. We can improve the model to predict observed CKM mixing angles.

hep-ph↗

arXiv2009

Lepton Flavor Model from Delta(54) Symmetry

We present the lepton flavor model with $Δ(54)$, which appears typically in heterotic string models on the $T^2/Z_3$ orbifold. Our model reproduces the tri-bimaximal mixing in the parameter region around degenerate neutrino masses or two massless neutrinos. We predict the deviation from the tri-bimaximal mixing by putting the experimental data of neutrino masses in the normal hierarchy of neutrino masses. The upper bound of $\sin^2θ_{13}$ is 0.01. There is the strong correlation between $θ_{23}$ and $θ_{13}$. Unless $θ_{23}$ is deviated from the maximal mixing considerably, $θ_{13}$ remains to be tiny.

hep-ph↗

arXiv2009

S4 Flavor Symmetry of Quarks and Leptons in SU(5) GUT

We have presented a $S_4$ flavor model to unify quarks and leptons in the framework of the SU(5) GUT. Three generations of $\bar5$-plets in SU(5) are assigned $3_1$ of $S_4$ while the first and the second generations of 10-plets in SU(5) are assigned to be 2 of $S_4$, and the third generation of 10-plet is to be $1_1$ of $S_4$. The right-handed neutrinos are also assigned 2 for the first and second generations and $1_1$ for the third generation, respectively. Taking vacuum alignments of relevant gauge singlet scalars, we predict the quark mixing as well as the tri-bimaximal mixing of neutrino flavors. Especially, the Cabbibo angle is predicted to be $15^{\circ}$ in the limit of the vacuum alignment. We can improve the model to predict observed CKM mixing angles as well as the non-vanishing $U_{e3}$ of the neutrino flavor mixing.

hep-ph↗