arXiv subjects

Morimitsu Tanimoto

Publications and source records attributed to Morimitsu Tanimoto.

At least 55 records · Page 3Linked to original sources

arXiv2017

Neutrino CP violation and sign of baryon asymmetry in the minimal seesaw model

We discuss the correlation between the CP violating Dirac phase of the lepton mixing matrix and the cosmological baryon asymmetry based on the leptogenesis in the minimal seesaw model with two right-handed Majorana neutrinos and the trimaximal mixing for neutrino flavors. The sign of the CP violating Dirac phase at low energy is fixed by the observed cosmological baryon asymmetry since there is only one phase parameter in the model. According to the recent T2K and NO$ν$A data of the CP violation, the Dirac neutrino mass matrix of our model is fixed only for the normal hierarchy of neutrino masses.

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arXiv2017

Dirac CP phase in the neutrino mixing matrix and the Froggatt-Nielsen mechanism with ${\rm \bf det} \bf [M_ν]=0$

We discuss the Dirac CP violating phase $δ_{CP}$ in the Froggatt-Nielsen model for a neutrino mass matrix $M_ν$ imposing a condition ${\rm det} [M_ν]=0$. This additional condition restricts the CP violating phase $δ_{CP}$ drastically. We find that the phase $δ_{CP}$ is predicted in the region of $\pm (0.4- 2.9)$ radian, which is consistent with the recent T2K and NO$ν$A data. There is a remarkable correlation between $δ_{CP}$ and $\sin^2θ_{23}$. The phase $δ_{CP}$ converges on $\sim \pm π/2$ if $\sin^2θ_{23}$ is larger than $0.5$. Thus, accurate measurements of $\sin^2θ_{23}$ are important for a test of our model. The effective mass $m_{ee}$ for the neutrinoless double beta decay is predicted in the rage of $3.3-4.0$ meV.

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arXiv2016

CP violating phase from minimal texture neutrino mass matrix: Test of the phase relevant to leptogenesis

The model of neutrino mass matrix with minimal texture is now tightly constrained by experiment so that it can yield a prediction for the phase of CP violation. This phase is predicted to lie in the range $δ_{CP}=0.77π- 1.24π$. If neutrino oscillation experiment would find the CP violation phase outside this range, this means that the minimal-texture neutrino mass matrix, the element of which is all real, fails and the neutrino mass matrix must be complex, i.e., the phase must be present that is responsible for leptogenesis.

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arXiv2016

Probing the SUSY with $10$ TeV stop mass in rare decays and CP violation of Kaon

We probe the SUSY at the $10 \ {\rm TeV}$ scale in the rare decays and the CP violation of the kaon. We focus on the processes of $K_L \to π^0 ν{\bar ν}$ and $K^+ \to π^+ ν{\bar ν}$ combined with the CP violating parameters $ε_K$ and $ε_K^\prime/ε_K$. The Z-penguin mediated by the chargino loop cannot enhance $K_L \to π^0 ν{\bar ν}$ and $K^+ \to π^+ ν{\bar ν}$ because the left-right mixing of the stop is constrained by the $125$ GeV Higgs mass. On the other hand, the Z-penguin mediated by the gluino loop can enhance the branching ratios of both $K_L \to π^0 ν{\bar ν}$ and $K^+ \to π^+ ν{\bar ν}$. The former increases up to more than $1.0 \times 10^{-10}$, which is much larger than the SM prediction even if the constraint of $ε_K$ is imposed. It is remarkable that the Z-penguin mediated by the gluino loop can enhance simultaneously $ε^\prime_K/ε_K$ and the branching ratio of $K_L \to π^0 ν{\bar ν}$, which increases up to $1.0 \times 10^{-10}$. We also study the decay rates of $K_L\rightarrow μ^+μ^-$, $B^0\rightarrow μ^+μ^-$ and $B_s\rightarrow μ^+μ^-$, which correlate with the $K_L \to π^0 ν{\bar ν}$ decay through the Z penguin. It is important to examine the $B^0\rightarrow μ^+μ^-$ process since we expect the enough sensitivity of this decay mode to the SUSY at LHCb.

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arXiv2016

Occam's Razor in Lepton Mass Matrices - The Sign of Universe's Baryon Asymmetry -

We discuss the neutrino mass matrix based on the Occam's Razor approach in the framework of the seesaw mechanism. We impose four zeros in the Dirac neutrino mass matrix, which give the minimum number of parameters needed for the observed neutrino masses and lepton mixing angles, while the charged lepton mass matrix and the right-handed Majorana neutrino mass matrix are taken to be real diagonal ones. The low-energy neutrino mass matrix has only seven physical parameters. We show successful predictions for the mixing angle $θ_{13}$ and the CP violating phase $δ_{CP}$ with the normal mass hierarchy of neutrinos by using the experimental data on the neutrino mass squared differences, the mixing angles $θ_{12}$ and $θ_{23}$. The most favored region of $\sinθ_{13}$ is around $0.13\sim 0.15$, which is completely consistent with the observed value. The CP violating phase $δ_{CP}$ is favored to be close to $\pm π/2$. We also discuss the Majorana phases as well as the effective neutrino mass for the neutrinoless double-beta decay $m_{ee}$, which is around $7\sim 8$ meV. It is extremely remarkable that we can perform a "complete experiment" to determine the low-energy neutrino mass matrix, since we have only seven physical parameters in the neutrino mass matrix. In particular, two CP violating phases in the neutrino mass matrix are directly given by two CP violating phases at high energy. Thus, assuming the leptogenesis we can determine the sign of the cosmic baryon in the universe from the low-energy experiments for the neutrino mass matrix.

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arXiv2016

Occam's Razor in Quark Mass Matrices

On the standpoint of Occam's Razor approach, we consider the minimum number of parameters in the quark mass matrices needed for the successful CKM mixing and CP violation. We impose three zeros in the down-quark mass matrix with taking the diagonal up-quark mass matrix to reduce the number of free parameters. The three zeros are maximal zeros in order to have a CP violating phase in the quark mass matrix. Then, there remain six real parameters and one CP violating phase, which is the minimal number to reproduce the observed data of the down-quark masses and the CKM parameters. The twenty textures with three zeros are examined. Among them, the thirteen textures are viable for the down-quark mass matrix. As a representative of these textures, we discuss a texture $M_d^{(1)}$ in details. By using the experimental data on $\sin 2β$, $θ_{13}$ and $θ_{23}$ together with the observed quark masses, the Cabibbo angle is predicted to be close to the experimental data. It is found that this surprising result remains unchanged in all other viable textures. We also investigate the correlations among $|V_{ub}/V_{cb}|$, $\sin 2β$ and $J_{CP}$. For all textures, the maximal value of the ratio $|V_{ub}/V_{cb}|$ is $0.09$, which is smaller than the upper-bound of the experimental data, $0.094$. We hope that this prediction will be tested in future experiments.

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arXiv2015

Testing the minimal $S_4$ model of neutrinos with the Dirac and Majorana phases

We propose two new simple lepton flavor models in the framework of the $S_4$ flavor symmetry. The neutrino mass matrices, which are given by two complex parameters, lead to the inverted mass hierarchy. The charged lepton mass matrix has the 1-2 lepton flavor mixing, which gives the non-vanishing reactor angle $θ_{13}$. These models predict the Dirac phase and the Majorana phases, which are testable in the future experiments. The predicted magnitudes of the effective neutrino mass for the neutrino-less double beta decay are in the regions as $32~\text{meV}\lesssim |m_{ee}|\lesssim 49~\text{meV}$ and $34~\text{meV}\lesssim |m_{ee}|\lesssim 59~\text{meV}$, respectively. These values are close to the expected reaches of the coming experiments. The total sum of the neutrino masses are predicted in both models as $0.0952~\text{eV}\lesssim \sum m_i\lesssim 0.101~\text{eV}$ and $0.150~\text{eV}\lesssim \sum m_i\lesssim 0.160~\text{eV}$, respectively.

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arXiv2015

Sensitivity of High-Scale SUSY in Low Energy Hadronic FCNC

We discuss the sensitivity of the high-scale SUSY at $10$-$1000$ TeV in $B^0$, $B_s$, $K^0$ and $D$ meson systems together with the neutron EDM and the mercury EDM. In order to estimate the contribution of the squark flavor mixing to these FCNCs,we calculate the squark mass spectrum, which is consistent with the recent Higgs discovery. The SUSY contribution in $ε_K$ could be large, around 40% in the region of the SUSY scale $10$-$100$ TeV. The neutron EDM and the mercury EDM are also sensitive to the SUSY contribution induced by the gluino-squark interaction. The predicted EDMs are roughly proportional to $|ε_K^{\rm SUSY}|$. If the SUSY contribution is the level of O(10%) for epsilon_K, the neutron EDM is expected to be discovered in the region of $10^{-28}$-$10^{-26}$ecm. The mercury EDM also gives a strong constraint for the gluino-squark interaction. The SUSY contribution of $ΔM_D$ is also discussed.

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arXiv2015

$K_L \to π^0 ν{\bar ν}$ decay correlating with $ε_K$ in high-scale SUSY

We have studied the contribution of the high-scale SUSY to the K_L to pi^0 nu{bar nu} and K^+ to pi^+ nu{bar nu} processes correlating with the CP violating parameter epsilon_K. Taking account of the recent LHC results for the Higgs discovery and the SUSY searches, we consider the high-scale SUSY at the 10-50 TeV scale in the framework of the non-minimal squark (slepton) flavor mixing. The Z penguin mediated the chargino dominates the SUSY contribution for these decays. At the 10 TeV scale of the SUSY, the chargino contribution can enhance the branching ratio of K_L to pi^0 nu{bar nu} in eight times compared with the SM predictions whereas the predicted branching ratio BR(K^+ to pi^+ nu {bar nu}) increases up to three times of the SM one. The gluino box diagram dominates the SUSY contribution of epsilon_K up to 30%. If the down-squark mixing is neglected compared with the up-squark mixing, the Z penguin mediated the chargino dominates both SUSY contributions of K_L to pi^0 nu {bar nu} and epsilon_K. Then, it is found a correlation between them, but the chargino contribution to epsilon_K is at most 3%. Even if the SUSY scale is 50TeV, the chargino process still enhances the branching ratio of K_L to pi^0 nu {bar nu} from the SM prediction in the factor two, and epsilon_K is deviated from the SM prediction in O(10%) through the gluino box diagram unless the down-squark mixing is suppressed. We also discuss the chargino contribution to K_L to pi^0 e^+e^- process.

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arXiv2015

Linking Leptonic CP violation to Quark Unitarity Triangle

We study the linking between the CP violating phase of the lepton sectors and the unitarity triangle of the B0 meson system. Antusch, King, Malinsky and Spinrath have shown that the quark mass matrices with the negligible 1-3 mixing give an interesting relation between the phase of the quark mixing matrices and CP violating measure phi_2(alpha). This approach is extended by considering the SO(10) GUT including the Pati-Salam symmetry, which links the Yukawa matrices of the quark sector to the one of the lepton sector. We discuss the relation of the CP violating phases between both quark and lepton sectors as well as the mixing angles. Then, the leptonic CP violating phase is predicted in terms of the angle of the unitarity triangle of the B0 meson system. The leptonic CP violating phase deltaPMNS is predicted in the region -74 to -89, which is the consistent with the recent T2K results. Our predicted phase is sensitive to phi_2(alpha) and phi_3(gamma). These predictions will be clearly tested in the future neutrino experiments as well as the Belle-II experiment.

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arXiv2015

Prediction of Leptonic CP Phase in $A_4$ symmetric model

We consider minimal modifications to tribimaximal (TBM) mixing matrix which accommodate non-zero mixing angle $θ_{13}$ and CP violation. We derive four possible forms for the minimal modifications to TBM mixing in a model with $A_4$ flavor symmetry by incorporating symmetry breaking terms appropriately. We show how possible values of the Dirac-type CP phase $δ_D$ can be predicted with regards to two neutrino mixing angles in the standard parametrization of the neutrino mixing matrix. Carrying out numerical analysis based on the recent updated experimental results for neutrino mixing angles, we predict the values of the CP phase for all possible cases. We also confront our predictions of the CP phase with the updated fit.

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arXiv2014

Predicting CP violation in Deviation from Tri-bimaximal mixing of Neutrinos

We study the CP violation in the deviation from the tri-bimaximal mixing (TBM) of neutrinos. We examine non-trivial relations among the mixing angles and the CP violating Dirac phase in the typical four cases of the deviation from the TBM. The first two cases are derived by the additional rotation of the 2-3 or 1-3 generations of neutrinos in the TBM basis. The other two cases are given by the additional rotation of the 1-3 or 1-2 generations of charged leptons with the TBM neutrinos. These four cases predict different relations among three mixing angles and the CP violating Dirac phase. The rotation of the 2-3 generations of neutrinos in the TBM basis predicts $\sin ^2θ_{12}<1/3$, and the CP violating Dirac phase to be $\pm (0.09π\sim 0.76π)$ for NH ($\pm (0.15π\sim 0.73π) \ \text{for IH}$) depending on $\sin ^2θ_{23}$. The rotation of the 1-3 generations of neutrinos in the TBM basis gives $\sin ^2θ_{12}>1/3$. The CP violating Dirac phase is not constrained by the input of the present experimental data. For the case of the 1-3 and 1-2 rotations of charged leptons in the TBM basis, the CP violating Dirac phase is predicted in $\pm(0.35π\sim 0.60π)$ depending on $\sin ^2θ_{12}$ for both NH and IH cases. We also discuss the specific case that $θ_{13}$ is related with the Cabibbo angle $λ$ such as $\sinθ_{13}=λ/\sqrt{2}$, in which the maximal CP violation is preferred. The CP violating Dirac phase can distinguish the lepton flavor mixing patterns at T2K and NO$ν$A experiments in the future.

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arXiv2014

Quark mixing from Delta(6N^2) family symmetry

We consider a direct approach to quark mixing based on the discrete family symmetry Delta (6N^2) in which the Cabibbo angle is determined by a residual Z_2 times Z_2 subgroup to be $|V_{us}|=0.222521$, for $N$ being a multiple of 7. We propose a particular model in which unequal smaller quark mixing angles and CP phases may occur without breaking the residual Z_2 times Z_2 symmetry. We perform a numerical analysis of the model for $N=14$, where small Z_2 times Z_2 breaking effects of order 3% are allowed by model, allowing perfect agreement within the uncertainties of the experimentally determined best fit quark mixing values.

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arXiv2014

Probing the high scale SUSY in CP violations of K, B0 and Bs mesons

We probe the high scale SUSY at 10-50 TeV in the CP violations of K, B0 and Bs mesons. In order to estimate the contribution of the squark flavor mixing to these CP violations, we discuss the squark mass spectrum, which is consistent with the recent Higgs discovery. Taking the universal soft parameters at the SUSY breaking scale, we obtain the squark mass spectrum at 10 TeV and 50 TeV, where the SM emerges. Then, the 6times6 mixing matrix between down-squarks and down-quarks is discussed by input of the experimental data of K, B0 and Bs mesons.It is found that epsilon_K is most sensitive to the high scale SUSY. The SUSY contributions for the time-dependent CP asymmetries S_{ J/psi K_S} and S_{ J/psi phi} are 6-8% at the SUSY scale of 10 TeV. We also discuss the SUSY contribution to the chromo-EDM of the strange quark.

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arXiv2014

Neutrino Mass and Mixing: from Theory to Experiment

The origin of fermion mass hierarchies and mixings is one of the unresolved and most difficult problem in high-energy physics. One possibility to address the flavour problem is by extending the Standard Model to include a family symmetry. In the recent years it has become very popular to use non-Abelian discrete flavour symmetries because of their power in the prediction of the large leptonic mixing angles relevant for neutrino oscillation experiments. Here we give an introduction to the flavour problem and to discrete groups which have been used to attempt a solution for it. We review the current status of models in the light of the recent measurement of the reactor angle and we consider different model building directions taken. The use of the flavons or multi Higgs scalars in model building is discussed as well as the direct vs. indirect approaches. We also focus on the possibility to distinguish experimentally flavour symmetry models by means of mixing sum rules and mass sum rules. In fact, we illustrate in this review the complete path from mathematics, via model building, to experiments, so that any reader interested to start working in the field could use this text as a starting point in order to get a broad overview of the different subject areas.

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arXiv2014

Searching for the squark flavor mixing in CP violations of Bs -> K+ K- and K0bar K0 decays

We study CP violations in the B_s-> K+K- and Bs->K0K0 decays in order to find the contribution of the supersymmetry, which comes from the gluino-squark mediated flavor changing current. We obtain the allowed region of the squark flavor mixing parameters by putting the experimental data, the mass difference Delta M_Bs, the CP violating phase phi_s in Bs to J/psi phi decay and the b to s gamma branching ratio. In addition to these data, we take into account the constraint from the asymmetry of B0->K+pi because the Bs->K+K- decay is related with the B0->K+pi- decay by replacing the spectator s with d. Under these constraints, we predict the magnitudes of the CP violation in the Bs->K+K- and Bs->K0K0 decays. The predicted region of the CP violation C_{K+K-} is strongly cut from the direct CP violation of barB0 to K-pi+, therefore, the deviation from the SM prediction of C_{K+K-} is not found. On the other hand, the CP violation S_{K+K-} is possibly deviated from the SM prediction considerably, in the region of 0.1- 0.5. Since the standard model predictions of C_{K0bar K0} and S_{K0bar K0} are very small, the squark contribution can be detectable in C_{K0bar K0} and S_{K0bar K0}. These magnitudes are expected in the region C_{K0bar K0}=-0.06-0.06 and S_{K0bar K0}=-0.5-0.3. More precise data of these CP violations provide us a crucial test for the gluino-squark mediated flavor changing current.

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arXiv2013

Sensitivity of the squark flavor mixing to the CP violation of K, B0 and Bs mesons

We study the sensitivity of the squark flavor mixing to the CP violating phenomena of $K$, $B^0$ and $B_s$ mesons in the framework of the split-family scenario, where the first and second family squarks are very heavy, ${\cal O}(10)$TeV, on the other hand, the third family squark masses are at ${\cal O}(1)$TeV. In order to constrain the gluino-sbottom-quark mixing parameters, we input the experimental data of the CP violations of $K$, $B^0$, and $B_s$ mesons, that is $ε_K$, $ϕ_d$, and $ϕ_s$. The experimental upper bound of the chromo-EDM of the strange quark is also input. In addition, we take account of the observed values $ΔM_{B^0}$, $ΔM_{B_s}$, the CKM mixing $|V_{ub}|$, and the branching ratio of $b\to sγ$. The allowed region of the mixing parameters are obtained as $|δ_{13}^{dL(dR)}|=0\sim 0.01$ and $|δ_{23}^{dL(dR)}|=0\sim 0.04$. By using these values, the deviations from the SM are estimated in the CP violations of the $B^0$ and $B_s$ decays. The deviation from the SM one is tiny in the CP asymmetries of $B^0\to ϕK_S$ and $B^0\to η'K^0$ due to the chromo-EDM of the strange quark. On the other hand, the CP asymmetries $B_s \to ϕϕ$ and $B_s \to ϕη'$ could be largely deviated from the SM predictions. We also predict the time dependent CP asymmetry of $B^0\to K^0\bar K^0$ and the semi-leptonic CP asymmetries of $B^0 \to μ^-X$ and $B_s \to μ^-X$. We expect those precise measurements at Belle II, which will provide us interesting tests for the squark flavor mixing.

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arXiv2013

SUSY contributions to CP violations in $b\to s$ and $b\to d$ transitions facing on new data

We study the contribution of the gluino-squark mediated flavor changing process for the CP violation in $b\to s$ and $b\to d$ transitions facing on recent experimental data. The mass insertion parameters of squarks are constrained by the branching ratios of $b\to sγ$ and $b\to dγ$ decays. In addition, the time dependent CP asymmetries of $B^0\to ϕK_S$ and $B^0\to η' K^0$ decays severely restrict the allowed region of the mass insertion parameter for the $b\to s$ transition. By using these constraints with squark and gluino masses of 1.5 TeV, we predict the CP asymmetries of $B_s\to ϕϕ$, $B_s\to η'ϕ$, and $B^0\to K^0\bar K^0$ decays, as well as the CP asymmetries in $b\to sγ$ and $b\to dγ$ decays. The CP violation in the $B_s\to ϕϕ$ decay is expected to be large owing to the squark flavor mixing, which will be tested at LHCb soon.

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