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Y. Takanishi

Publications and source records attributed to Y. Takanishi.

At least 19 recordsLinked to original sources

Neutrinoless Double Beta Decay and H^{\pm\pm}\to {l'}^\pm l^\pm Decays in the Higgs Triplet Model

The connection between the neutrinoless double beta ((ββ)_{0 ν}-) decay effective Majorana mass, |M_{ee}|, and the branching ratios of the decays H^{\pm\pm}\to l^\pm {l'}^\pm, l,{l'}= e,μ, of the doubly charged Higgs boson H^{\pm\pm} is analysed within the Higgs Triplet Model of neutrino mass generation. We work in the version of the model with explicit breaking of the total lepton charge conservation, in which H^{\pm\pm}\to l^\pm {l'}^\pm, l,{l'} = e,μ,τ, are the dominant decay modes of H^{\pm\pm}. It is assumed also that H^{\pm\pm} are relatively light so that they can be produced at LHC and the branching ratios of interest measured. Taking into account the current and prospective uncertainties in the values of the neutrino mixing parameters most relevant for the problem studied - the atmospheric neutrino mixing angle θ_{23} and the CHOOZ angle θ_{13}, and allowing the lightest neutrino mass and the CP violating Dirac and Majorana phases to vary in the intervals [0, 0.3 eV] and [0, 2π], respectively, we derive the regions of values of BR(H^{\pm\pm}\to e^\pm e^\pm) and BR(H^{\pm\pm}\to e^\pm μ^\pm) for which |M_{ee}|\geq 0.05 eV, or |M_{ee}| < 0.05 eV. This is done for neutrino mass spectrum with normal ordering, inverted ordering and in the case when the type of the spectrum is not known, and i) without using the possible additional data on BR(H^{\pm\pm}\to μ^\pm μ^\pm), ii) using prospective data on BR(H^{\pm\pm}\to μ^\pm μ^\pm). In the latter case results for several values of BR(H^{\pm\pm}\to μ^\pmμ^\pm) are presented.

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CP Violation and Lightest Neutrino Mass Effects in Thermal Leptogenesis

Effects of the lightest neutrino mass in "flavoured" leptogenesis when the CP-violation necessary for the generation of the baryon asymmetry of the Universe is due exclusively to the Dirac and/or Majorana phases in the neutrino mixing matrix $U$ are discussed. The type I see-saw scenario with three heavy right-handed Majorana neutrinos having hierarchical spectrum is considered. The "orthogonal" parametrisation of the matrix of neutrino Yukawa couplings, which involves a complex orthogonal matrix $R$, is employed. Results for light neutrino mass spectrum with normal and inverted ordering (hierarchy) are reviewed.

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Effects of Lightest Neutrino Mass in Leptogenesis

The effects of the lightest neutrino mass in ``flavoured'' leptogenesis are investigated in the case when the CP-violation necessary for the generation of the baryon asymmetry of the Universe is due exclusively to the Dirac and/or Majorana phases in the neutrino mixing matrix U. The type I see-saw scenario with three heavy right-handed Majorana neutrinos having hierarchical spectrum is considered. The ``orthogonal'' parametrisation of the matrix of neutrino Yukawa couplings, which involves a complex orthogonal matrix R, is employed. Results for light neutrino mass spectrum with normal and inverted ordering (hierarchy) are obtained. It is shown, in particular, that if the matrix R is real and CP-conserving and the lightest neutrino mass m_3 in the case of inverted hierarchical spectrum lies the interval 5 \times 10^{-4} eV < m_3 < 7 \times 10^{-3} eV, the predicted baryon asymmetry can be larger by a factor of \sim 100 than the asymmetry corresponding to negligible m_3 \cong 0. As consequence, we can have successful thermal leptogenesis for 5 \times 10^{-6} eV < m_3 < 5 \times 10^{-2} eV even if R is real and the only source of CP-violation in leptogenesis is the Majorana and/or Dirac phase(s) in U.

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Flavour physics of leptons and dipole moments

This chapter of the report of the ``Flavour in the era of the LHC'' Workshop discusses the theoretical, phenomenological and experimental issues related to flavour phenomena in the charged lepton sector and in flavour-conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavour structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the Standard Model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

hep-ph

The See-Saw Mechanism, Neutrino Yukawa Couplings, LFV Decays l_i to l_j + gamma and Leptogenesis

The LFV charged lepton decays mu to e + gamma, tau to e + gamma and tau to mu + gamma and thermal leptogenesis are analysed in the MSSM with see-saw mechanism of neutrino mass generation and soft SUSY breaking with universal boundary conditions. The case of hierarchical heavy Majorana neutrino mass spectrum, M_1 << M_2 << M_3, is investigated. Leptogenesis requires M_1 > 10^9 GeV. Considering the natural range of values of the heaviest right-handed Majorana neutrino mass, M_3 > 5*10^{13} GeV, and assuming that the soft SUSY breaking universal gaugino and/or scalar masses have values in the range of few 100 GeV, we derive the combined constraints, which the existing stringent upper limit on the mu to e + gamma decay rate and the requirement of successful thermal leptogenesis impose on the neutrino Yukawa couplings, heavy Majorana neutrino masses and SUSY parameters. Results for the three possible types of light neutrino mass spectrum -- normal and inverted hierarchical and quasi-degenerate -- are obtained.

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Majorana CP-Violating Phases, RG Running of Neutrino Mixing Parameters and Charged Lepton Flavour Violating Decays

We consider the MSSM with see-saw mechanism of neutrino mass generation and soft SUSY breaking with flavour-universal boundary conditions at the GUT scale, in which the lepton flavour violating (LFV) decays μ\to e + γ, τ\to μ+ γ, etc.,are predicted with rates that can be within the reach of present and planned experiments. These predictions depend critically on the matrix of neutrino Yukawa couplings \bf{Y_ν} which can be expressed in terms of the light and heavy right-handed (RH) neutrino masses, neutrino mixing matrix U_{PMNS}, and an orthogonal matrix \bf{R}. We investigate the effects of Majorana CP-violation phases in U_{PMNS}, and of the RG running of light neutrino masses and mixing angles from M_Z to the RH Majorana neutrino mass scale M_R, on the predictions for the rates of LFV decays μ\to e + γ, τ\to μ+ γand τ\to e + γ. Results for neutrino mass spectrum with normal hierarchy, values of the lightest ν-mass in the range 0 \leq m_1 \leq 0.30 eV, and quasi-degenerate heavy RH Majorana neutrinos in the cases of \bf{R} = \bf{1} and complex matrix \bf{R} are presented. We find that the effects of the Majorana CP-violation phases and of the RG evolution of neutrino mixing parameters can change by few orders of magnitude the predicted rates of the LFV decays μ\to e + γand τ\to e + γ. The impact of these effects on the τ\to μ+ γdecay rate is typically smaller and only possible for m_1 > 0.10 eV. If the RG running effects are negligible, in a large region of soft SUSY breaking parameter space the ratio of the branching ratios of the μ\to e + γand τ\to e + γ(τ\to μ+ γ) decays is entirely determined in the case of \bf{R} \cong \bf{1} by the values of the neutrino mixing parameters at M_Z.

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Masses and Mixing of Quarks and Leptons in Product-Group Unification

We discuss a supersymmetric unified model based on a product gauge group SU(5)\times SU(5)\times SU(5), where the gauge symmetry breaking is achieved without the adjoint or higher-dimensional Higgs field, and the doublet-triplet splitting in the Higgs masses is realized by the use of the discrete symmetry. In this article we present an explicit model for realistic fermion masses with the discrete symmetries Z_7\times Z_2. It is shown that all the observed masses and mixing angles for quarks and leptons, including neutrinos, are well described by the breaking of the symmetries imposed in the model. Especially, the maximal and large mixing angles in the atmospheric and solar neutrino oscillations are obtained as the most preferred values, and the typical value of the neutrino mixing element U_{e3} is 0.1-0.3. We also point out the non-trivial relations among the μ-parameter for the Higgs mass, the charged fermion hierarchies, and the neutrino masses. These relations suggest that the scale of μis of order of the weak scale.

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Green-Schwarz Anomaly Cancellation, World Sheet Instantons and Wormholes

We consider the breaking of the global conservation of gauge field charges which are commonly thought to survive the spontaneous breakdown of gauge symmetry brought about by Kalb-Ramond fields. Depending on the dilaton field and also the size of the compactifying space, the global charge breaking may take place due to world sheet instantons. In going to 3+1 dimensions one could have a serious problem in order to produce the hierarchies between the quark and the charged lepton masses using the mass protecting charges with the Green-Schwartz anomaly cancellation. Various unnatural features of this type of models are discussed.

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Charged Lepton Flavor Violating Decays: Leading Logarithmic Approximation versus Full RG Results

In the context of the minimal supersymmetric extension of the Standard Model with the right-handed Majorana neutrinos, we study lepton flavor violating processes including full renormalization group running effects. We systematically compare our results with the commonly used leading logarithmic approximation, resorting to a ``best fit'' approach to fix all the high energy Yukawa matrices. We find significant deviations in large regions of the SUSY parameter space, which we outline in detail. We also give, within this setting, some results on the cosmo-phenomenologically preferred stau coannihilation region. Finally, we propose a parametrization, in terms of the SUSY input parameters, of the common SUSY mass appearing in the leading log and mass insertion approximation formula for the charged lepton flavor violating decay rates, which fits our full renormalization group results with high precision.

hep-ph

Family Replicated Gauge Group Models

Family Replicated Gauge Group models of the type SU(n)^N\times SU(m)^N, (SMG)^3 and (SMG\times U(1)_{B-L})^3 are reviewed, where SMG=SU(3)_{c}\times SU(2)_{L}\times U(1)_{Y} is the gauge symmetry group of the Standard Model, $B$ is the baryon and $L$ is the lepton numbers, respectively. It was shown that Family Replicated Gauge Group model of the latter type fits the Standard Model fermion masses and mixing angles and describes all neutrino experiment data order magnitudewise using only 5 free parameters -- five vacuum expectation values of the Higgs fields which break the Family Replicated Gauge Group symmetry to the Standard Model. The possibility of [SU(5)]^3 or [SO(10)]^3 unification at the GUT-scale \sim 10^{18} GeV also is briefly considered.

hep-ph

Proceedings to the workshops 'What comes beyond the Standard model', 2000, 2001, 2002, Volume 2: Proceedings (Part II)

Contents (Part 2): 8.Renormalization of Coupling Constants in the Minimal SUSY Models (R. B. Nevzorov, K. A. Ter-Martirosyan and M. A. Trusov) 9.Multiple Point Model and Phase Transition Couplings ...(L.V. Laperashvili, D.A. Ryzhikh and H.B. Nielsen) 10.Family Replicated Fit of All Quark and Lepton Masses and Mixings (H. B. Nielsen and Y. Takanishi) 11.Family Replicated Calculation of Baryogenesis (H. B. Nielsen and Y. Takanishi) 12. Neutrino Oscillations in Vacuum on the Large Distance (D.A. Ryzhikh and K.A. Ter-Martirosyan) 13. Possibility of an Additional Source of Time Reversal Violation for Neutrinos (R. Erdem) 14.Quark-Lepton Masses and the Neutrino Puzzle in the AGUT Model (C.D. Froggatt) 15.Neutrinos in the Family Replicated Gauge Group Model (C.D. Froggatt) (Contents of Part 1 [hep-ph/0301029]: 1.Derivation of Lorentz Invariance and Three Space Dimensions in Generic Field Theory (C D. Froggatt and H. B. Nielsen) 2.Unitary Representations, Noncompact Groups SO(q; d - q)...(N. Mankoc Borstnik, H. B. Nielsen and D. Lukman) 3.Weyl Spinor of SO(1; 13), Families of Spinors ...(A. Borstnik Bracic and N. Mankoc Borstnik) 4.A Tight Packing Problem (A. Kleppe) 5.Why so Few Particle Species? ... (D.L. Bennett and A. Kleppe) 6.About Number of Families (D. Lukman, A. Kleppe and N.S. Mankoc Borstnik) 7.Coupling Constant Unification in Spin-Charge Unifying Model ....(N. Mankoc Borstnik and H. B. Nielsen))

hep-ph

Non-thermal Leptogenesis from the Heavier Majorana Neutrinos

We investigate a scheme for making leptogenesis by means of the CP violating decays of the seesaw Majorana neutrinos proposed by Fukugita and Yanagida. However, in order to avoid the wash-out of the produced lepton number we propose the production of the Majorana neutrinos to occur non-thermally and sufficiently late. After this time, in consequence, the B-L (baryon minus lepton) quantum number becomes a good ``accidental symmetry'' protecting the asymmetry produced. This non-thermal leptogenesis at late time is realized by a boson decaying into the Majorana neutrinos with a long lifetime. Suggestively this boson could correspond to a scalar field which causes the cosmic inflation, the inflaton, and thus its decay means really the reheating of the Universe. We find that this mechanism works well even if the lightest Majorana neutrinos are not produced sufficiently or not present, and the decays of the heavier seesaw Majorana neutrinos can be responsible to the baryon asymmetry in the present Universe, as we illustrate by the example of the family replicated gauge group model.

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Five Adjustable Parameter Fit of Quark and Lepton Masses and Mixings

We develop a model of ours fitting the quark and lepton masses and mixing angles by removing from the model a Higgs field previously introduced to organise a large atmospheric mixing angle for neutrino oscillations. Due to the off-diagonal elements dominating in the see-saw neutrino mass matrix the large atmospheric mixing angle comes essentially by itself. It turns out that we have now only five adjustable Higgs field vacuum expectation values needed to fit all the masses and mixings order of magnitudewise taking into account the renormalisation group runnings in all sectors. The CHOOZ angle comes out close to the experimental bound.

hep-ph

Baryogenesis via Lepton Number Violation and Family Replicated Gauge Group

We developed a previous model fitting all quark and lepton -- including neutrino quantities in the region of the Large Mixing Angle-MSW solar solution -- order of magnitudewise by only six adjustable parameters (Higgs vacuum expectation values) to also give an agreeing prediction for the amount of baryogenesis produced in the early time of cosmology. We use Fukugita-Yanagida scheme and take into account now also the effect of the remormalisation equation for the Dirac neutrino sector from Planck scale to the see-saw scale. The present version of our model with many approximately conserved (gauge) charges distinguishing various left- and right-Weyl particles has the largest matrix element of the mass matrix for the three flavour see-saw neutrinos being the off-diagonal elements associated with the second- and third-proto-flavour and gives the ratio of baryon number density to the entropy density to 2.59{+17.0\atop-2.25}\times 10^{-11} which agrees perfectly well as do also all the fermion masses and their mixing angles order of magnitudewise.

hep-ph

Family replicated calculation of baryogenesis

In our model with a Standard Model gauge group extended with a baryon number minus lepton number charge for each family of quarks and leptons, we calculate the baryon number relative to entropy produced in early Big Bang by the Fukugita-Yanagida mechanism. With the parameters, i.e., the Higgs VEVs already fitted in a very successful way to quark and lepton masses and mixing angles we obtain the order of magnitude pure prediction Y_B=2.59{+17.0\atop-2.25}\times 10^{-11} which according to a theoretical estimate should mean in this case an uncertainty of the order of a factor 7 up or down (to be compared to Y_B=(1.7-8.1)\times 10^{-11}) using a relatively crude approximation for the dilution factor, while using another estimate based on Buchmüller and Plümacher a factor 500 less, but this should rather be considered a lower limit. With a realistic uncertainty due to wash-out of a factor 100 up or down we even with the low estimate only deviate by 1.5σ.

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Family replicated fit of all quark and lepton masses and mixings

We review our recent development of family replicated gauge group model, which generates the Large Mixing Angle MSW solution. The model is based on each family of quarks and leptons having its own set of gauge fields, each containing a replica of the Standard Model gauge fields plus a (B-L)-coupled gauge field. A fit of all the seventeen quark-lepton mass and mixing angle observables, using just six new Higgs field vacuum expectation values, agrees with the experimental data order of magnitudewise. However, this model can not predict the baryogenesis in right order, therefore, we discuss further modification of our model and present a preliminary result of baryon number to entropy ratio.

hep-ph

Family replicated gauge groups and large mixing angle solar neutrino solution

We present a modification of our previous family replicated gauge group model, which now generates the Large Mixing Angle MSW solution rather than the experimentally disfavoured Small Mixing Angle MSW solution to the solar neutrino oscillation problem. The model is based on each family of quarks and leptons having its own set of gauge fields, each containing a replica of the Standard Model gauge fields plus a (B-L)-coupled gauge field. By a careful choice of the Higgs field gauge quantum numbers, we avoid our previous prediction that the solar neutrino mixing angle is equal order of magnitudewise to the Cabibbo angle, replacing it and the well-known Fritzsch relation with the relation θ_{c}\sim (θ_{\odot})^{-1/3} (m_d/m_s)^{2/3}. At the same time we retain a phenomenologically successful structure for the charged quark and lepton mass matrices. A fit of all the seventeen quark-lepton mass and mixing angle observables, using just six new Higgs field vacuum expectation values, agrees with the experimental data within the theoretically expected uncertainty of about 64%, i.e. it fits perfectly order of magnitudewise.

hep-ph

Standard Model Higgs Boson Mass from Borderline Metastability of the Vacuum

We have studied imposing the condition that the Standard Model effective Higgs potential should have two approximately degenerate vacua, such that the vacuum we live in is just barely metastable: the one in which we live has a vacuum expectation value of 246 GeV and the other one should have a vacuum expectation value of order the Planck scale. Alone borderline metastability gives, using the experimental top quark mass 173.1 \pm 4.6 GeV, the Higgs mass prediction 121.8 \pm 11 GeV. The requirement that the second minimum be at the Planck scale already gave the prediction 173\pm 4 GeV for the top quark mass according to our 1995 paper.

hep-ph