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Jisuke Kubo

Publications and source records attributed to Jisuke Kubo.

At least 73 records · Page 4Linked to original sources
arXiv2004

Higgs Potential in Minimal S_3 Invariant Extension of the Standard Model

Minimal $S_{3}$ invariant Higgs potential with real soft $S_{3}$ breaking masses is investigated. It is required that without having a problem with triviality, all physical Higgs bosons, except one neutral one, become heavy ~O(10) TeV in order to sufficiently suppress flavor changing neutral currents. There exist three nonequivalent soft mass terms that can be characterized according to their discrete symmetries, and the one which breaks $S_{3}$ completely. The $S_{2}'$ invariant vacuum expectation values (VEVs) of the Higgs fields are the most economic VEVs in the sense that the freedom of VEVs can be completely absorbed into the Yukawa couplings so that it is possible to derive, without referring to the details of the VEVs, the most general form for the fermion mass matrices in minimal $S_{3}$ extension of the standard model. We find that except for the completely broken case of the soft terms, the $S_{2}'$ invariant VEVs are unique VEVs that satisfy the requirement of heavy Higgs bosons. It is found that they also correspond to a local minimum in the completely broken case.

hep-ph↗
arXiv2004

Double Suppression of FCNCs in Supersymmetric Models

A mechanism for double suppression of flavor-changing neutral currents (FCNCs) and CP violating phases in supersymmetric models is suggested. At M_{SUSY} they are suppressed due to a nonabelian discrete flavor symmetry, and the infrared attractive force of gauge interactions in extra dimensions are used to suppress them at the compactification scale. We present a concrete model, which is a simple extension of S_{3} invariant minimal supersymmetric standard model, where only SU(2)_{L} and SU(3)_{C} gauge multiplets are assumed to propagate in the bulk. We find that a disorder of two orders of magnitude in soft supersymmetry breaking parameters above the compactification scale may be allowed to satisfy experimental constraints on FCNC processes and CP violating phenomena.

hep-ph↗
arXiv2003

Softening the Supersymmetric Flavor Problem in Orbifold GUTs

The infra-red attractive force of the bulk gauge interactions is applied to soften the supersymmetric flavor problem in the orbifold SU(5) GUT of Kawamura. Then this force aligns in the infra-red regime the soft supersymmetry breaking terms out of their anarchical disorder at a fundamental scale, in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are suppressed at low energies. It is found that this dynamical alignment is sufficiently good compared with the current experimental bounds, as long as the diagonalization matrices of the Yukawa couplings are CKM-like.

hep-ph↗
arXiv2003

Maximal Locality and Predictive Power in Higher-Dimensional, Compactified Field Theories

To achieve a maximal locality in a trivial field theory, we maximize the ultraviolet cutoff of the theory by fine tuning the infrared values of the parameters. This optimization procedure is applied to the scalar theory in $D+1$ dimensions ($D \geq 4$) with one extra dimension compactified on a circle with radius $R$. The optimized, infrared values of the parameters are then compared with the corresponding ones of the uncompactified theory in $D$ dimensions, which is assumed to be the low-energy effective theory. We find that these values approximately agree with each other, as long as $R^{-1} \gsim s M$ is satisfied, where $s\simeq 10,50,50, 100$ for $D=4,5,6,7$, and $M$ is a typical scale of the $D$-dimensional theory. This result supports the previously made claim that the maximization of the ultraviolet cutoff in an nonrenormalizable field theory can give the theory more predictive power.

hep-th↗
arXiv2003

Exact $S_3$ symmetry solving the supersymmetric flavor problem

The exact discrete flavor symmetry, $S_3$ in the hadronic sector and $S_3 \times Z_2$ in the leptonic sector, which has been recently found, is introduced in a supersymmetric extension of the standard model. We investigate the supersymmetric flavor problem, and explicitly find that thanks to the flavor symmetry the dangerous FCNC processes and CP-violating phases are sufficiently suppressed.

hep-ph↗
arXiv2002

Finite Theories and the SUSY Flavor Problem

We study a finite SU(5) grand unified model based on the non-Abelian discrete symmetry A_4. This model leads to the democratic structure of the mass matrices for the quarks and leptons. In the soft supersymmetry breaking sector, the scalar trilinear couplings are aligned and the soft scalar masses are degenerate, thus solving the SUSY flavor problem.

hep-ph↗
arXiv2002

Suppressing FCNC and CP-Violating Phases with Extra Dimensions

The infrared attractiveness of soft-supersymmetry breaking (SSB) parameters is investigated in extra dimensions. The SSB parameters are assumed to run from the Planck scale M_{PL} down to the GUT scale M_{GUT}. We find that, even for M_{PL}/M_{GUT}=100, the SSB parameters in six dimensions can align out of their anarchical disorder at M_{PL} in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are sufficiently suppressed at M_{GUT}. A concrete, realistic example based on SU(5) in six dimensions is presented.

hep-ph↗
arXiv2002

Unrenormalizable Theories Can Be Predictive

Unrenormalizable theories contain infinitely many free parameters. Considering these theories in terms of the Wilsonian renormalization group (RG), we suggest a method for removing this large ambiguity. Our basic assumption is the existence of the maximal ultraviolet cutoff in a cutoff theory, and we require that the theory be so fine-tuned as to reach the maximal cutoff. The theory so obtained behaves as a local continuum theory to the shortest distance. In concrete examples of the scalar theory we find that at least in a certain approximation to the Wilsonian RG, this requirement enable us to make unique predictions in the infrared regime in terms of a finite number of independent parameters. Therefore, the method might provide a way for calculating quantum corrections in a low-energy effective theory of quantum gravity.

hep-th↗
arXiv2002

Suppressing FCNC and CP-Violating Phases by Extra Dimensions

In extra dimensions the infrared attractive force of gauge interactions is amplified. We find that this force can align in the infrared limit the soft-supersymmetry breaking terms out of their anarchical disorder at a fundamental scale, in such a way that flavor-changing neutral currents as well as dangerous CP-violating phases are sufficiently suppressed at the unification scale. The main assumption is that the matter and Higgs supermultiplets and the flavor-dependent interactions such as Yukawa interactions are stuck at the four-dimensional boundary. As a concrete example we consider the minimal model based on SU(5) in six dimensions.

hep-ph↗
arXiv2002

Scaling Laws and Effective Dimension in Lattice SU(2) Yang-Mills Theory with a Compactified Extra Dimension

Monte Carlo simulations are performed in a five-dimensional lattice SU(2) Yang-Mills theory with a compactified extra dimension, and scaling laws are studied. Our simulations indicate that as the compactification radius $R$ decreases, the confining phase spreads more and more to the weak coupling regime, and the effective dimension of the theory changes gradually from five to four. Our simulations also indicate that the limit $a_4 to 0$ with $R/a_4$ kept fixed exists both in the confining and deconfining phases if $R/a_4$ is small enough, where $a_4$ is the lattice spacing in the four-dimensional direction. We argue that the color degrees of freedom in QCD are confined only for $R < R_{\rm max}$, where a rough estimate shows that $1/R_{\rm max}$ lies in the TeV range. Comments on deconstructing extra dimensions are given.

hep-lat↗
arXiv2001

Suppressing the $μ$ and neutrino masses by a superconformal force

The idea of Nelson and Strassler to obtain a power law suppression of parameters by a superconformal force is applied to understand the smallness of the $μ$ parameter and neutrino masses in R-parity violating supersymmetric standard models. We find that the low-energy sector should contain at least another pair of Higgs doublets, and that a suppression of $\lsim O(10^{-13})$ for the $μ$ parameter and neutrino masses can be achieved generically. The superpotential of the low-energy sector happens to possess an anomaly-free discrete R-symmetry, either $R_3$ or $R_6$, which naturally suppresses certain lepton-flavor violating processes, the neutrinoless double beta decays and also the electron electric dipole moment. We expect that the escape energy of the superconformal sector is $\lsim$ O(10) TeV so that this sector will be observable at LHC. Our models can accommodate to a large mixing among neutrinos and give the same upper bound of the lightest Higgs mass as the minimal supersymmetric standard model.

hep-ph↗
arXiv2000

Extra dimensions prefer large $\tanβ$

Assuming that the recent result obtained from the Monte Carlo simulations on the nonperturbative existence of the pure SU(2) Yang-Mills theory in five dimensions can be applied to a more general class of higher-dimensional gauge theories, we derive the conditions imposed by the nontriviality requirement on the theories. We find that the supersymmetric grand unified theories with extra dimensions prefer a large value ($\gsim 2$) of $\tanβ$ of the minimal supersymmetric standard model, in accord with today's possible observation of the Higgs particle at LEP2.

hep-ph↗
arXiv2000

Running couplings in extra dimensions

The regularization scheme dependence of running couplings in extra compactified dimensions is discussed. We examine several regularization schemes explicitly in order to analyze the scheme dependence of the Kaluza-Klein threshold effects, which cause the power law running, in the case of the scalar theory in five dimensions with one dimension compactified. It is found that in 1-loop order, the net difference in the running of the coupling among the different schemes is reduced to be rather small after finite renormalization. An additional comment concerns the running couplings in the warped extra dimensions which are found to be regularization dependent above TeV scale.

hep-ph↗
arXiv2000

A Study on the Non-perturbative Existence of Yang-Mills Theories with Large Extra Dimensions

Pure lattice SU(2) Yang-Mills theory in five dimensions is considered, where an extra dimension is compactified on a circle. Monte-Carlo simulations indicate that the theory possesses a continuum limit with a non-vanishing string tension if the compactification radius is smaller than a certain value $R_M$ which is $O(1/10)$ of the inverse of the square root of the string tension. We verify non-perturbatively the power-law running of gauge coupling constant. Our method can be applied to the investigation of continuum limits in other higher-dimensional gauge theories.

hep-ph↗
arXiv1999

Kaluza-Klein Thresholds and Regularization (In)dependence

We present a method to control the regularization scheme dependence in the running of couplings in Kaluza-Klein theories. Specifically we consider the scalar theory in five dimensions, assuming that one dimension is compactified and we study various regularization schemes in order to analyze concretely the regularization scheme dependence of the Kaluza-Klein threshold effects. We find that in one-loop order, although the $β$-functions are different for the different schemes, the net difference in the running of the coupling among the different schemes is very small for the entire range of energies. Our results have been extended to include more than one radii, and the gauge coupling unification is re-examined. Strings are also used as a regulator. We obtain a particular regularization of effective field theory which can accurately describe the string Kaluza-Klein threshold effects.

hep-ph↗
arXiv1999

Electroweak symmetry breaking and s-spectrum in M-theory

We study soft SUSY breaking parameters in M-theory with and without 5-brane moduli fields. We investigate successful electroweak symmetry breaking and the positivity of stau mass squared. We study mass spectra in allowed regions.

hep-ph↗
arXiv1999

Applications of the Reduction of Couplings

Applications of the principle of reduction of couplings to the standard model and supersymmetric grand unified theories are reviewed. Phenomenological applications of renormalization group invariant sum rules for soft supersymmetry-breaking parameters are also reviewed.

hep-ph↗