arXiv subjects

Koichi Yoshioka

Publications and source records attributed to Koichi Yoshioka.

At least 55 records · Page 3Linked to original sources

arXiv2004

Radiative stabilization of warped space

Higher-dimensional field theory has been applied to explore various issues in recent particle physics such as the gauge hierarchy problem. In order for such approaches to be viable, a crucial ingredient is to fix the sizes of extra dimensions at some finite values, which sizes are generically free parameters in the theory. In this paper, we present several schemes to determine the radius of extra dimension in warped five-dimensional theory. In every case, a non-vanishing Fayet-Iliopoulos term for abelian gauge factor plays a crucial role for the radius stabilization. It is radiatively generated in the presence of charged matter fields and the compactification is therefore spontaneous, not forced by selected operators. The low-energy supersymmetry is broken or unbroken, and the radius can be fixed to give a small or large scale hierarchy without any fine tuning of parameters. We also discuss a model of the radius stabilization correlated with Yukawa hierarchy and supersymmetry breaking.

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arXiv2004

Anomalies and Fayet-Iliopoulos terms on warped orbifolds and large hierarchies

The anomalies in five-dimensional orbifold theories are examined in a generic type of non-factorizable geometries. In spite of complicated fermion wavefunctions, the shape of anomaly is found to be identical to that of flat theories. In particular it is split evenly on the orbifold fixed points. This result also follows from the arguments on the AdS/CFT correspondence and an anomaly cancellation mechanism. The cancellation with Chern-Simons term works if the four-dimensional effective theory is free from chiral anomalies. We also discuss the Fayet-Iliopoulos (FI) term in warped supersymmetric theories. Unlike the gauge anomaly, FI divergences reside not only on the orbifold fixed points but also in the whole five-dimensional bulk. The effect of the FI term is to generate supersymmetric masses for charged hypermultiplets, which are no longer constant but have metric factor dependence. We calculate the spectrum and wavefunctions of Kaluza-Klein modes in the presence of the FI term and discuss phenomenological implications to quark-lepton masses and large scale hierarchies.

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arXiv2004

Radiative CP Phases in Supergravity Theories

In this letter, we point out that possible sources of CP violation originate from radiative corrections to soft terms which are ubiquitous in supergravity theories and also in other high-energy frameworks of supersymmetry breaking. With these radiative phases of gaugino masses and scalar couplings, a complex phase of Higgs holomorphic mass parameter is generated via renormalization-group running down to low energy. It is found that its phase value is mainly controlled by wino as well as gluino, which generally receive different radiative corrections to their complex phases, even if the leading part of mass parameters follow from the universality hypothesis. The radiatively generated phases are constrained by the existing experimental bounds on electric dipole moments, and may be detectable in future measurements. They are also found to be available for the cancellation mechanism to be worked.

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arXiv2003

Sparticle Masses in Product-Group Gauge Theories

In this paper, we investigate a possibility to cause supersymmetry breaking with background modulus fields in product-group gauge theories. The vacuum expectation values of these moduli are found to satisfy several relations and the moduli dependences of the action are fixed by consistency of the model. With this action, we calculate the mass spectrum of vector and matter multiplets up to one-loop order of perturbation theory. As an application of the result, it is found that various properties of higher-dimensional supersymmetry breaking are well captured in corresponding limits in the moduli space. In particular, we have finite radiative corrections to Higgs masses in the case that is closely related to the boundary condition breaking of supersymmetry.

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arXiv2003

Field localization in warped gauge theories

We present four-dimensional gauge theories that describe physics on five-dimensional curved (warped) backgrounds, which includes bulk fields with various spins (vectors, spinors, and scalars). Field theory on the AdS$_5$ geometry is examined as a simple example of our formulation. Various properties of bulk fields on this background, e.g., the mass spectrum and field localization behavior, can be achieved within a fully four-dimensional framework. Moreover, that gives a localization mechanism for massless vector fields. We also consider supersymmetric cases, and show in particular that the conditions on bulk masses imposed by supersymmetry on warped backgrounds are derived from a four-dimensional supersymmetric theory on the flat background. As a phenomenological application, models are shown to generate hierarchical Yukawa couplings. Finally, we discuss possible underlying mechanisms which dynamically realize the required couplings to generate curved geometries.

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arXiv2003

4D construction of bulk supersymmetry breaking

In this letter, we discuss a four-dimensional model with modulus fields which are responsible for supersymmetry breaking. Given non-trivial moduli dependence of the action, the model is found to give a proper description of higher-dimensional supersymmetry breaking. We explicitly calculate gaugino and scalar mass spectrum and show that several classes of scenarios proposed in the literature are described in certain regions of the parameter space of the moduli vacuum expectation values. The model in other generic regions of the moduli space gives unexplored scenarios (mass spectra) of supersymmetry breaking in four dimensions.

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arXiv2002

Flavor violation in supersymmetric theories with gauged flavor symmetries

In this paper we study flavor violation in supersymmetric models with gauged flavor symmetries. There are several sources of flavor violation in these theories. The dominant flavor violation is the tree-level $D$-term contribution to scalar masses generated by flavor symmetry breaking. We present a new approach for suppressing this phenomenologically dangerous effects by separating the flavor-breaking sector from supersymmetry-breaking one. The separation can be achieved in geometrical setups or in a dynamical way. We also point out that radiative corrections from the gauginos of gauged flavor symmetries give sizable generation-dependent masses of scalars. The gaugino mass effects are generic and not suppressed even if the dominant $D$-term contribution is suppressed. We also analyze the constraints on the flavor symmetry sector from these flavor-violating corrections.

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arXiv2002

Dynamical Solution to Supersymmetric CP Problem with Vanishing B Parameter

The CP violation gives rise to severe restriction of soft breaking terms in supersymmetric standard models. Among them, constraints on the holomorphic soft mass of Higgs doublets (the B parameter) are difficult to satisfy due to the other inherent problem in the Higgs potential; the mu problem. In this letter, it is argued that these CP and mu problems can be rather relaxed provided that B is vanishing at high-energy scale. A generic mechanism and some examples of model are presented to dynamically realize this condition by introducing gauge singlet fields.

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arXiv2001

Fermion Mass Hierarchies and Small Mixing Angles from Extra Dimensions

In this paper we study renormalization-group evolutions of Yukawa matrices enhanced by Kaluza-Klein excited modes and analyze their infrared fixed-point structure. We derive necessary conditions to obtain hierarchies between generations on the fixed point. These conditions restrict how the fields in the models can extend to higher dimension. Several specific mechanisms to realize the conditions are presented. We also take account of generation mixing effects and find a scenario where the mixing angles become small at low energy even with large initial values at high-energy scale. A toy model is shown to lead realistic quark mass matrices.

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arXiv2000

Kaluza-Klein Mediated Supersymmetry Breaking

We discuss a framework for communicating supersymmetry breaking to the visible sector where the radius modulus, which determines the size of extra dimensions, has an auxiliary vacuum expectation value. The modulus couplings generate mass splitting in Kaluza-Klein supermultiplets and they act as messengers of supersymmetry breaking. The soft masses are expressed in terms of renormalization-group functions and the sparticle spectrum is determined by what kind of field propagates in the bulk. This framework also provides new possibilities for solving the supersymmetric flavor problem.

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arXiv2000

Infrared alignment of SUSY flavor structures

The various experimental bounds on flavor-changing interactions severely restrict the low-energy flavor structures of soft supersymmetry breaking parameters. In this work, we show that with a particular assumption of Yukawa couplings, the fermion mass and sfermion soft mass matrices are simultaneously diagonalized by common mixing matrices and we then obtain an alignment solution for the flavor problems. The required condition is generated by renormalization group evolutions and achieved at low-energy scale independently of high-energy structures of couplings. In this case, the diagonal entries of the soft scalar mass matrices are determined by gaugino and Higgs soft masses. We also discuss possible realizations of this scenario and the characteristic sparticle spectrum in the models.

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arXiv2000

New RG-invariants of Soft Supersymmetry Breaking Parameters

We study new renormalization-group invariant quantities of soft supersymmetry breaking parameters other than the ratio of gaugino mass to gauge coupling squared by using the spurion method. The obtained invariants are useful to probe supersymmetry breaking and mu-term generation mechanisms at high-energy scale. We also discuss the convergence behavior of fixed points of supersymmetry breaking parameters.

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arXiv2000

Novel Relations between Lepton and Quark Mixings

A novel relation is found which gives the 2-3 lepton mixing angle in terms of quark masses and CKM mixing: \tanθ_{μτ}=(m_b/m_s)V_{cb}. This relation, which is remarkably in good agreement with the quark data and the large lepton mixing recently observed, is a kind of SO(10) GUT relation similar to the celebrated bottom-tau mass ratio in SU(5). The GUT models in which this relation hold should have a `twisted SO(10)' structure between the second and third generations, in order to really explain the large lepton mixing, or equivalently, the right-hand side of the relation.

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arXiv2000

Probing extra dimensions using Nambu-Goldstone bosons

We investigate a possibility that our four-dimensional world is a brane-like object embedded in a higher dimensional spacetime. In such a situation, the transverse coordinates of the brane become the Nambu-Goldstone bosons which appear as a result of spontaneous breaking of the translation symmetry. We determine the form of the effective action of the system, finding the explicit form of the vierbein induced on the brane in terms of the Nambu-Goldstone boson variables and the bulk vielbein. As was pointed out in the previous paper, the Kaluza-Klein mode couplings are suppressed by the effect of the brane fluctuation and the suppression is stronger if the brane tension is smaller. However, we here show that the brane tension cannot be arbitrarily small since the inverse of the brane tension gives the coupling constant of the Nambu-Goldstone bosons. A rather stringent bound is obtained for the brane tension and the fundamental (`string') scale from the consideration of the cooling process of the supernova.

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arXiv2000

Yukawa hierarchy from extra dimensions and infrared fixed points

We discuss the existence of hierarchy of Yukawa couplings in the models with extra spatial dimensions. The hierarchical structure is induced by the power behavior of the cutoff dependence of the evolution equations which yield large suppressions of couplings at the compactification scale. The values of coupling constants at this scale can be made stable almost independently of the initial input parameters by utilizing the infrared fixed point. We find that the Yukawa couplings converge to the fixed points very quickly because of the enhanced energy dependence of the suppression factor from extra dimensions as well as in the case of large gauge couplings at high-energy scale.

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arXiv2000

On fermion mass hierarchy with extra dimensions

Recently various phenomenological implications of the existence of extra space-time dimensions have been investigated. In this letter, we construct a model with realistic fermion mass hierarchy with (large) extra dimensions beyond the usual four dimensions. In this model, it is assumed that some matter fields live in the bulk and the others are confined on our four dimensional wall. It can naturally reproduce the quark and lepton mass hierarchy and mixing angles without any symmetry arguments. We also discuss some possibilities of obtaining suitable neutrino masses and mixings for the solar and atmospheric neutrino problems.

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arXiv1999

Duality between simple-group gauge theories and some applications

In this paper we investigate N=1 supersymmetric gauge theories with a product gauge group. By using smoothly confining dynamics, we can find new dualities which include higher-rank tensor fields, and in which the dual gauge group is simple, not a product. Some of them are dualities between chiral and non-chiral gauge theories. We also discuss some applications to dynamical supersymmetry breaking phenomena and new confining theories with a tree-level superpotential.

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arXiv1998

Right-handed neutrino mass and bottom-tau ratio in strong coupling unification

The recent results of neutrino experiments indicate the existence of the right-handed neutrinos with masses around intermediate scale, which affects the prediction of the bottom-tau mass ratio. In the minimal supersymmetric standard model, this effect largely depends on the right-handed neutrino mass scale and then may severely limit its lower bound. In this letter, we show that in the case of strong coupling unification the bottom-tau mass ratio is little affected by the presence of the right-handed neutrinos. This is because of the infrared fixed-point behavior of Yukawa couplings, which is a common feature of this kind of model.

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