arXiv subjects

Daijiro Suematsu

Publications and source records attributed to Daijiro Suematsu.

At least 55 records · Page 3Linked to original sources

arXiv2006

Neutrino masses and CDM in a non-supersymmetric model

We propose a model for neutrino mass generation based on both the tree-level seesaw mechanism with a single right-handed neutrino and one-loop radiative effects in a non-supersymmetric framework. The generated mass matrix is composed of two parts which have the same texture and produce neutrino mass eigenvalues and mixing suitable for the explanation of neutrino oscillations. The model has a good CDM candidate which contributes to the radiative neutrino mass generation. The stability of the CDM candidate is ensured by $Z_2$ which is the residual symmetry of a spontaneously broken U(1)$^\prime$. We discuss the values of $U_{e3}$ and also estimate the masses of the relevant fields to realize an appropriate abundance of the CDM.

hep-ph↗

arXiv2006

SUSY breaking based on Abelian gaugino kinetic term mixings

We present a SUSY breaking scenario based on Abelian gaugino kinetic term mixings between hidden and observable sectors. If an extra U(1) gaugino in the observable sector obtains a large mass through this mixing effect based on SUSY breaking in the hidden sector, soft SUSY breaking parameters in the MSSM may be affected by radiative effects due to this gaugino mass. New phenomenological aspects are discussed in such a SUSY breaking scenario.

hep-ph↗

arXiv2006

Cold Dark Matter, Radiative Neutrino Mass, mu to e gamma, and Neutrinoless Double Beta Decay

Two of the most important and pressing questions in cosmology and particle physics are: (1) What is the nature of cold dark matter? and (2) Will near-future experiments on neutrinoless double beta decay be able to ascertain that the neutrino is a Majorana particle, i.e. its own antiparticle? We show that these two seemingly unrelated issues are intimately connected if neutrinos acquire mass only because of their interactions with dark matter.

hep-ph↗

arXiv2006

Singlino dominated LSP as CDM candidate in supersymmetric models with an extra U(1)

We consider a singlino dominated neutralino in supersymmetric models with an extra U(1). In case both the $μ$ term and also the $Z^\prime$ mass are generated by the vacuum expectation value of the scalar component of the same singlet chiral superfield, generically the lightest neutralino is not expected to be dominated by the singlino. However, if the gaugino corresponding to the extra U(1) is sufficiently heavy, the lightest neutralino can be dominated by the singlino and still satisfy the constraints resulting from the $Z^\prime$ phenomenology. We assume a supersymmetry breaking scenario in which the extra U(1) gaugino can be much heavier than other gauginos. In that framework we show that the singlino dominated lightest neutralino may be a good candidate for dark matter in a parameter space where various phenomenological constraints are satisfied.

hep-ph↗

arXiv2005

Dark world and baryon asymmetry from a common source

We study generation of baryon number asymmetry and both abundance of dark matter and dark energy on the basis of global symmetry and its associating flat directions in a supersymmetric model. We assume the existence of a model independent axion which is generally expected in the effective theory of superstring. If we consider a combined field of the model independent axion and a pseudo Nambu-Goldstone boson coming from spontaneous breaking of the global symmetry, its potential can be sufficiently flat and then it may present a candidate of the dark energy as a quintessential axion. Both the baryon asymmetry and the dark matter are supposed to be produced nonthermally as the asymmetry of another global charge through the Affleck-Dine mechanism along the relevant flat direction. Its decay to the observable and hidden sectors explains the baryon number asymmetry and the dark matter abundance, respectively.

astro-ph↗

arXiv2005

Nonthermal production of baryon and dark matter

We study nonthermal production of baryon and dark matter. If we extend the MSSM by introducing some singlet chiral superfields so as to enlarge the conserved global symmetry, the abundance of the baryon and the dark matter in the universe may be explained as the charge asymmetry of that symmetry. In such a case, the baryon energy density and the dark matter energy density in the present universe can be correlated each other and take the similar order values naturally.

hep-ph↗

arXiv2005

$μ$-term as the origin of baryon and lepton number asymmetry

We study a possibility of combining an origin of the $μ$-term and the baryon and lepton number asymmetry. If we assume that the $μ$-term is generated through a flat direction of a singlet scalar field, the coherent oscillation of this condensate around its potential minimum can store the global U(1) charge asymmetry. The decay of this condensate can distribute this asymmetry into the lepton and baryon number asymmetry as far as its decay occurs at an appropriate temperature. We examine the compatibility between this scenario and the small neutrino mass generation based on both the ordinary seesaw mechanism and the bilinear R-parity violating terms.

hep-ph↗

arXiv2005

Neutrino texture saturating the CP asymmetry

We study a neutrino mass texture which can explain the neutrino oscillation data and also saturate the upper bound of the CP asymmetry $ε_1$ in the leptogenesis. We consider the thermal and non-thermal leptogenesis based on the right-handed neutrino decay in this model. A lower bound of the reheating temperature required for the explanation of the baryon number asymmetry is estimated as $O(10^8)$GeV for the thermal leptogenesis and $O(10^{6})$GeV for the non-thermal one.It can be lower than the upper bound of the reheating temperature imposed by the cosmological gravitino problem. An example of the construction of the discussed texture is also presented.

hep-ph↗

arXiv2003

mu problem in an extended gauge mediation supersymmetry breaking

We study the $μ$ problem and the radiative electroweak symmetry breaking in an extended gauge mediation supersymmetry breaking (GMSB) model, in which the messenger fields are assumed to couple to the different singlet fields due to the discrete symmetry. Since the spectrum of superpartners is modified, the constraint from the $μ$ problem can be relaxed in comparison with the ordinary GMSB at least from the viewpoint of radiative symmetry breaking. We study the consistency of the values of $μ$ and $B_μ$ with the radiative electroweak symmetry breaking and also the mass spectrum of superpartners. We present such a concrete example in a supersymmetric SU(5) unified model which is constructed from a direct product gauge structure by imposing the doublet-triplet splitting.

hep-ph↗

arXiv2003

Soft SUSY breaking masses in a unified model with doublet-triplet splitting

We study soft supersymmetry breaking parameters in a supersymmetric unified model which potentially solves the doublet-triplet splitting problem. In the model the doublet-triplet splitting is solved by the discrete symmetry which is allowed to be introduced due to the direct product structure of the gauge group. The messenger fields for the gauge mediated supersymmetry breaking are naturally embedded in the model. The discrete symmetry required by the doublet-triplet splitting makes the gaugino masses non-universal and also induces a different mass spectrum for the scalar masses from the ordinary minimal gauge mediation model. Independent physical CP phases can remain in the gaugino sector even after the R-transformation.

hep-ph↗

arXiv2002

D-term inflation and neutrino mass

We study a $D$-term inflation scenario in a model extended from the minimal supersymmetric standard model (MSSM) by two additional abelian factor groups focussing on its particle physics aspects. Condensates of the fields related to the inflation can naturally give a possible solution to both the $μ$-problem in the MSSM and the neutrino mass through their nonrenormalizable couplings to the MSSM fields. Mixings between neutrinos and neutralinos are also induced by some of these condensates. Small neutrino masses are generated by a weak scale seesaw mechanism as a result of these mixings. Moreover, the decay of the condensates may be able to cause the leptogenesis. Usually known discrepancy between both values of a Fayet-Iliopoulos $D$-term which are predicted by the COBE normalization and also by an anomalous U(1) in the weakly-coupled superstring might be reconciled.

hep-ph↗

arXiv2002

Neutrino mass due to the neutrino-gaugino mixing

We study a possibility to explain neutrino masses and mixings based on supersymmetry. If we introduce a flavor diagonal but generation dependent extra U(1) gauge interaction at a TeV region, we can obtain masses and mixings of neutrinos required for the explanation of both solar and atmospheric neutrinos. In this model, differently from the usual bilinear R-parity violating scenario, the neutrino mass degeneracy can be resolved at a tree level by the neutrino-gaugino mixing caused by an R-parity violation. The model is straightforwardly extended to include the quark sector by introducing an anomalous U(1) which can be used for the Froggatt-Nielsen mechanism.

hep-ph↗

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↗

arXiv2001

$μ$-term due to the non-universal supersymmetry breaking and the Higgs mass

We propose a solution to the $μ$-problem due to the non-universal soft supersymmetry breaking in a class of supersymmetric extensions of the SM with an extra U(1) and the NMSSM. Our scenario resembles an earlier one which has been proposed as a solution to the $μ$-problem in the framework of similar models but it has rather different features from that. Theoretically crucial points in the present scenario are the realization of the required non-universal soft supersymmetry breaking parameters and the concern to avoid the vacuum instability due to tadpoles. We discuss them in some detail. In particular, on the non-universal soft supersymmetry breaking we discuss the superstring and the field theory with reduction of couplings possibilities. We also study the weak scale radiative symmetry breaking in the considered models and estimate the upper mass bound of the lightest neutral Higgs scalar. The latter tends to be smaller in the present scenario as compared to the previous one.

hep-ph↗

arXiv2001

A light sterile neutrino based on the seesaw mechanism

We propose a simple model of the neutrino mass matrix which can explain the solar and atmospheric neutrino problems in a 3($ν_L + ν_R$) framework. Assuming that only two right-handed neutrinos are heavy and a Dirac mass matrix has a special texture, we construct a model with four light neutrinos. The favorable structure of flavor mixings and mass eigenvalues required by those neutrino deficits is realized as a result of the seesaw mechanism. Bi-maximal mixing structure might be obtainable in this scheme. Since it contains a light sterile neutrino, it has a chance to explain the LSND result successfully. We consider an embedding of this scenario for the neutrino mass matrix into the SU(5) grand unification scheme using the Froggatt-Nielsen mechanism based on $U(1)_{F_1} \times U(1)_{F_2}$. Both a small mixing angle MSW solution and a large mixing angle MSW solution are obtained for the solar neutrino problem depending on the charged lepton mass matrix.

hep-ph↗

arXiv2001

The origin of quark and lepton mixings

We propose a model for the mass matrices of quarks and leptons based on two Abelian flavor symmetries. One is assumed to be broken at a high energy region near the Planck scale. It is used for the Froggatt-Nielsen mechanism in both quark and charged lepton sectors. Another one remains unbroken to a multi-TeV region. The mixings among neutrinos and gauginos including the one of the new Abelian symmetry generate non-zero masses and mixings among neutrinos. A bi-maximal scheme for the neutrino oscillation can be realized together with suitable masses and CKM-mixings in the quark sector. FCNC constraints on this flavor dependent Abelian symmetry seems to be evaded.

hep-ph↗

arXiv2001

Neutrino mass due to the mixing among neutrinos and gauginos

We consider the explanation of both data of the atmospheric neutrino and the solar neutrino by the neutrino mass matrix derived from the mixing of neutrinos and gauginos in the extended MSSM with an extra U(1) gauge symmetry. This scenario directly relates the neutrino mass to supersymmetry. The structure of the mass hierarchy and the mixing is determined only by the extra U(1)-charge of neutrinos. Although the model is rather simple, it may be able to realize both the small and large mixing angle solutions for the solar neutrino problem. In particular, the large mixing angle MSW solution for the solar neutrino problem can be easily realized. We discuss the relation between the extra U(1)-charge and four solutions for the solar neutrino problem.

hep-ph↗

arXiv1999

Neutrino oscillations in a $3ν_L+3ν_R$ framework with five light neutrinos

We propose a neutrino mass matrix model in which five neutrino species remain light through the seesaw mechanism within a supersymmetric $3ν_L+3ν_R$ framework. We construct such a model based on the nonrenormalizable terms in the superpotential constrained by the discrete symmetry which may be expected in the models at the high energy scale such as superstring. We study the possible oscillation phenomena by fixing mass parameters so as to explain the solar and atmospheric neutrino deficits and also include a candidate of the suitable dark matter. We also discuss the charged lepton mass matrix based on this neutrino model. LSND results may be consistently explained within this model.

hep-ph↗