arXiv subjects

Nobuhiro Maekawa

Publications and source records attributed to Nobuhiro Maekawa.

At least 55 records · Page 3Linked to original sources

arXiv2002

Supersymmetric SU(3)^3 unification with Anomalous U(1)_A Gauge Symmetry

We consider supersymmetric unification based on the gauge symmetry SU(3)_C\times SU(3)_L\times SU(3)_R supplemented by an anomalous U(1)_A gauge symmetry. Realistic fermion masses and mixings are realized, including large mixings in the neutrino sector. We also consider the supersymmetric flavor problem, gauge coupling unification and proton decay. The dominant proton decay mode is expected to be p-> e^+π^0 and the lifetime is estimated to be \sim 10^{34}-10^{35} years.

hep-ph↗

arXiv2002

The GUT? Neutrino bi-large mixing and proton decay

In this talk, we introduce a new scenario of grand unified theory (GUT) with anomalous $U(1)_A$ gauge symmetry, which can explain doublet-triplet splitting, quark and lepton masses and mixing angles. In neutrino sector, the scenario realizes LMA solution for solar neutrino problem and large $U_{e3}=O(0.1)$. Moreover, the scenario predicts that the main decay mode of proton is from dimension 6 operators and the lifetime of proton must be near the present limit. The realization of gauge coupling unification requires that the cutoff scale of the scenario must be around the usual GUT scale $Λ_G\sim 2\times 10^{16}$ GeV, which is smaller than the Planck scale. It may suggest the extra dimension in which gauge fields in visible sector do not propagate. This talk is based on the papers. [maekawa,maekawa2,maekawa3,BM,MY]

hep-ph↗

arXiv2001

E_6 Unification with Bi-Large Neutrino Mixing

A scenario of SO(10) grand unified theory (GUT) proposed by one of the authors is extended to E_6 unification. This gives realistic quark and lepton mass matrices. In neutrino sector, the model reproduces large mixing angle (LMA) MSW solution as well as large mixing angle for atmospheric neutrino anomaly. In this model, right-handed down quark and left-handed lepton of the first and second generation belong to a single multiplet 27. This causes natural suppression of flavor changing neutral current(FCNC).

hep-ph↗

arXiv2001

Gauge Coupling Unification with Anomalous U(1)_A Gauge Symmetry

Recently we proposed a natural scenario of grand unified theories with anomalous U(1)_A gauge symmetry, in which doublet-triplet splitting is realized in SO(10) unification using Dimopoulos-Wilczek mechanism and realistic quark and lepton mass matrices can be obtained in a simple way. The scenario has an additional remarkable feature that the symmetry breaking scale and the mass spectrum of super heavy particles are determined essentially by anomalous U(1)_A charges. Therefore once all the anomalous U(1)_A charges are fixed, the gauge coupling flows can be calculated. We examine several models in which the gauge coupling unification is realized. Examining the conditions for the coupling unification, we show that when all the fields except those of the minimal SUSY standard model become super-heavy, the unification scale generically becomes just below the usual GUT scale Λ_G\sim 2\times 10^{16} GeV and the cutoff scale becomes around Λ_G. Since the lower GUT scale leads to shorter life time of nucleon, the proton decay via dimension six operator p\to e^+π^0 can be seen in future experiment. On the other hand, the lower cutoff scale than the Planck scale may imply the existence of extra dimension in which only gravity modes can propagate.

hep-ph↗

arXiv2001

A Road to the Standard Grand Unified Theory

In this talk, we propose a GUT scenario in which doublet-triplet splitting is naturally realized in SO(10) unification using the Dimopoulos-Wilczek mechanism and the realistic mass matrices of quarks and leptons are obtained in a simple way. For the neutrino sector, bi-maximal neutrino mixing angles are realized. Moreover, the generic interaction is allowed, namely, all the terms which are allowed by the symmetry are included in the scenario. Therefore, once we fix the integer number charges of the anomalous U(1)_A symmetry, which plays an essential role in the scenario, all the scales, GUT breaking scale, mass scales of superheavy particles, are determined. The scenario can be extended into E_6 unification, in which a condition for suppression of flavor changing neutral current (FCNC) is automatically satisfied.

hep-ph↗

arXiv2001

A natural solution for the μproblem with anomalous U(1)_A gauge symmetry

Recently we proposed an attractive scenario of grand unified theories with anomalous $U(1)_A$ gauge symmetry, in which doublet-triplet splitting is naturally realized in SO(10) unification using Dimopoulos-Wilczek mechanism and realistic quark and lepton mass matrices can be obtained in a simple way. In this paper we show that there is a mechanism in which the doublet Higgs obtains the supersymmetric mass which is proportional to the SUSY breaking parameters. This mechanism can be applied easily in the above scenario. The point is that the mass term, which is forbidden by SUSY zero mechanism, can be induced by SUSY breaking. The proportional coefficient is controlled by the anomalous U(1)_A charges.

hep-ph↗

arXiv2001

Neutrino masses, anomalous U(1) gauge symmetry and doublet-triplet splitting

We propose an attractive scenario of grand unified theories in which doublet-triplet splitting is beautifully realized in SO(10) unification using Dimopoulos-Wilczek mechanism. The anomalous U(1)_A gauge symmetry plays essential roles in the doublet-triplet splitting mechanism. It is interesting that the anomalous U(1)_A charges determine the unification scale and mass spectrum of additional particles as well as the order of Yukawa couplings of quarks and leptons. For the neutrino sector, bi-maximal mixing angles are naturally obtained and proton decay via dimension 5 operators is suppressed. It is suggestive that the anomalous U(1)_A gauge symmetry motivated by superstring theory excellently solves the two biggest problems in grand unified theories, fermion mass hierarchy problem and doublet-triplet splitting problem.

hep-ph↗

arXiv2000

Vacuum Selection by Collapsing

In this talk, we discuss the possibility that the vacuum is dynamically determined in the history of the universe. The point is that some of the bubbles with a certain vacuum shrink by the evolution of the universe via gravity and may become black holes. It is interesting that in many cases false vacua are favored in the context of cosmology. By using this argument, supersymmetry(SUSY), if it exists, can be broken cosmologically. This talk is based on Ref.[1].

astro-ph↗

arXiv2000

Vacuum selection by recollapsing

We discuss the possibility that the vacuum is dynamically determined in the history of the universe. The point is that some of the bubbles with a certain vacuum shrink by the evolution of the universe via gravity and may become black holes. When the temperature of the phase transition T_{PT} is higher than 10^9 GeV, these black holes evaporate until now. If T_{PT}<10^9 GeV, we may see these black holes in our universe. It is interesting that in many cases false vacua are favored in the context of cosmology. By using this argument, supersymmetry(SUSY), if it exists, can be broken cosmologically. We can guess the SUSY breaking scale from the mass of the black holes.

hep-ph↗

arXiv1999

Anomalous U(1) Gauge Symmetry and Lepton Flavor Violation

In recent years, many people have studied the possibility that the anomalous U(1) gauge symmetry is a trigger of SUSY breaking and/or an origin of the fermion mass hierarchy. Though it is interesting that the anomalous U(1) symmetry may explain these two phenomena simultaneously, it causes a negative stop mass squared or a severe fine-tuning in order to avoid the FCNC problem. Recently, it was pointed out that the F-term contribution of the dilaton field can dominate the flavor-dependent contribution from the anomalous U(1) D-term, so that the FCNC problem may be naturally avoided. In this paper, we study the case in which the dilaton is stabilized by the deformation of the Kähler potential for the dilaton and find that the order of the ratio of the F-term to the D-term contributions is generally determined. This implies that the branching ratio of μ\to e γcan be found around the present experimental bound.

hep-ph↗

arXiv1997

Duality of a Supersymmetric Model with the Pati-Salam group

Recently one of the authors proposed a dual theory of a Supersymmetric Standard Model (SSM), in which it is naturally understood that at least one quark (the top quark) should be heavy, i.e., almost the same order as the weak scale, and the supersymmetric Higgs mass parameter $μ$ can naturally be expected to be small. However, the model cannot have Yukawa couplings of the lepton sector. In this paper, we examine a dual theory of a Supersymmetric Model with the Pati-Salam gauge group $SU(4)_{PS}\times SU(2)_L\times SU(2)_R $ with respect to the gauge group $SU(4)_{PS}$. In this scenario, Yukawa couplings of the lepton sector can be induced. In this model the Pati-Salam breaking scale should be around the SUSY breaking scale.

hep-ph↗

arXiv1997

Deformations of N=2 Dualities to N=1 Dualities in SU, SO and USp Gauge Theories

We study deformations of dualities in finite N=2 supersymmetric QCD. Adding mass terms for some quarks and the adjoint matter to the finite N=2 theory, which is known to have dual descriptions, the correspondence of gauge invariant operators between the original and dual theory is deformed. As a result, we naturally obtain N.Seiberg's N=1 duality. Furthermore, we discuss the origin of the meson and superpotential in the dual theory. This approach can be applied to SU(N), SO(N), and USp(2N) gauge theories, and we analyze all these cases.

hep-th↗

arXiv1995

Duality of a Supersymmetric Standard Model

We examine a dual theory of a Supersymmetric Standard Model(SSM) in terms of an $SU(3)_C$ gauge group. In this scenario, it is naturally understood that at least one quark (the top quark) should be heavy, i.e., almost the same order as the weak scale. Moreover, the supersymmetric Higgs mass parameter $μ$ can naturally be expected to be small. This model automatically induces nine pairs of composite Higgs fields, which may be observed in the near future.

hep-ph↗

arXiv1995

Duality of a Supersymmetric Standard Model without R parity

Recently one of the authors proposed a dual theory of a Supersymmetric Standard Model (SSM), in which it is naturally understood that at least one quark (the top quark) should be heavy, i.e., almost the same order as the weak scale, and the supersymmetric Higgs mass parameter $μ$ can naturally be expected to be small. Unfortunately, the model cannot possess Yukawa couplings of lepton sector. In this paper, we examine a dual theory of a Supersymmetric Standard Model without R parity. In this scenario, we can introduce Yukawa couplings of lepton sector. In order to induce the enough large Yukawa couplings of leptons, we must introduce fairly large R parity breaking terms, which may be observed in the near future.

hep-ph↗

arXiv1995

Vector-like Strong Coupling Theory with Small S and T Parameters

We discuss a mechanism which can reduce the S and T parameters in dynamical electroweak symmetry breaking scenario. It is interesting that not only T but also S parameters can be made small even if large isospin violation exists, which can realize the heavy top quark. The point is that if massive vector-like fermions, which have gauge invariant masses, can condense and break the electroweak symmetry, the S and T parameters can be small because of the decoupling theorem. Moreover, the model predicts a heavier Higgs boson, which may be found in LHC. The presentation basically follows the original papers.

hep-ph↗

arXiv1994

Vector-like Strong Coupling theory with small S and T parameters

We propose a mechanism which can reduce the Peskin and Takeuchi's S, T and U parameters in dynamical electroweak symmetry breaking models. It is interesting that not only S but also T parameter can become small even if there exists large isospin violation in fermion condensation. For example, when we take the $SU(2)_L\times U(1)_Y$ breaking mass of up-type fermion $m_U=1$ TeV and that of down-type $m_D=0$, we get S$\sim 0.001 N$ and T$\sim 0.05 N$ for the $SU(2)_L\times U(1)_Y$ invariant masses $M=10$ TeV. The point is that these parameters are suppressed by $SU(2)_L\times U(1)_Y$ invariant masses which the vector-like fermions can have.

hep-ph↗

arXiv1992

A Signal for Technicolor?

We propose an interpretation for the ($l\bar lγγ,\ M_{γγ}=60{\rm GeV}$) events, which have recently been reported by L3 group at LEP. This may be a first signal of `Technicolor' theory.

hep-ph↗

arXiv1992

Improving the Effective Potential

A general procedure is presented how to improve the effective potential by using the renormalization group equation (RGE) in MS bar scheme. If one knows the L-loop effective potential and the RGE coefficient functions up to (L+1)-loop level, this procedure gives an improved potential which satisfies the RGE and contains all of the leading, next-to-leading,... , and L-th-to-leading log terms.

hep-ph↗