Searcharxiv⌕ Search

arXiv subjects

Naoyuki Haba

Publications and source records attributed to Naoyuki Haba.

At least 145 records · Page 8Linked to original sources
arXiv2003

Decoupling and lepton flavor violation in extra dimension

We discuss the fermion mass hierarchy and the flavor mixings in the fat brane scenario of five dimensional SUSY theory. The decoupling solution of the sfermion mass spectrum can be realized by introducing the vector-like mirror fields in an extra dimension. In this scenario, both the left- and right-handed sleptons can have sizable flavor mixings. We point out that this sizable flavor mixings can induce the suitable magnitude of the muon anomalous magnetic moment ($g_μ-2$) within the experimental bounds of lepton flavor violating processes.

hep-ph↗
arXiv2002

Fermion Mass Hierarchy and Supersymmetry Breaking in 6D SO(10) GUT on Orbifold

We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10) grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We introduce extra vector-like heavy fields in the extra dimensions, and the suitable fermion mass hierarchies and flavor mixings are generated by integrating out these heavy fields. We consider gaugino mediation and gauge mediation supersymmetry breaking mechanisms and their flavor structures. The experimental constraints of small flavor changing neutral currents suggest where to locate the supersymmetry breaking brane in the gaugino mediation mechanism. On the other hand, the SUSY breaking masses are highly degenerated in the gauge mediation scenario, where the flavor changing neutral currents are naturally suppressed as in the ordinal four dimensional gauge mediation models.

hep-ph↗
arXiv2002

A simple model of generating fermion mass hierarchy in N=1 supersymmetric 6D SO(10) GUT

We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10) grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We introduce 6D and 5D matter fields, which contains the 1st and 2nd generation matter fields as the zero modes, respectively. The 3rd generation matter fields are located on a 4D brane. The Yukawa couplings for bulk fields are suppressed by volume factors from extra dimensions. The suitable fermion mass hierarchies and flavor mixings are generated by the volume suppression factors.

hep-ph↗
arXiv2002

Neutrinoless double $β$ decay, neutrino mass hierarchy, and neutrino dark matter

Recently the evidence of the neutrinoless double $β$ ($0νββ$) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to inverted mass hierarchy (Type B) or degenerate mass (Type C) patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of $0νββ$ decay in the degenerate neutrinos including the cosmological constraint of neutrino dark matter, since the inverted mass hierarchy pattern always satisfies the cosmological constraint. The absolute value of neutrino mass is constrained by $0νββ$ experiment or cosmology depending on the relative signs (Majorana CP phases) of neutrino masses.

hep-ph↗
arXiv2002

(S)fermion Masses in Fat Brane Scenario

We discuss the fermion mass hierarchy and the flavor mixings in the fat brane scenario of a five dimensional SUSY theory. Assuming that the matter fields lives in the bulk, their zero mode wave functions are Gaussians, and Higgs fields are localized on the brane, we find simple various types of the matter configurations generating the mass matrices consistent with experimental data. Sfermion mass spectrum is also discussed using the matter configurations found above. Which type of squark mass spectra (the degeneracy, the decoupling and the alignment) is realized depends on the relative locations of SUSY breaking brane and the brane where Higgs fields are localized.

hep-ph↗
arXiv2002

Light Higgs Triplets in Extra Dimensions

We discuss the possibility that the Higgs triplet can be light (1TeV in the most interesting case) without contradictions with the proton stability %and the gauge coupling unification in the context of higher dimensional theory. The proton stability is ensured by the suppression of Yukawa coupling of the Higgs triplet to the matter through its small overlap of wave functions in extra dimensions. The light Higgs triplets might be detected in future collider experiments as an alternative signature of GUT instead of the proton decay. The gauge coupling unification can be preserved by introducing extra bulk matter fields.

hep-ph↗
arXiv2002

Decoupling Solution to SUSY Flavor Problem via Extra Dimensions

We discuss the decoupling solution to SUSY flavor problem in the fat brane scenario. We present a simple model to yield the decoupling sfermion spectrum in a five dimensional theory. Sfermion masses are generated by the overlap between the wave functions of the matter fields and the chiral superfields on the SUSY breaking brane. Two explicit examples of the spectrum are given.

hep-ph↗
arXiv2002

The neutrinoless double $β$ decay and the neutrino mass hierarchy

Recently the evidence of the neutrinoless double $β$ ($0νββ$) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to certain patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of $0νββ$ decay in the classification of the neutrino mass hierarchy patterns as Type A, $m_{1,2} \ll m_{3}$, Type B, $m_1 \sim m_2 \gg m_3$, and Type C, $m_1 \sim m_2 \sim m_3$, where $m_{i}$ is the $i$-th generation neutrino absolute mass. The data of $0νββ$ decay experiment suggests the neutrino mass hierarchy pattern should be Type B or C. Type B predicts a small magnitude of $0νββ$ decay which is just edge of the allowed region of experimental value in $95% \mathrm{c.l.}$, where Majorana CP phases should be in a certain parameter region. Type C can induce the suitably large amount of $0νββ$ decay which is consistent with the experimental data, where overall scale of degenerate neutrino mass plays a crucial role, and its large value can induce the large $0νββ$ decay in any parameter regions of Majorana CP phases.

hep-ph↗
arXiv2002

The stau exchange contribution to muon g-2 in the decoupling solution

We study the possibility that the lepton-flavor changing process can induce the suitable magnitude of the muon anomalous magnetic moment (g_μ-2) in the decoupling solution to the flavor problem in the minimal supersymmetric standard model. Our analyses introduce the flavor mixings of left- and right-handed stau and smuon phenomenologically. It is found that if both the left- and right-handed sleptons have sizable flavor mixings, the correction to g_μ-2 from the lighter slepton can reach to 10^{-9} while the correction to the branching ratio of τ\to μγsatisfies the current experimental bound. On the other hand, when only the left-handed or right-handed sleptons have the large flavor mixing, the suitable magnitude of the correction to g_μ-2 is not realized owing to the experimental bound of τ\to μγ.

hep-ph↗
arXiv2000

Anarchy and Hierarchy

We advocate a new approach to study models of fermion masses and mixings, namely anarchy proposed in hep-ph/9911341. In this approach, we scan the O(1) coefficients randomly. We argue that this is the correct approach when the fundamental theory is sufficiently complicated. Assuming there is no physical distinction among three generations of neutrinos, the probability distributions in MNS mixing angles can be predicted independent of the choice of the measure. This is because the mixing angles are distributed according to the Haar measure of the Lie groups whose elements diagonalize the mass matrices. The near-maximal mixings, as observed in the atmospheric neutrino data and as required in the LMA solution to the solar neutrino problem, are highly probable. A small hierarchy between the Delta m^2 for the atmospheric and the solar neutrinos is obtained very easily; the complex seesaw case gives a hierarchy of a factor of 20 as the most probable one, even though this conclusion is more measure-dependent. U_{e3} has to be just below the current limit from the CHOOZ experiment. The CP-violating parameter sin delta is preferred to be maximal. We present a simple SU(5)-like extension of anarchy to the charged-lepton and quark sectors which works well phenomenologically.

hep-ph↗
arXiv1998

The Singular Seesaw Mechanism with Hierarchical Dirac Neutrino Mass

The singular seesaw mechanism can naturally explain the atmospheric neutrino deficit by the maximal oscillation between $ν_{μ_L}$ and $ν_{μ_R}$. This mechanism can also induce three different scales of neutrino mass squared differences, which can explain the neutrino deficits of three independent experiments (solar, atmospheric, and LSND) by neutrino oscillations. In this paper we show that the realistic mixing angles among neutrinos can be obtained by introducing the hierarchy in the Dirac neutrino mass. In the case where Majorana neutrino mass matrix has rank 2, the solar neutrino deficit is explained by the vacuum oscillation between $ν_e$ and $ν_τ$. We also consider the case where Majorana neutrino mass matrix has rank 1. In this case, the mater enhanced Mikheyev-Smirnov-Wolfenstein solar neutrino solution is prefered as the solution of the solar neutrino deficit.

hep-ph↗
arXiv1998

The Sliding Singlet Mechanism with Gauge Mediated Supersymmetry Breaking

The sliding singlet mechanism is one of the most interesting solutions of the triplet-doublet splitting problem. We analyze this mechanism in the gauge mediated supersymmetry breaking scenario. We show that the sliding singlet mechanism does not work in the naive gauge mediation scenario because of the singlet linear terms derived from the gravity, although $F$ term is much smaller than the one in the gravity mediation scenario. We also consider the extension in order for the sliding singlet mechanism to work.

hep-ph↗
arXiv1998

Composite model with neutrino large mixing

We suggest a simple composite model that induces the large flavor mixing of neutrino in the supersymmetric theory. This model has only one hyper-color in addition to the standard gauge group, which makes composite states of preons. In this model, {\bf 10} and {\bf 1} representations in SU(5) grand unified theory are composite states and produce the mass hierarchy. This explains why the large mixing is realized in the lepton sector, while the small mixing is realized in the quark sector. This model can naturally solve the atmospheric neutrino problem. We can also solve the solar neutrino problem by improving the model.

hep-ph↗
arXiv1997

Model building in SUSY QCD

In N=1 Supersymmetric gauge theories, we can calculate non-perturbative effects in the superpotential. It is interesting to apply this effect to the phenomenology. We show two models here. One is the low energy supersymmetry (SUSY) breaking scenario without messenger sector, and the second is the composite model generating Yukawa interaction dynamically.

hep-ph↗
arXiv1996

Effective Messenger Sector from Dynamical Supersymmetry Breaking

In the framework of the dynamical supersymmetry breaking we construct the messenger sector as the effective theory of supersymmetry breaking sector, which is based on SU(3) \times SU(2) model of Affleck, Dine and Seiberg. In our model, messenger superfields with non-renormalizable interaction are contained. By minimizing the scalar potential, we show that the supersymmetry breaking can be communicated to the visible sector without breaking QCD color. In this model there appear various scales. Supersymmetry breaking scale turns out to be the intermediate scale ( \sim 10^{10} GeV ) between the GUT scale and the soft supersymmetry breaking scale.

hep-ph↗
arXiv1996

Spontaneous CP Violation and Higgs Masses in the Next-to-Minimal Supersymmetric Model

We study the possibility of spontaneous CP violation in the next-to-minimal supersymmetric standard model (NMSSM). It is shown that the spontaneous CP violation is induced by the radiative effects of top, stop, bottom and sbottom superfields. The available regions of parameters, which are obtained by imposing the constraints from experiments, are rather narrow. We also obtain strong constraints for light Higgs masses such as m_H \le 36 GeV numerically. Sum of masses of two light neutral Higgs should set around 93 GeV and charged Higgs boson has a rather higher mass larger than 700 GeV.

hep-ph↗