arXiv subjects

Norimi Yokozaki

Publications and source records attributed to Norimi Yokozaki.

At least 73 records · Page 4Linked to original sources

arXiv2013

Bino-Higgsino Mixed Dark Matter in a Focus Point Gaugino Mediation

We investigate the neutralino dark matter in the focus point gaugino mediation model with the O(100) GeV gravitino. The thermal relic abundance of the neutralino with a sizable Higgsino fraction can explain the dark matter density at the present universe. The spin-independent cross section is marginally consistent with the current upper limit from the XENON 100 experiment, and the whole parameter region can be covered at the XENON1T experiment. We also discuss the origin of the gluino mass to wino mass ratio at around 3/8, which is crucial for the mild fine-tuning in the electroweak symmetry breaking sector. It is shown that the existence of the non-anomalous discrete R-symmetry can fix this ratio to 3/8.

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arXiv2013

Focus Point in Gaugino Mediation ~ Reconsideration of the Fine-tuning Problem ~

We reconsider the fine-tuning problem in SUSY models, motivated by the recent observation of the relatively heavy Higgs boson and non-observation of the SUSY particles at the LHC. Based on this thought, we demonstrate a focus point-like behavior in a gaugino mediation model, and show that the fine-tuning is indeed reduced to about 2 percent level if the ratio of the gluino mass to wino mass is about 0.4 at the GUT scale. We show that such a mass ratio may arise naturally in a product group unification model without the doublet-triplet splitting problem. This fact suggests that the fine-tuning problem crucially depends on the physics at the high energy scale.

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arXiv2013

Higgs Boson Mass in Low Energy SUSY Models with Vector-like Matters

We show that the gauge mediation models with vector-like matters can explain the Higgs boson mass of 126 GeV without large soft scalar masses nor a large left-right mixing of the stops. The scenario has interesting features: the existence of the light non-colored SUSY particles accessible at the LHC and ILC, the explanation of the muon g-2 and the possibility of the enhanced di-photon decay rate of the Higgs boson.

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arXiv2013

Recent Result of the AMS-02 Experiment and Decaying Gravitino Dark Matter in Gauge Mediation

The AMS-02 collaboration has recently reported an excess of cosmic-ray positron fractions, which is consistent with previous results at PAMELA and Fermi-LAT experiments. The result indicates the existence of new physics phenomena to provide the origin of the energetic cosmic-ray positron. We pursue the possibility that the enhancement of the positron fraction is due to the decay of gravitino dark matter. We discuss that such a scenario viably fits into the models in which the soft SUSY breaking parameters are dominantly from gauge-mediation mechanism with superparticle masses of around 10 TeV. Our scenario is compatible with ~126 GeV Higgs boson, negative searches for SUSY particles, and non-observation of anomalous FCNC processes. We also point out that the scenario will be tested in near future by measuring the electric dipole moment of the electron and the lepton flavor violating decay of the muon.

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arXiv2013

Muon g-2 and 125 GeV Higgs in Split-Family Supersymmetry

We discuss the minimal supersymmetric standard model with "split-family" spectrum where the sfermions in the first two generations are in the hundreds GeV to a TeV range while the sfermions in the third generation are in the range of tens TeV. With the split-family spectrum, the deviation of the muon g-2 and the observed Higgs boson mass are explained simultaneously. It is predicted that the gluino and the squarks in the first two generations are within the reach of the LHC experiments in most favored parameter space for the universal gaugino mass, which can be tested by searching for events with missing transverse energy or events with stable charged massive particles. We also point out that the split-family scenario can be consistent with the focus point scenario for the non-universal gaugino masses where the required mu-term is in the hundreds GeV range.

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arXiv2013

Heavy Squarks and Light Sleptons in Gauge Mediation ~From the viewpoint of 125 GeV Higgs Boson and Muon g-2~

In the framework of gauge mediation models, we investigate scenarios with heavy squarks and light sleptons, motivated by the recent discovery of the Higgs boson and the deviation of the muon anomalous magnetic moment (g-2) from the SM prediction. We show that only models with a messenger multiplet in the adjoint representation of SU(5) GUT gauge group are the unique possibility that sleptons are light enough to explain the muon g-2 in the minimal setup. We also show that, if there is an additional source of the Higgs soft masses, the muon g-2 can be explained with messenger multiples in the fundamental representation of SU(5) with the help of the light higgsino. Some phenomenological aspects of these models are also discussed.

hep-ph↗

arXiv2013

Enhanced Diphoton Signal of the Higgs Boson and the Muon g-2 in Gauge Mediation Models

We study the diphoton signal of the Higgs boson in gauge mediated supersymmetry breaking models, which can explain both the Higgs boson mass of around 125 GeV and the result of the muon g-2 experiment. We consider two possible extensions of gauge mediation models: inclusion of vector-like matters, and a mixing between a messenger and the up-type Higgs. The large left-right mixing of staus is induced in both scenarios, resulting in the enhanced diphoton signal. We include a constraint from a charge breaking minimum, which is severe for the large left-right mixing of staus. The branching fraction of h to gamma gamma can be about 40 percent larger than that of the Standard Model Higgs boson, in the region of parameter space where the Higgs boson mass of around 125 GeV and the muon g-2 are explained.

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arXiv2012

Gauge Mediation Models with Vectorlike Matters at the LHC

Gauge mediation model with vectorlike matters (V-GMSB) is one of the few viable SUSY models that explains the 126 GeV Higgs boson mass and the muon anomalous magnetic moment simultaneously. We explore exclusion bounds on V-GMSB model from latest LHC SUSY searches.

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arXiv2012

Enhanced Higgs Mass in a Gaugino Mediation Model without the Polonyi Problem

We consider a SUSY breaking scenario without the Polonyi problem. To solve the problem, the enhanced couplings of the Polonyi field to an inflaton, gauge kinetic functions and itself are assumed. As a result, a gaugino mediated SUSY breaking occurs. In this scenario, the Higgs boson mass becomes consistent with the recently observed value of the Higgs-like boson (i.e., m_h ~= 125 GeV) for the gluino mass about 4TeV, which is, however, out of the reach of the LHC experiment. We show that the trilinear coupling of the scalar top is automatically enhanced by the presence of the extra matters. With such extra matters, the Higgs mass as large as 125 GeV can be realized with the gluino mass of 1-2 TeV which is within the reach of the LHC experiment. In our scenario, the gravitino is the lightest SUSY particle and the candidate for dark matter, and the Wino, Bino, and sleptons are in a range from 200 GeV to 700 GeV.

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arXiv2012

Peccei-Quinn extended gauge-mediation model with vector-like matter

We construct a gauge-mediated SUSY breaking model with vector-like matters combined with the Peccei-Quinn mechanism to solve the strong CP problem. The Peccei-Quinn symmetry plays an essential role for generating sizable masses for the vector-like matters and the $μ$-term without introducing dangerous CP angle. The model naturally explains both the 125GeV Higgs mass and the muon anomalous magnetic moment. The stabilization of the Peccei-Quinn scalar and the cosmology of the saxion and axino are also discussed.

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arXiv2012

A Solution to the mu/Bmu Problem in Gauge Mediation with Hidden Gauge Symmetry

We propose a solution to the mu/Bmu problem in gauge-mediated SUSY breaking, which does not suffer from the SUSY CP problem and is consistent with the solution to the strong CP problem. The model is based on Z_3-invariant NMSSM with additional vector-like matter charged under a hidden gauge group as well as the standard model gauge groups. The dynamical scale of the hidden gauge symmetry is set to be around 10 GeV. We show that this simple extension of the NMSSM resolves the domain wall problem and the mu/Bmu problem without a dangerous CP angle. The relative sign among gaugino masses and the mu parameter can be preferable in terms of the muon anomalous magnetic moment. We also discuss cosmological issues of this model, especially the effects of long-lived particles in the hidden gauge sector. The hidden glueball may cause a late-time entropy production, which opens up a possibility that the light gravitino can be a dominant component of dark matter while leptogenesis scenarios work successfully. There is a region where the electroweak symmetry is successfully broken with ~10 TeV stops, and the Higgs mass of ~125 GeV can be explained.

hep-ph↗

arXiv2012

Higgs Boson Mass in Low Scale Gauge Mediation Models

We consider low scale gauge mediation models with a very light gravitino m_{3/2}~16 eV, in the light of recent experimental hints on the Higgs boson mass. The light gravitino is very interesting since there is no gravitino over-production problem, but it seems difficult to explain the Higgs boson mass of ~125 GeV. This is because of the conflict between the light gravitino mass and heavy SUSY particle masses needed for producing the relatively heavy Higgs boson mass. We consider two possible extensions in this paper: a singlet extension of the Higgs sector, and strongly coupled gauge mediation. We show that there is a large parameter space, in both scenarios, where the Higgs boson mass of ~125 GeV is explained without any conflict with such a very light gravitino.

hep-ph↗

arXiv2012

Natural Supersymmetry and b -> s gamma constraints

We investigate constraints from the observed branching ratio for b -> s gamma and fine-tuning in the framework of natural supersymmetry. The natural supersymmetry requires the large trilinear coupling of the stop sector, light higgsinos (a small mu parameter) and light stops, in order to reduce the fine-tuning in the Higgs sector while avoiding the LEP constraint. It is found that in such a scenario 5% (10%) level of fine-tuning is inevitable due to the b -> s gamma constraint even if the messenger scale is as low as 10^5 GeV (10^4 GeV), provided that the gaugino masses satisfy the GUT relation.

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arXiv2012

Vacuum Stability Bound on Extended GMSB Models

Extensions of GMSB models were explored to explain the recent reports of the Higgs boson mass around 124-126 GeV. Some models predict a large mu term, which can spoil the vacuum stability of the universe. We study two GMSB extensions: i) the model with a large trilinear coupling of the top squark, and ii) that with extra vector-like matters. In both models, the vacuum stability condition provides upper bounds on the gluino mass if combined with the muon g-2. The whole parameter region is expected to be covered by LHC at sqrt{s} = 14 TeV. The analysis is also applied to the mSUGRA models with the vector-like matters.

hep-ph↗

arXiv2012

Higgs mass and muon anomalous magnetic moment in the U(1) extended MSSM

We study phenomenological aspects of the MSSM with extra U(1) gauge symmetry. We find that the lightest Higgs boson mass can be increased up to 125 GeV, without introducing a large SUSY scale or large A-terms, in the frameworks of the CMSSM and gauge mediated SUSY breaking (GMSB) models. This scenario can simultaneously explain the discrepancy of the muon anomalous magnetic moment (muon g-2) at the 1 sigma level, in both of the frameworks, U(1)-extended CMSSM/GMSB models. In the CMSSM case, the dark matter abundance can also be explained.

hep-ph↗

arXiv2012

NMSSM in gauge-mediated SUSY breaking without domain wall problem

A problem of the gauge-mediated SUSY breaking model is its difficulty to generate a natural value of mu/Bmu, while the NMSSM is a natural framework to solve the mu/Bmu problem. The NMSSM in gauge-mediated SUSY breaking in its original form does not work well since the singlet field cannot develop a desired vacuum expectation value. It also suffers from the cosmological domain wall problem. We study an extension of the model to include additional vector-like matter, which is charged under the hidden QCD. It is shown that this simple extension solves both the problems. We study phenomenological and cosmological implications of this extended models. The lightest Higgs mass can be as large as 130-140 GeV for some model points.

hep-ph↗

arXiv2011

Higgs mass, muon g-2, and LHC prospects in gauge mediation models with vector-like matters

Recently the ATLAS and CMS collaborations presented preliminary results of Standard Model Higgs searches and reported excesses of events for a Higgs boson at 124-126 GeV. Such a Higgs mass can be naturally realized, simultaneously explaining the muon g-2 anomaly, in gauge-mediated SUSY breaking models with extra vector-like matters. Upper bounds are obtained on the gluino mass, m_{\tilde g}\lesssim 1.2 (1.8) TeV, and on the extra vector-like quark mass, M_{Q'} \lesssim 1.0 (1.8) GeV, in the parameter region where the Higgs boson mass is 124-126 GeV and the muon g-2 is consistent with the experimental value at the 1 sigma (2 sigma) level. The LHC prospects are explored in the parameter region. It is found that some of the regions are already excluded by the LHC, and most of the parameter space is expected to be covered at \sqrt{s} = 14 TeV. A study on the extra vector-like quarks, especially current bounds on their masses and prospects for future searches, is also included.

hep-ph↗

arXiv2011

Relaxing the Higgs mass bound in singlet extensions of the MSSM

We show that the upper bound on the lightest Higgs mass in the MSSM is relaxed by introducing a singlet which couples to the Higgs fields, even at a large tan beta region, preferable for explaining the muon anomalous magnetic moment. In the models of a singlet extension, it is known that the upper bound is relaxed by a tree-level contribution, especially at small tan beta region. For large tan beta, however, the requirement for the perturbativity on the singlet-Higgs coupling up to the GUT scale prevents the lightest Higgs from obtaining a large tree-level mass. We construct an explicit UV complete model which allows large singlet-Higgs coupling at low energy without disturbing the perturbativity. The UV completion can be applied for any singlet extension of the MSSM. Moreover, we point out that the radiative correction from the singlet-Higgs coupling becomes dominant, and the lightest Higgs mass can be easily as heavy as 130 GeV if this coupling is large enough even for large tan beta.

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