41 research outputs found
Constraints from Unrealistic Vacua in Supersymmetric Standard Model with Neutrino Mass Operators
We analyze a scalar potential of the minimal supersymmetric standard model
(MSSM) with neutrino mass operators along Unbounded-From-Below (UFB) and Color
and/or Charged Breaking (CCB) directions. We show necessary conditions to avoid
the potential minima which can be deeper than the realistic vacuum. These
conditions would constrain more strongly than conditions in the MSSM without
taking into account neutrino mass operators, and can improve the predictive
power of supersymmetric models with neutrino mass operators.Comment: 11 pages, 4 figure
Kaluza-Klein gluon and b-jet forward-backward asymmetry
The forward-backward asymmetry of -quark jets on the -pole measured at
LEP/SLD experiments shows us -2.8- deviation from the Standard Model
(SM) prediction. We examine a possibility of Kaluza-Klein (KK) gluon to explain
the \afbb data in a scenario based on the warped extra dimension model by
Randall and Sundrum. In this scenario, the KK gluon strongly couples to
-quark by an appropriate choice of the bulk quark mass terms. We find that
the \afbb data could be explained if the KK gluon mass is few hundred GeV.
Constraints on our scenario from the hadron collider experiments are discussed.Comment: 5 pages, 4 figures. Version to appear in Phys.Lett.
Light dark matter in NMSSM and implication on Higgs phenomenology
For the experimental search of neutralino dark matter, it is important to
know its allowed mass and scattering cross section with the nucleon. In order
to figure out how light a neutralino dark matter can be predicted in low energy
supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal
supersymmetric model), assuming all the relevant soft mass parameters to be
below TeV scale. We find that in the parameter space allowed by current
experiments the neutralino dark matter can be as light as a few GeV and its
scattering rate off the nucleon can reach the sensitivity of XENON100 and
CoGeNT. As a result, a sizable parameter space is excluded by the current
XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be
explained). The future 6000 kg-days exposure of XENON100 will further explore
(but cannot completely cover) the remained parameter space. Moreover, we find
that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson
must be present to satisfy the measured dark matter relic density.
Consequently, the SM-like Higgs boson may decay predominantly into a
pair of light Higgs bosons or a pair of neutralinos so that the conventional
decays like is much suppressed.Comment: Version in PLB (discussions added
Natural Islands for a 125 GeV Higgs in the scale-invariant NMSSM
We study whether a 125 GeV standard model-like Higgs boson can be
accommodated within the scale-invariant NMSSM in a way that is natural in all
respects, i.e., not only is the stop mass and hence its loop contribution to
Higgs mass of natural size, but we do not allow significant tuning of NMSSM
parameters as well. We pursue as much as possible an analytic approach which
gives clear insights on various ways to accommodate such a Higgs mass, while
conducting complementary numerical analyses. We consider both scenarios with
singlet-like state being heavier and lighter than SM-like Higgs. With A-terms
being small, we find for the NMSSM to be perturbative up to GUT scale, it is
not possible to get 125 GeV Higgs mass, which is true even if we tune
parameters of NMSSM. If we allow some of the couplings to become
non-perturbative below the GUT scale, then the non-tuned option implies that
the singlet self-coupling, kappa, is larger than the singlet-Higgs coupling,
lambda, which itself is order 1. This leads to a Landau pole for these
couplings close to the weak scale, in particular below ~10^4 TeV. In both the
perturbative and non-perturbative NMSSM, allowing large A_lambda, A_kappa gives
"more room" to accommodate a 125 GeV Higgs, but a tuning of these A-terms may
be needed. In our analysis we also conduct a careful study of the constraints
on the parameter space from requiring global stability of the desired vacuum
fitting a 125 GeV Higgs, which is complementary to existing literature. In
particular, as the singlet-Higgs coupling lambda increases, vacuum stability
becomes more serious of an issue.Comment: 34 pages, 4 figures, references added, minor corrections to text and
figures, version to be published in JHE
TeV scale mirage mediation in NMSSM
We study the next-to-minimal supersymmetric standard model. We consider soft
supersymmetry breaking parameters, which are induced by the mirage mediation
mechanism of supersymmetry breaking. We concentrate on the mirage mediation,
where the so-called mirage scale is the TeV scale. In this scenario, we can
realize the up-type Higgs soft mass of O(200) GeV, while other masses such as
gaugino masses and stop masses are heavy such as 1 TeV or more. Cancellation
between the effective \mu-term and the down-type Higgs soft mass ameliorates
the fine-tuning in the electroweak symmetry breaking even for \mu=O(500) GeV.
The mixing between the doublet and singlet Higgs bosons is suppressed by
(\lambda/\kappa)/tan\beta. Then the lightest doublet Higgs mass naturally
reaches 125 GeV lifted by the new quartic coupling. The higgsino and singlino
are light and their linear combination is the lightest superparticle.Comment: 24 pages, 24 figures, Numerical analysis is replaced with the version
calculated by NMSSMTools. Comments and references are added on the suppressed
doublet-singlet mixing and cases in which the 125 GeV boson is the 2nd
lightest CP-even scalar. The version accepted by JHE
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.Comment: 23 pages, 5 figure
Nanoporous ultra-high specific surface inorganic fibres
Nanoporous inorganic (silica) nanofibres with ultra-high specific surface have been fabricated by electrospinning the blend solutions of poly(vinyl alcohol) (PVA) and colloidal silica nanoparticles, followed by selective removal of the PVA component. The configurations of the composite and inorganic nanofibres were investigated by changing the average silica particle diameters and the concentrations of colloidal silica particles in polymer solutions. After the removal of PVA by calcination, the fibre shape of pure silica particle assembly was maintained. The nanoporous silica fibres were assembled as a porous membrane with a high surface roughness. From the results of Brunauer-Emmett-Teller (BET) measurements, the BET surface area of inorganic silica nanofibrous membranes was increased with the decrease of the particle diameters. The membrane composed of silica particles with diameters of 15 nm showed the largest BET surface area of 270.3 m(2) g(-1) and total pore volume of 0.66 cm(3) g(-1). The physical absorption of methylene blue dye molecules by nanoporous silica membranes was examined using UV-vis spectrometry. Additionally, the porous silica membranes modified with fluoroalkylsilane showed super-hydrophobicity due to their porous structures
Higgs Portal to Visible Supersymmetry Breaking
We propose a supersymmetric extension of the standard model whose Higgs
sector induces a spontaneous supersymmetry breaking by itself. Unlike the
minimal extension, the current Higgs mass bound can be evaded even at the
tree-level without the help of the soft breaking terms due to the usual hidden
sector, as is reminiscent of the next to minimal case. We also have a possibly
light pseudo-goldstino in our visible sector in addition to extra Higgs
particles, both of which stem from supersymmetry breaking dynamics. In such a
setup of visible supersymmetry breaking, we may see a part of supersymmetry
breaking dynamics rather directly in future experiments.Comment: 23 pages, 6 figures, references adde
Peccei-Quinn NMSSM in the light of 125 GeV Higgs
We study the phenomenology of the Peccei-Quinn invariant extension of the
next-to-minimal supersymmetric standard model (NMSSM) in view of the recent
discovery of a 125 GeV Higgs boson. The minimal model having no quadratic and
cubic terms of the NMSSM singlet field predicts a light singlino-like lightest
supersymmetric particle (LSP). The model is strongly constrained by the Higgs
invisible decay and the dark matter characteristic of the LSP, while some
constraints can be relaxed by assuming that the saxion, the CP-even companion
of the axion in the Peccei-Quinn sector, causes a late-time entropy production
diluting the thermal LSP density. The collider signal of the model contains
multi-jet and plus missing energy, which can be discovered in the early
stage of the 14 TeV LHC running.Comment: 40 pages, 10 figures, 6 tables. v3: references added, several
statements added and corrected, comments on the small tadpole soft term added
in sec. 2.