12,967 research outputs found
Phenomenological discriminations of the Yukawa interactions in two-Higgs doublet models with symmetry
There are four types of two-Higgs doublet models under a discrete
symmetry imposed to avoid tree-level flavour-changing neutral current, i.e.
type-I, type-II, type-X and type-Y models. We investigate the possibility to
discriminate the four models in the light of the flavour physics data,
including mixing, , and
decays, the recent LHC Higgs data, the direct search
for charged Higgs at LEP, and the constraints from perturbative unitarity and
vacuum stability. After deriving the combined constraints on the Yukawa
interaction parameters, we have shown that the correlation between the mass
eigenstate rate asymmetry of and the
ratio could be sensitive probe to discriminate the four models with
future precise measurements of the observables in the
decay at LHCb.Comment: 29 pages, 4 tables, 11 figures. v3: minor corrections included,
matches published version in EPJ
The naturalness in the BLMSSM and B-LSSM
In order to interpret the Higgs mass and its decays more naturally, we hope
to intrude the BLMSSM and B-LSSM. In the both models, the right-handed neutrino
superfields are introduced to better explain the neutrino mass problems. In
addition, there are other superfields considered to make these models more
natural than MSSM. In this paper, the method of analyses will be
adopted in the BLMSSM and B-LSSM to calculate the Higgs mass, Higgs decays and
muon . With the fine-tuning in the region and ,
we can obtain the reasonable theoretical values that are in accordance with the
experimental results respectively in the BLMSSM and B-LSSM. Meanwhile, the
best-fitted benchmark points in the BLMSSM and B-LSSM will be acquired at
minimal and ,
respectively
The order analysis for the two loop corrections to lepton MDM
The experimental data of the magnetic dipole moment(MDM) of lepton(,
) is very exact. The deviation between the experimental data and the
standard model prediction maybe come from new physics contribution.
In the supersymmetric models, there are very many two loop diagrams
contributing to the lepton MDM. In supersymmetric models, we suppose two mass
scales and with for supersymmetric particles.
Squarks belong to and the other supersymmetric particles belong to
. We analyze the order of the contributions from the two loop diagrams. The
two loop triangle diagrams corresponding to the two loop self-energy diagram
satisfy Ward-identity, and their contributions possess particular factors. This
work can help to distinguish the important two loop diagrams giving corrections
to lepton MDM.Comment: 12 pages, 3 figure
Cosmological implications of modified gravity induced by quantum metric fluctuations
We investigate the cosmological implications of modified gravities induced by
the quantum fluctuations of the gravitational metric. If the metric can be
decomposed as the sum of the classical and of a fluctuating part, of quantum
origin, then the corresponding Einstein quantum gravity generates at the
classical level modified gravity models with a nonminimal coupling between
geometry and matter. As a first step in our study, after assuming that the
expectation value of the quantum correction can be generally expressed in terms
of an arbitrary second order tensor constructed from the metric and from the
thermodynamic quantities characterizing the matter content of the Universe, we
derive the (classical) gravitational field equations in their general form. We
analyze in detail the cosmological models obtained by assuming that the quantum
correction tensor is given by the coupling of a scalar field and of a scalar
function to the metric tensor, and by a term proportional to the matter
energy-momentum tensor. For each considered model we obtain the gravitational
field equations, and the generalized Friedmann equations for the case of a flat
homogeneous and isotropic geometry. In some of these models the divergence of
the matter energy-momentum tensor is non-zero, indicating a process of matter
creation, which corresponds to an irreversible energy flow from the
gravitational field to the matter fluid, and which is direct consequence of the
nonminimal curvature-matter coupling. The cosmological evolution equations of
these modified gravity models induced by the quantum fluctuations of the metric
are investigated in detail by using both analytical and numerical methods, and
it is shown that a large variety of cosmological models can be constructed,
which, depending on the numerical values of the model parameters, can exhibit
both accelerating and decelerating behaviors.Comment: 21 pages, 11 figures, accepted for publication in EPJ
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