4,276 research outputs found
Spontaneous CP violation in the triplet extended supersymmetric standard model
We find that, at the one-loop level, the spontaneous CP violation is possible
in a supersymmetric standard model that has an extra chiral Higgs triplet with
hypercharge Y=0. At the tree level, this triplet-extended supersymmetric
standard model (TESSM) cannot have any reasonable parameter spaces for the
spontaneous CP violation, because the experimental constraints on the coupling
coefficient of the neutral Higgs boson to a pair of bosons exclude them. By
contrast, at the one-loop level, we find that there are experimentally allowed
parameter regions, where the spontaneous CP violation may take place. The mass
of the lightest neutral Higgs boson in the TESSM in this case may be as large
as about 100 GeV, by considering the one-loop contribution due to the top quark
and squark loops.Comment: 21 pages, 3 figure
Electroweak phase transition in the standard model with a dimension-six Higgs operator at one-loop level
The possibility of a strongly first-order electroweak phase transition by
means of a dimension-six Higgs operator in the Higgs potential of the standard
model is studied at finite temperature at the one-loop level. Exact calculation
of the one-loop effective Higgs potential at finite temperature suggests that
for the Higgs boson with its mass between 115 and 132 GeV the strongly
first-order electroweak phase transition is possible if a dimension-six
operator is present.Comment: 12 pages, 1 table, 4 figure
Electroweak phase transition and Higgs self-couplings in the two-Higgs-doublet model
We calculate both the cubic and the quartic self-couplings of the lighter
scalar Higgs boson without assuming the decoupling limit in the
two-Higgs-doublet model (THDM). In some regions of parameter space of the THDM
where the electroweak phase transition is strongly first order, it is possible
that the quartic self-coupling of the lighter scalar Higgs boson might be
deviated by at least 40 % from the standard model prediction.Comment: 5 pages, 1 figur
CP Violation in the Neutral Higgs Sector of a Non-minimal Supersymmetric Standard Model with Multiple Higgs Singlets
The possibility of CP violation is studied in the Higgs sector of a
supersymmetric standard model with multiple Higgs singlets. The tree-level
Lagrangian in this model is assumed to conserve the CP symmetry. We find that
CP violation is viable in this model at the one-loop level, in an explicit way,
if the radiative corrections from the third generation of quarks and squarks
are taken into account. In the presence of explicit CP violation, at the
one-loop level, the upper bound on the mass of the lightest neutral Higgs boson
and the productions of the neutral Higgs bosons via the Higgsstrahlung process
in high-energy collisions are calculated. We find that the upper bound
on the mass of the lightest neutral Higgs boson increases as the number of
Higgs singlets increases in a regulated manner. The production cross sections
of the neutral Higgs bosons also show a reasonable increasing behavior with
respect to the number of Higgs singlets.Comment: 21 pages, 4figures, JKP
Electroweak phase transition in an extension of the standard model with a real Higgs singlet
The Higgs potential of the standard model with an additional real Higgs
singlet is studied in order to examine if it may allow the strongly first order
electroweak phase transition. It is found that there are parameter values for
which this model at the one-loop level with finite temperature effect may allow
the desired phase transition. Those parameter values also predict that the
masses of the neutral scalar Higgs bosons of the model are consistent with the
present experimental bound, and that their productions in collisions
may be searched at the proposed ILC with = 500 GeV in the near
future.Comment: 25 pages, 12 figure
Radiative CP violation in the Higgs sector of the Next-to-minimal supersymmetric model
We investigate the neutral Higgs sector in the next-to-minimal supersymmetric
standard model (NMSSM) with explicit CP violation at the one-loop level by
using the effective potential method. In general, explicit CP violation is
possible at the tree-level in the Higgs potential of the NMSSM, which may
possess a complex phase. The tree-level Higgs potential can be made CP
conserving by assuming that all the relevant parameters are real. However, the
CP-conserving Higgs potential at the tree level may still develop complex
phases at the one-loop level through radiative corrections. These complex
phases exhibit explicit CP violation through the mixings between the scalar and
pseudoscalar Higgs bosons. One of the complex phases arise in the neutralino
sector. For a particular choice of the relevant parameter values, the
scalar-pseudoscalar mixings are found to strongly dependent on this phase.
Meanwhile, for a wide region in the parameter space, the ratios of CP mixing
elements of the neutral Higgs boson mass matrix to CP non-mixing ones increase
weakly against this phase. Also, the neutral Higgs boson masses are roughly
stable against the variation of this phase.Comment: Latex, 48 pages, 1 table, 17 figures, Changed conten
Possibility of spontaneous CP violation in Higgs physics beyond the minimal supersymmetric standard model
The Dine-Seiberg-Thomas model (DSTM) is the simplest version of the new
physics beyond the minimal supersymmetric standard model (MSSM), in the sense
that its Higgs sector has just two dimension-five operators, which are obtained
from the power series of the energy scale for the new physics in the effective
action analysis. We study the possibility of spontaneous CP violation in the
Higgs sector of the DSTM, which consists of two Higgs doublets. We find that
the CP violation may be triggered spontaneously by a complex phase, obtained as
the relative phase between the vacuum expectation values of the two Higgs
doublets. At the tree level, for a reasonably established parameter region, the
masses of the three neutral Higgs bosons and their corresponding coupling
coefficients to a pair of bosons in the DSTM are calculated such that the
results are inconsistent with the experimental constraint by the LEP data.
Thus, the LEP2 data exclude the possibility of spontaneous CP violation in the
DSTM at the tree level. On the other hand, we find that, for a wide area in the
parameter region, the CP symmetry may be broken spontaneously in the Higgs
sector of the DSTM at the one-loop level, where top quark and scalar top quark
loops are taken into account. The upper bound on the radiatively corrected mass
of the lightest neutral Higgs boson of the DSTM is about 87 GeV, in the
spontaneous CP violation scenario. We confirm that the LEP data does not
exclude this numerical result.Comment: 13 pages, 3 figures, PR
Electroweak baryogenesis in the MSSM with vector-like quarks
In the minimal supersymmetric standard model (MSSM), a strongly first-order
electroweak phase transition (EWPT) is only possible in a confined parameter
region where one of the scalar top quarks is lighter than the top quark and the
other one is as heavy as the SUSY breaking scale. If the MSSM is enlarged to
accommodate vector-like quarks and their superpartners, we find that the
strongly first-order EWPT is possible without requiring light scalar top quark
at the one-loop level, in the limit where the lightest scalar Higgs boson of
the MSSM behaves like the Higgs boson of the standard model and the other Higgs
bosons are all as heavy as the SUSY breaking scale. The strength of the
first-order EWPT is found to be dependent on the mass of the lightest neutral
Higgs boson and the mixing effects of the vector-like scalar quarks.Comment: 16 pages, 3 figures, 2 table
Higgs bosons of the NMSSM with explicit CP violation at the ILC
We study the Higgs sector of the next-to-minimal supersymmetric standard
model (NMSSM) with explicit CP violation at the one-loop level, where the
radiative corrections due to the quarks and squarks of the third generation are
taken into account. We expect that, within a reasonable region of the parameter
space of the present model, at least one of five neutral Higgs bosons may be
produced at the future International Linear Collider (ILC) with
GeV, with cross section larger than 12 fb, 15 fb, and 1.5 fb,
respectively, via the Higgs-strahlung process, the fusion process, and the
fusion process. We find that the effect of the CP phase in the present
model yields significant influences upon the production cross sections of the
five neutral Higgs bosons. We also study the decay modes of the five neutral
Higgs bosons to find that their decay widths are similarly affected by the CP
phase. Some of the decay modes in the present model behave differently from
those of the Standard Model.Comment: 36 pages, 18 figure
Study of Higgs self couplings of a supersymmetric model at the International Linear Collider
We study the Higgs self couplings of a supersymmetric model that has
two Higgs doublets and two Higgs singlets. The lightest scalar Higgs boson in
the model may be heavier than 112 GeV, at the one-loop level, where the
negative results for the Higgs search at the LEP2 experiments are taken into
account. The contributions from the top and scalar top quark loops are included
in the radiative corrections to the one-loop mass of the lightest scalar Higgs
boson, in the effective potential approximation. The effect of the Higgs self
couplings may be observed in the production of the lightest scalar Higgs bosons
in collisions at the International Linear Collider (ILC) via double
Higgs-strahlung process. For the center of mass energy of 500 GeV with the
integrated luminosity of 500 fb and the efficiency of 20 %, we expect
that at least 5 events of the lightest scalar Higgs boson may be produced at
the ILC via double Higgs-strahlung process.Comment: 21 pages, 5 figure
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