124 research outputs found
Consistency of the Two Higgs Doublet Model and CP violation in top production at the LHC
It is important to provide guidance on whether CP violation may be measurable
in top-quark production at the Large Hadron Collider. The present work extends
an earlier analysis of the non-supersymmetric Two-Higgs-Doublet Model in this
respect, by allowing a more general potential. Also, a more comprehensive study
of theoretical and experimental constraints on the model is presented. Vacuum
stability, unitarity, direct searches and electroweak precision measurements
severely constrain the model. We explore, at low \tan\beta, the allowed regions
in the multidimensional parameter space that give a viable physical model. This
exploration is focused on the parameter space of the neutral sector rotation
matrix, which is closely related to the Yukawa couplings of interest. In most
of the remaining allowed regions, the model violates CP. We present a
quantitative discussion of a particular CP-violating observable. This would be
measurable in semileptonically decaying top and antitop quarks produced at the
LHC, provided the number of available events is of the order of a million.Comment: 45 pages, 10 figures, some in (essential) colour. Figures 2, 6 and 7
are bitmapped, better quality available on request. Version to appear in
Nucl. Phys.
Trilinear Higgs couplings in the two Higgs doublet model with CP violation
We carry out a detailed analysis of the general two Higgs doublet model with
CP violation. We describe two different parametrizations of this model, and
then study the Higgs boson masses and the trilinear Higgs couplings for these
two parametrizations. Within a rather general model, we find that the trilinear
Higgs couplings have a significant dependence on the details of the model, even
when the lightest Higgs boson mass is taken to be a fixed parameter. We include
radiative corrections in the one-loop effective potential approximation in our
analysis of the Higgs boson masses and the Higgs trilinear couplings. The
one-loop corrections to the trilinear couplings of the two Higgs doublet model
also depend significantly on the details of the model, and can be rather large.
We study quantitatively the trilinear Higgs couplings, and show that these
couplings are typically several times larger than the corresponding Standard
Model trilinear Higgs coupling in some regions of the parameter space. We also
briefly discuss the decoupling limit of the two Higgs doublet model.Comment: 23 pages, 15 figures. v2: References added, version to appear in PR
Natural Two-Higgs-Doublet Model
We show that the Two-Higgs-Doublet Model (2HDM) constrained by the
two-loop-order requirement of cancellation of quadratic divergences is
consistent with the existing experimental constraints. The model allows to
ameliorate the little hierarchy problem by suppressing the quadratic
corrections to scalar masses and lifting the mass of the lightest Higgs boson.
A strong source of CP violation emerges from the scalar potential. The cutoff
originating from the naturality arguments is shifted from 0.6 TeV in the
Standard Model to >6 TeV in the 2HDM, depending on the mass of the lightest
scalar.Comment: 2 figures, submitted to Fortschritte der Physik, presented at the
10th Hellenic School on Elementary Particle Physics and Gravity, Corfu 201
Constraining the Two-Higgs-Doublet-Model parameter space
We confront the Two-Higgs-Doublet Model with a variety of experimental
constraints as well as theoretical consistency conditions. The most
constraining data are the \bar B\to X_s\gamma decay rate (at low values of
M_{H^\pm}), and \Delta\rho (at both low and high M_{H^\pm}). We also take into
account the B\bar B oscillation rate and R_b, or the width \Gamma(Z\to b\bar b)
(both of which restrict the model at low values of \tan\beta), and the
B^-\to\tau\nu_\tau decay rate, which restricts the model at high \tan\beta and
low M_{H^\pm}. Furthermore, the LEP2 non-discovery of a light, neutral Higgs
boson is considered, as well as the muon anomalous magnetic moment. Since
perturbative unitarity excludes high values of \tan\beta, the model turns out
to be very constrained. We outline the remaining allowed regions in the
\tan\beta-M_{H^\pm} plane for different values of the masses of the two
lightest neutral Higgs bosons, and describe some of their properties.Comment: 17 pages, 17 figure
Pair Production of Two-Higgs-Doublet_Model Light Higgs Bosons in Collisions
We study the production of a pair of light, neutral, CP-even Higgs bosons in
photon--photon collisions within the general Two Higgs Doublet Model (THDM).
This is a process for which the lowest order contribution in both, the Standard
Model and the THDM, appears at one loop. We find that the cross section for
this process can be much larger in the THDM than in the Standard Model and the
number of events expected at the Photon Collider will allow a determination of
some of the parameters in the scalar potential.Comment: 10 pages, 4 figure
Probing the scalar-pseudoscalar mixing in the 125 GeV Higgs particle with current data
LHC has found hints for a Higgs particle of 125 GeV. We investigate the
possibility that such a particle is a mixture of scalar and pseudoscalar
states. For definiteness, we concentrate on a two Higgs doublet model with
explicit CP violation and soft Z2 violation. Including all Higgs production
mechanisms, we determine the current constraints obtained by comparing h ->
gamma gamma with h -> V V*, and comment on the information which can be gained
by measurements of h -> b \bar{b}. We find bounds |s_2| < 0.83 at one sigma,
where |s_2|=0 (|s_2|=1) corresponds to a pure scalar (pure pseudoscalar) state.Comment: 12 pages, 4 figure
Neutral Higgs-pair production at Linear Colliders within the general 2HDM: quantum effects and triple Higgs boson self-interactions
The pairwise production of neutral Higgs bosons is analyzed in the context of
the future linear colliders, such as the ILC and CLIC, within the general
Two-Higgs-Doublet Model (2HDM). The corresponding cross-sections are computed
at the one-loop level in full compliance with the current phenomenological
bounds and the stringent theoretical constraints inherent to the consistency of
the model. We uncover regions across the 2HDM parameter space, mainly for low
tan\beta near 1 and moderate values of the relevant lambda_5 parameter, wherein
the radiative corrections to the Higgs-pair production cross sections can
comfortably reach 50% This behavior can be traced back to the enhancement
capabilities of the trilinear Higgs self-interactions -- a trademark feature of
the 2HDM, with no counterpart in the Minimal Supersymmetric Standard Model.
Interestingly enough, the quantum effects are positive for energies around 500
GeV, thereby producing a significant enhancement in the expected number of
events precisely around the fiducial startup energy of the ILC. The Higgs-pair
production rates can be substantial, typically amounting to a few thousand
events per 500 inverse femtobarn of integrated luminosity. In contrast, the
corrections are negative in the highest energy range (1 TeV). We also compare
the exclusive pairwise production of Higgs bosons with the inclusive gauge
boson fusion channels leading to 2H+X finals states, and also with the
exclusive triple Higgs boson production. We find that these multiparticle final
states can be highly complementary in the overall Higgs bosons search strategy.Comment: 42 pages, 23 figures, 10 tables. Accepted in Phys. Rev. D (the
published version is shorter
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