191 research outputs found
Diagnosing CP properties of the 2HDM
We have investigated a Two-Higgs-Doublet Model (2HDM), focusing on CP
violation. Various scenarios with spontaneous and explicit breaking of CP have
been considered. Some features of CP violation related to a choice of the basis
for the two Higgs doublets have been discussed and clarified. Regions in the
physical parameter space corresponding to spontaneous and explicit CP violation
have been located and discussed. The possibility to determine parameters of the
scalar potential with no reference to Yukawa couplings has been considered and
an unavoidable ambiguity has been found. The issue of disentangling spontaneous
and explicit CP violation has been investigated.Comment: 32 pages, 5 figures. Minor changes. Version to appear in JHE
Measuring CP violation in Two-Higgs-Doublet models in light of the LHC Higgs data
In Two-Higgs-Doublet models, the conditions for CP violation can be expressed
in terms of invariants under U(2) rotations among the two SU(2) Higgs doublet
fields. In order to design a strategy for measuring the invariants we express
them in terms of observables, i.e., masses and couplings of scalar bosons. We
find amplitudes directly sensitive to the invariants. Observation of the
Standard-Model-like Higgs boson at the LHC severely constrains the models. In
particular, in the model with Z_2 symmetry imposed on dimension-4 terms (in
order to eliminate tree-level flavour-changing neutral currents), CP violation
is strongly suppressed. On the other hand, the most general Two-Higgs-Doublet
model (without Z_2 symmetry) would still allow for CP violation to be present
in the model, without being in conflict with the LHC data. Consequently, also
flavour-changing neutral currents would in general be expected. We briefly
sketch a strategy for measuring the remaining CP violation.Comment: 26 pages, 7 figures. Version published in JHE
Testing the presence of CP violation in the 2HDM
We review CP properties of the Two-Higgs-Doublet model. In particular, we
show that spontaneous CP violation occurs in the parameter space on the border
between regions allowing explicit CP violation and those where there is another
minimum, deeper than the one corresponding to v=246 GeV. We discuss weak-basis
invariants which describe CP violation and express them through measurable
quantities like coupling constants and masses. Also, we discuss how CP
violation is constrained by the LHC Higgs data. Finally, we identify effective
operators that could be adopted to measure CP-invariants.Comment: 9 pages, Proceedings of the Corfu Summer Institute 2014 "School and
Workshops on Elementary Particle Physics and Gravity", 3-21 September 2014
Corfu, Greece. v2: References adde
A Simple Method to detect spontaneous CP Violation in multi-Higgs models
For models with several Higgs doublets we present an alternative method to
the one proposed by Branco, Gerard and Grimus, in 1984, to check whether or not
CP is spontaneously violated in the Higgs potential. The previous method is
powerful and rigorous. It requires the identification of a matrix
corresponding to a symmetry of the Lagrangian and verifying a simple relation
involving the vacuum expectation values. The nonexistence of such a matrix
signals spontaneous CP violation. However, as the number of Higgs doublets
increases, finding such a matrix may not be straightforward and it may turn
out to be easier to analyse the potential by going to the so-called Higgs
basis. The transformation to the Higgs basis is straightforward once the vacuum
expectation values are known. The method proposed in this work is also powerful
and rigorous and can be particularly useful to analyse models with more than
two Higgs doublets and with continuous symmetries.Comment: 9 pages, no figures. v2: minor changes, matching JHEP versio
Update on the CP-Violating Inert-Doublet Model
We have updated a recently proposed extension of the Inert Doublet Model. The
extension amounts to the addition of an extra non-inert scalar doublet. The
model thus offers a possibility of CP violation in the scalar sector and a
candidate for the Dark Matter. The recent XENON100 direct-detection experiment
excludes a considerable range of medium-low dark-matter masses, leaving only as
viable very low masses of order 5-10 GeV, as well as the regions from \sim 60
to \sim 110 GeV, and above \sim 530 GeV. For favorable parameter regions one
may observe related long-lived charged particles produced at the LHC.Comment: Contribution to PoS Proceedings, The XXth International Workshop High
Energy Physics and Quantum Field Theory, September 24 - October 1, 2011,
Sochi, Russi
Spontaneous symmetry breaking in the -symmetric scalar sector
We present a detailed study of the vacua of the -symmetric
three-Higgs-doublet potential, specifying the region of parameters where these
minimisation solutions occur. We work with a CP conserving scalar potential and
analyse the possible real and complex vacua with emphasis on the cases in which
the CP symmetry can be spontaneously broken. Results are presented both in the
reducible-representation framework of Derman, and in the
irreducible-representation framework. Mappings between these are given. Some of
these implementations can in principle accommodate dark matter and for that
purpose it is important to identify the residual symmetries of the potential
after spontaneous symmetry breakdown. We are also concerned with constraints
from vacuum stability.Comment: 37 pages. v2: Minor changes in the references, matches published
version. v3: Table 6 corrected: two additional cases conserve CP. Related
discussion adapted. Version consistent with JHEP Erratu
Symmetries and Mass Degeneracies in the Scalar Sector
We explore some aspects of models with two and three SU(2) scalar doublets
that lead to mass degeneracies among some of the physical scalars. In Higgs
sectors with two scalar doublets, the exact degeneracy of scalar masses,
without an artificial fine-tuning of the scalar potential parameters, is
possible only in the case of the inert doublet model (IDM), where the scalar
potential respects a global U(1) symmetry that is not broken by the vacuum. In
the case of three doublets, we introduce and analyze the replicated inert
doublet model, which possesses two inert doublets of scalars. We then
generalize this model to obtain a scalar potential, first proposed by Ivanov
and Silva, with a CP4 symmetry that guarantees the existence of pairwise
degenerate scalar states among two pairs of neutral scalars and two pairs of
charged scalars. Here, CP4 is a generalized CP symmetry with the property that
is the identity operator only for integer values that are
multiples of 4. The form of the CP4-symmetric scalar potential is simplest when
expressed in the Higgs basis, where the neutral scalar field vacuum expectation
value resides entirely in one of the scalar doublet fields. The symmetries of
the model permit a term in the scalar potential with a complex coefficient that
cannot be removed by any redefinition of the scalar fields within the class of
Higgs bases (in which case, we say that no real Higgs basis exists). A striking
feature of the CP4-symmetric model is that it preserves CP even in the absence
of a real Higgs basis, as illustrated by the cancellation of the contributions
to the CP violating form factors of the effective ZZZ and ZWW vertices.Comment: 52 pages, 2 figures, second revised version with new material, as
published by JHE
Implications of symmetries in the scalar sector
Symmetries play a very important r\^ole in Particle Physics. In extended
scalar sectors, the existence of symmetries may permit the models to comply
with the experimental constraints in a natural way, and at the same time reduce
the number of free parameters. There is a strong interplay among internal
symmetries of the scalar potential, its CP properties and mass degeneracies of
the physical scalars. Some of these aspects were discussed in this talk.Comment: 8 pages, to be published in the Proceedings of DISCRETE2018: 6th
Symposium on Prospects in the Physics of Discrete Symmetries, 26-30 Nov 2018.
Vienna, Austri
Spontaneous symmetry breaking in three-Higgs-doublet -symmetric models
The talk summarises work done by the authors consisting of a detailed study
of the possible vacua in models with three Higgs doublets with symmetry
and without explicit CP violation. Different vacua require special regions of
the parameter space which were analysed in our work. We establish the
possibility of spontaneous CP violation in this framework and we also show
which complex vacua conserve CP. In our work we discussed constraints from
vacuum stability. The results presented here are relevant for model building.Comment: 11 pages, no figures. Prepared for the proceedings of DISCRETE2016:
the Fifth Symposium on Prospects in the Physics of Discrete Symmetries, 28
November-3 December 2016, University of Warsaw, Poland, to appear in the
Journal of Physics: Conference Series (JPCS
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