19 research outputs found

### Invariants and CP violation in the 2HDM

We discuss the importance of basis invariants in the general 2HDM and how
these relates to masses and couplings. We also present a simple, yet powerful
technique to translate parameters of the potential into combinations of masses
and couplings of the theory and apply this to CP odd invariants.Comment: 14 pages. Talk given at Corfu Summer Institute 2017, School and
Workshops on Elementary Particle Physics and Gravity, September 2017. To
appear in conference proceeding

### The CP-symmetries of the 2HDM

We discuss the three different classes of CP-symmetries that can be realized
in a two-Higgs-doublet model, CP1, CP2 and CP3. We express conditions for
realizing these symmetries in terms of masses and couplings of the model,
thereby providing a way of verifying which, if any, of these symmetries is
realized by nature.Comment: Contribution to the conference proceedings of DISCRETE 1

### Heavy Higgs boson decays in the alignment limit of the 2HDM

The Standard Model (SM)-like couplings of the observed Higgs boson impose
strong constraints on the structure of any extended Higgs sector. We consider
the theoretical properties and the phenomenological implications of a generic
two Higgs doublet model (2HDM). This model constitutes a simple and attractive
extension of the SM that is consistent with the observation of the SM-like
Higgs boson and precision electroweak observables, while providing a potential
new source of CP-violation. In this paper we focus on the so-called Higgs
alignment limit of the generic 2HDM, where the neutral scalar field~$H_1$, with
the tree-level couplings of the SM Higgs boson, is a mass eigenstate that is
aligned in field space with the direction of the Higgs vacuum expectation
value. The properties of the two other heavier neutral Higgs scalars, $H_2$ and
$H_3$, in the alignment limit of the 2HDM are also elucidated. It is shown that
the couplings of $H_2$ and $H_3$ in the alignment limit are tightly constrained
and correlated. For example, in the exact alignment limit at tree level, for
bosonic final states $\text{BR}(H_{2,3} \to W^+W^-, ZZ, H_1 Z) = 0$ and
$\text{BR}(H^\pm \to W^\pm H_1) = 0$, whereas for fermionic final states
$\Gamma(H_2 \to f\bar f)/\Gamma(H_3 \to f\bar f) \sim M_2/M_3$ (where
$M_\alpha$ is the mass of $H_\alpha$). In some cases, the results of the
alignment limit differ depending on whether or not alignment is achieved via
the decoupling of heavy scalar states. In particular, in the exact alignment
limit without decoupling $\text{BR}(H_{2,3}\to H_1 H_1)=0$, whereas these
branching ratios are nonzero in the decoupling regime. Observables that could
be used to test the alignment scenario at the LHC are defined and discussed.
The couplings of the Higgs bosons away from their exact alignment values are
determined to leading order, and some consequences are elucidated.Comment: 44 pages, 1 figure; v2: references added; v3: major clarifications;
v4: JHEP versio

### 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.

### New Symmetries of the Two-Higgs-Doublet Model

The Two Higgs Doublet Model invariant under the gauge group SU(2)xU(1) is
known to have six additional global discrete or continuous symmetries of its
scalar sector. We have discovered regions of parameter space of the model which
are basis and renormalization group invariant to all orders of perturbation
theory in the scalar and gauge sectors, but correspond to none of the hitherto
considered symmetries. We therefore identify seven new symmetries of the model
and discuss their phenomenology. Soft symmetry breaking is required for some of
these models so that electroweak symmetry breaking can occur. We show that, at
least at the two-loop level, it is possible to extend some of these symmetries
to include fermions.Comment: 46 page

### 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