Odd Magne Ogreid

The oblique parameters in multi-Higgs-doublet models

We present general expressions for the oblique parameters S, T, U, V, W, and X in the SU(2)×U(1) electroweak model with an arbitrary number of scalar SU(2) doublets, with hypercharge ±1/2, and an arbitrary number of scalar SU(2) singlets.

A precision constraint on multi-Higgs-doublet models

We derive a general expression for Δρ (or, equivalently, for the oblique parameter T) in the SU(2) × U(1) electroweak model with an arbitrary number of scalar SU(2) doublets, with hypercharge ±1/2, and an arbitrary number of scalar SU(2) singlets. The experimental bound on Δρ constitutes a strong constraint on the masses and mixings of the scalar particles in that model.

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 B{yields}X{sub s}{gamma} decay rate (at low values of M{sub H{sup {+-}}}), and {delta}{rho} (at both low and high M{sub H{sup {+-}}}). We also take into account the BB oscillation rate and R{sub b}, or the width {gamma}(Z{yields}bb) (both of which restrict the model at low values of tan{beta}), and the B{sup -}{yields}{tau}{nu}{sub {tau}} decay rate, which restricts the model at high tan{beta} and low M{sub H{sup {+-}}}. Furthermore, the LEP2 nondiscovery 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{sub H{sup {+-}}} plane for different values of the masses of the two lightest neutral-Higgs bosons, and describe some of their properties.

Consistency of the two-Higgs-doublet model and CP violation in top production at the LHC

Abstract 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 β , 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.

Natural Multi-Higgs Model with Dark Matter and CP Violation

We explore an extension of the inert doublet model which allows also for CP violation in the Higgs sector. This necessitates two noninert doublets. The lightest neutral scalar of the inert doublet is a candidate for dark matter. Scanning over parameters we preserve the abundance of the dark matter in agreement with the WMAP data. We also impose all relevant collider and theoretical constraints to determine the allowed parameter space for which both the dark matter is appropriate and CP is violated. In addition we find regions where the cutoff of the model originating from naturality arguments can be substantially lifted compared to its standard model value, reaching {approx}2-3 TeV.

Measuring CP violation in two-Higgs-doublet models in light of the LHC Higgs data

A bstractIn 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 ℤ2

Diagnosing CP properties of the 2HDM

{\mathbb{Z}}_2

More series related to the Euler series

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 ℤ2