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

Computation of Hydro-geomorphologic Changes in Two Basins of Northeastern Greece

This chapter presents a composite mathematical model aiming at continuous simulations of hydro-geomorphological processes at the basin scale. Continuous hydrologic simulations, as well as continuous simulations of soil and streambed erosion processes, are performed in two neighbouring basins in northeastern Greece: Kosynthos river basin (district of Xanthi, Thrace, northeastern Greece) and Nestos river basin (Macedonia-Thrace border, northeastern Greece). Both basins are mountainous and covered by forested and bushy areas in their greatest part. Kosynthos river basin extends to an area of 237 km2, whilst Nestos river basin is quite bigger, covering an area of approximately 840 km2. The characteristic of Nestos river basin is the presence of a dam at its northwestern boundary, which largely affects the discharge, as well as the sediment transport in Nestos River. The application of the model results in continuous hydrographs and sediment graphs at the outlets of the two basins. Fine temporal scales are used, providing this way a continuous assessment of water and sediment discharge. The statistic efficiency criteria utilized for the comparison between computed and measured values of water and sediment discharge at the basin outlet provide satisfactory results. Therefore, it is concluded that the continuous hydro-geomorphologic modelling can be successfully applied to Kosynthos and Nestos river basins

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