TY  - GEN
Y1  - 2008///
ID  - heidok8597
N2  - Theories with extended Higgs sectors such as Two-Higgs-Doublet Models (THDMs) or the Next-to-Minimal Supersymmetric Standard Model (NMSSM) allow for rich CP phenomena and involved Higgs-potential structures. Employing a gauge invariant formulation for the tree-level Higgs potential of the general THDM, we derive compact criteria for its stability, electroweak symmetry breaking, and generalised CP properties in a clear geometrical language. A new type of CP symmetry is shown to impose strong restrictions on the Lagrangian and to require at least two fermion generations for non-trivial Yukawa terms. Large regions of the NMSSM parameter space are excluded due to an instable vacuum. We present a rigorous determination of the global minimum of the tree-level potential via Gröbner bases. In a second part, we investigate the colour dipole picture. This model of high energy photon-proton scattering permits a very successful description of available HERA data. Nevertheless, its range of applicability is limited. We derive general bounds on ratios of deep-inelastic proton structure functions within the colour dipole picture, following exclusively from its framework and photon wave function properties. Confronting these bounds with HERA data we can further restrict the range of applicability of the colour dipole picture. Finally, we calculate Ioffe times for a specific model and find them to be too small to justify the dipole picture at large photon virtualities. 
A1  - Manteuffel, Andreas von
TI  - Two Aspects of High Energy Physics : Methods for Extended Higgs Models and Constraints on the Colour Dipole Picture
AV  - public
KW  - THDM 
KW  -  NMSSM 
KW  -  Farbdipolmodell 
KW  -  Ioffe-ZeitenTHDM 
KW  -  NMSSM 
KW  -  colour dipole model 
KW  -  small-x 
KW  -  Ioffe times
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/8597/
ER  -