New Aspects of Gauge-Boson Couplings and the Higgs Sector
The Standard Model will be probed at future linear e+ e- colliders for its validity at high energies and for its possible extensions. As an example we investigate Multi-Higgs-Doublet Models with respect to the stability of their potential and to spontaneous electroweak symmetry breaking. Further, two approaches to the model-independent parameterisation of new-physics effects in the gauge-boson sector are studied. In a form-factor approach to three-gauge-boson couplings at linear colliders in the process e+ e- ---> WW ---> 4 fermions the strongest possible bounds on the 28 parameters are determined by means of optimal observables. The improvement in sensitivity by longitudinal or transverse beam polarisation is analysed. One linear combination of couplings can be measured only with transverse polarisation. Formulae for the application of optimal observables in case of generic ambiguities in the reconstruction of final states are provided. In an effective-Lagrangian approach to the gauge-boson-Higgs sector ten dimension-six operators are added to the Lagrangian of the Standard Model. After electroweak symmetry breaking they contribute to gauge-boson self-couplings, gauge-boson-Higgs vertices and gauge-boson masses. Constraints from LEP observables on the anomalous parameters are derived. Effective three-gauge-boson couplings are defined such that the bounds from the form-factor approach can be translated to the effective-Lagrangian approach.
Networked Digital Library of Theses and Dissertations