Higgs production and decay in models with extra singlets and doublets - Precise predictions forthe LHC

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The discovery of a Higgs particle at the LHC was a spectacular success of particle physics. As next step the properties of this particle have to be measured precisely and it must be investigated whether the new boson is the Higgs boson of the Standard Model. This requires to study extended models and to compare them to experimental data. An interesting class of extended models are those with additional Higgs singlets and doublets. These models are in accordance with precision tests and approach the Standard Model in the decoupling limit, i.e. if the masses of the extra Higgs bosons get large and the couplings are chosen appropriately. Moreover, they allow for a consistent description of additional physical Higgs bosons which are searched for at the LHC. Since the differences between the Standard Model and these extended models might be small, precise theoretical predictions including corrections of next-to-leading order are mandatory. The calculation of these corrections requires a consistent formulation of these theories in higher orders and, in particular, a renormalization.This project aims at the investigation of Standard Model extensions with additional Higgs singlets or doublets. We will, in particular, study models with one additional Higgs singlet or doublet. We will first define the complete renormalization procedure of these models and work out the renormalization explicitly at next-to-leading order. Then, the important Higgs production and decay processes will be evaluated including next-to-leading-order strong and electroweak corrections. Finally, the results will be implemented into existing Monte Carlo programs. The resulting codes will be made available to the experimental collaborations for data analysis.