Precise predictions for neutralino and chargino pair production in supersymmetry

Supersymmetric theories like the Minimal Supersymmetric Standard Model (MSSM) predict the existence of partner particles to the well-established elementary particles. Among others are the so-called neutralinos and charginos, the superpartners of the gauge and Higgs bosons. If Supersymmetry (SUSY) is realized in nature, the SUSY-particles can be discovered at future collider experiments. In particular on a linear collider their properties can be determined at high precision. Therefore, this thesis deals in an extensive way with the calculation of observables in neutralino and chargino production in electron-positron annihilations within the MSSM. Emphasis is put on the determination of the corresponding one-loop radiative corrections, whose consideration is essential to obtain the required precision. The necessary calculation of hundreds of Feynman diagrams is performed by application of special algebraic software. However, one meets three problems: By integration of the (squared) Feynman-amplitudes over the free particle momenta, the so-called ultraviolet (UV), infrared (IR), and collinear divergences are introduced. These have to be treated by special techniques to obtain physically meaningful results. The UV-divergences can be removed within the scope of regularization and subsequent renormalization. The applied on-shell renormalization scheme is deduced in a consistent and detailed way. Particular importance is given to a unique definition of the 'soft' SUSY-breaking parameters. IR-divergences originate from the exchange of virtual photons. Meaningful observables are only obtained, if in addition to the loop-contributions also real photon emission is considered. In this connection, the mentioned collinear divergences arise, since photons are also radiated off collinearly to the incoming electron-positron beams. These are regularized by the finite electron mass. But due to the fact, that the mass is by many orders of magnitude smaller than the beam energy, the collinear photons yield large contributions to the radiative corrections. This leads to two difficulties: at one hand, the numerical problems need to be solved. Therefore, the contributions of collinear photons are separated from the numerical phase-space integration and further treated in an analytical way. On the other hand, it is necessary to take higher orders of these large collinear corrections into account, in order to obtain a result of adequate accuracy. Even if only the sum of all these components yields a reasonable observable, a physically motivated separation of the complete considered radiative corrections has its advantages and is therefore also discussed. (author)