Evaluation of multi-loop multi-scale integrals and phenomenological two-loop applications

In this thesis, major developments in the publicly available program SecDec are presented, extending the numerical evaluation of multi-loop multi-scale integrals from Euclidean to physical kinematics. The power of this new feature is shown in two phenomenological applications. In the first, numerical results for several massive two-loop four-point functions are shown. In its second application within this thesis, the leading momentum-dependent two-loop corrections to the neutral $\mathcal{CP}$-even MSSM Higgs-boson masses are calculated. The results are included in the code FeynHiggs.