Qcd aspects of heavy to light currents

Resum

In decay processes of B mesons de so-called "heavy to light currents" play an important role, for example in the determination of matrix elements of the CKM mixing matrix. The present Thesis investigates various aspects of the strong interaction of the quarks participating in the heavy to light currents. The theory of the strong interaction is Quantum Chromodynamics, which is treated in perturbation theory. After a short introduction to the relevant effective theories, which are derived from QCD, some new results are presented. First the asymptotic behaviour of the perturbative series is investigated, and the second result are proofs of factorization theorems which are used to separate the perturbative from the non-perturbative contributions. Finally, the symmtries of the effective field theories are used to find relations between the non-perturbative matrix elements involved in "heavy to light currents".