Heavy meson decays are of significant importance for testing the Standard Model of particle physics. They provide possibilities to determine its parameters from experimental data and give hints to physics beyond the Standard Model. In order to exploit the provided data, a deep theoretical understanding of these decays is mandatory. The thesis is devoted to a thorough theoretical analysis of selected aspects of heavy meson flavor physics with the focus on the perturbative QCD effects.
The first part of the thesis is dedicated to the evaluation of leptonic decay constants. Decay constants constitute hadronic quantities, which parametrize transitions of a single meson to the QCD vacuum that are mediated by a local flavor current. They contain the only hadronic information in leptonic weak decays and enter as input parameters into the description of non-leptonic heavy meson decays and mixing processes. We apply the method of QCD sum rules to estimate the decay constants of vector and pseudoscalar heavy-light mesons in their ground state. This method includes the operator product expansion (OPE), which allows for a systematic implementation of perturbative corrections. We calculate perturbative QCD corrections to the leading term of the OPE with next-to-leading order accuracy. To this end, we construct a computation routine for one- and two-loop topologies and present the computational techniques in detail. The effects of SU(3)-flavor violation are also taken into account by including corrections of the strange quark mass. Our results gain highest precision within this approach by including all known perturbative contributions and new corrections to the quark-condensate contribution in the vector-meson channel for the first time.
In the second part we extend the QCD sum rule method, in which, in addition to the ground state contribution, excited states are also included. We present a statistical analysis to determine the decay constants of the first radially excited states of heavy-light mesons.
The final part of the thesis discusses inclusive weak decays of heavy hadrons. We apply the OPE within the heavy quark effective theory (HQET) to determine the total decay rate of such decays. We compute the radiative correction to the coefficient function of the power-suppressed chromomagnetic operator with next-to-leading accuracy. This correction is computed analytically and was up to now unknown. For this purpose, we perform a QCD-HQET-matching calculation and build a computational environment for on-shell two- and three-loop Feynman graphs. For phenomenological applications we also present moments of differential distributions. As a final statement, the influence on the CKM matrix entry |Vcb| due to the new correction term is estimated.