Applications of QCD Sum Rules to Heavy Quark Physics

In these lectures, I present several important applications of QCD sum rules to the decay processes involving heavy-flavour hadrons. The first lecture is introductory. As a study case, the sum rules for decay constants of the heavy-light mesons are considered. They are relevant for the leptonic decays of $B$-mesons. In the second lecture I describe the method of QCD light-cone sum rules used to calculate the heavy-to-light form factors at large hadronic recoil, such as the $B\to \pi \ell \nu_\ell$ form factors. In the third lecture, the nonlocal hadronic amplitudes in the flavour-changing neutral current decays $B\to K^{(*)}\ell\ell$ are discussed. Light-cone sum rules provide important nonfactorizable contributions to these amplitudes.