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 BβΟβΞ½ββ form factors. In the third
lecture, the nonlocal hadronic amplitudes in the flavour-changing neutral
current decays BβK(β)ββ are discussed. Light-cone sum rules
provide important nonfactorizable contributions to these amplitudes.Comment: Lectures at the Helmholtz International Summer School "Physics of
Heavy Quarks and Hadrons'', July 2013, Dubna, Russia. SI-HEP-2013-1