ИСТИНА

We propose a new method for calculating the dependences of the decay constants of heavy-light mesons on the light-quark mass mq based on QCD sum rules at infinitely large Borel mass parameter (local-duality limit). For a specific choice of the correlation functions, all condensate contributions vanish and the mq-dependence of the decay constants is shown to be mainly determined by the known analytic mq-dependence of the diagrams of perturbative QCD.