Scaling behaviour of leptonic decay constants for heavy quarkonia and heavy mesons

In the framework of QCD sum rules one uses a scheme, allowing one to apply the conditions of both nonrelativistic heavy quark motion inside mesons and independence of nonsplitting nS-state density on the heavy quark flavours. In the leading order an analitic expression is derived for leptonic constants of both heavy quarkonia and heavy mesons with a single heavy quark. The expression allows one explicitly to determine scaling properties of the constants. Introduction By definition, heavy quarks have the mQ mass values that are much greater than the confinement energy Λ. Therefore, in some cases, consideration of hadrons with the heavy quarks allows one to use expansions of some quantities over the small parameter of the Λ/mQ ratio. If the heavy quark virtualities inside a hadron are not large, then one allows the kinematical expansion pμQ = mQ · v μ + k , v · k ∼ 0 , (1) |k| ≪ mQ , where v is the quark 4-velocity, pQ is the quark momentum, k characterizes the heavy quark virtuality. In the kinematics of eq.(1) in QCD, the heavy quark action, expanded over the small parameter, leads to Effective Heavy Quark Theory (EHQT) [1], so, in the leading approximation the theory possesses the symmetry with respect to the substitution of a heavy quark,