Leptonic constants of heavy quarkonia in a potential approach of nonrelativistic QCD

We consider a general scheme for calculating the leptonic constant of heavy quarkonium (Q) over barQ in the framework of nonrelativistic quantum chromodynamics operating as the effective theory of the nonrelativistic heavy quarks. We explore the approach of a static potential in QCD, which takes into account both the evolution of the effective charge in the three-loop approximation and the linearly increasing potential term that provides the quark confinement. The leptonic constants of the (b) over barb and (c) over barc systems are evaluated by making use of a two-loop anomalous dimension for the current of the nonrelativistic quarks, where a factor for the normalization of matrix elements is introduced in order to preserve the renormalization group invariance of the estimates.