Quark-antiquark potential andQ2duality

A detailed study is made of $Q^2$ duality for the $b\overline{b}$ system and the hypothetical heavy $t\overline{t}$ system using several potentials which include the perturbative QCD results for short distances. It turns out that the QCD corrections are essential in order that the sum rule holds. The Coulomb-type correction should not be neglected, and the gluonic correction to the leptonic width is also important.