WILSON'S EXPANSION WITH POWER ACCURACY

Because of the infrared renormalons, it is difficult to get power accuracy in the traditional approach to the Wilson’s operator product expansion. Based on a new perturbative renormalization scheme for power-divergent operators, I propose a practical version of the OPE that allows to calculate power corrections to desired accuracy. The method is applied to the expansion of the vector-current correlation function in QCD vacuum, in which field theoretical status of the gluon condensate is discussed.