The calculation of power corrections in the fixed-point gauge

Abstract

We propose a simple method of calculating nonperturbative power corrections in QCD. We use the fixed-point gauge (x-x/sub 0/)/sub ..mu../ A/sub ..mu../(x) = 0 which has the advantage that the potential A/sub ..mu../(x) is directly expressed in terms of the field strength tensor G/sub munu/(x) and its covariant derivatives. This makes it possible to specify a clear algorithm for selecting the coefficients of gauge-invariant structures in the polarization operators of various currents in the vacuum field. This method is used to calculate the coefficient of the structure /sub 0/ in the polarization operator of vector currents for heavy quarks. Our result coincides with previous calculations. We have also done an original calculation of the coefficients of the structure /sub 0/ for the baryon currents corresponding to the proton and the ..delta.. isobar. The predictions for the mass of the proton and the ..delta.. isobar obtained recently by B. L. Ioffe from a sum-rule analysis are found to be insensitive to the effect of these power corrections, which he had not taken into account.