Finite-energy QCD sum rules

Abstract

We derive finite-energy QCD sum rules, using the operator product expansion of the two-point correlation function at complex and spacelike values of the energy, and the experimental information on the spectral function along a limited energy range. The usual Laplace (Borel) sum rules are recovered in the limiting case in which the spectral function is assumed to be known along the whole timelike axis. We discuss in this framework the values of the quark and gluon condensates in the case of the ρ current contribution to the polarization function.