Instantons and Meson Correlation Functions in QCD

Various QCD correlators are calculated in the instanton liquid model in zeromode approximation and 1/Nc expansion. Previous works are extended by including dynamical quark loops. In contrast to the original ”perturbative” 1/Nc expansion not all quark loops are suppressed. In the flavor singlet meson correlators a chain of quark bubbles survives the Nc →∞ limit causing a massive η′ in the pseudoscalar correlator while keeping massless pions in the triplet correlator. The correlators are plotted and meson masses and couplings are obtained from a spectral fit. They are compared to the values obtained from numerical studies of the instanton liquid and to experimental results.