Instantons and Meson Correlators in QCD

Various QCD correlators are calculated in the instanton liquid model in zeromode approximation and $1\mathrm{/}{N}_c$ expansion. Previous works are extended by including dynamical quark loops. In contrast to the original “perturbative” $1\mathrm{/}{N}_c$ expansion not all quark loops are suppressed. In the flavor singlet meson correlators a chain of quark bubbles survives the $N_c\to \mathrm{\infty }$ limit causing a massive ${\eta }^{\mathrm{\prime }}$ 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.