Instantons in QCD (II). Correlators of pseudoscalar and scalar currents

We calculate the instanton-induced contributions to correlation functions in the QCD vacuum using numerical data on the ensemble of pseudoparticles (PPs) obtained previously. We show how quarks, "hopping" from one PP to another, do form the pseudoscalar mesons, with parameters close to the experimental ones. The hierarchy of the π, K, η, η′ masses are explained, as well as the sign and (approximately) the magnitude of the ηη′ mixing. All octet members have about the same coupling constants, while that for η′ seems to be larger by about 50%. Our results for the I = 1 scalar channel are consistent with the meson mass around 1 GeV and the coupling close to that of the pion.