Pi- Eta Mixing from QCD Sum Rules

Abstract

The $q^2$ dependence of the $π$-$η$ mixing amplitude is examined with the use of QCD sum rules. The linear slope of the mixing function $θ(q^2)$ is found to be much smaller than that for $ρ$-$ω$ mixing. Thus the mixing amplitude is approximately the same in the space-like region as in the time-like one, and one may neglect the $q^2$ dependence of the mixing. A comparison between a hadron-meson, an effective chiral model, and the QCD sum rules approaches is made.