The Physics of Instantons in the pseudoscalar and vector meson mixing

TL;DR

This paper explores how instantons in Quantum Chromodynamics influence the mixing of pseudoscalar and vector mesons, providing explanations for mass anomalies and mixing angle differences observed experimentally.

Contribution

It offers a theoretical analysis of instantons' role in meson mixing, highlighting their impact on meson mass spectra and mixing angles in QCD.

Findings

Instantons contribute to the high masses of η and η' mesons.

Instantons explain differences in pseudoscalar and vector meson mixing angles.

Theoretical insights align with experimental observations.

Abstract

When the theory of Quantum Chromodynamics was introduced, it was to explain the observed phenomena of quark confinement and scaling. It was then discovered that the emergence of instantons is an essential consequence of this theory. This led to unanticipated explanations not only for the anomalously high masses of the $\eta$ and the $\eta'$ particles, but also for the remarkable differences that had been observed in the mixing angles for the pseudoscalar mesons and the vector mesons.