Quark structure of pseudoscalar mesons

TL;DR

This paper reviews the understanding of pseudoscalar mesons' properties through their quark and gluon structures, focusing on eta-eta' mixing, using both low-energy Chiral Perturbation Theory and high-energy light-cone wave functions.

Contribution

It introduces process-independent eta-eta' mixing parameters and explores their relations across different theoretical frameworks and conventions.

Findings

Defined process-independent mixing parameters.

Analyzed relations between different mixing bases.

Discussed implications of mixing with other states like pi^0 and eta(c).

Abstract

I review to which extent the properties of pseudoscalar mesons can be understood in terms of the underlying quark (and eventually gluon) structure. Special emphasis is put on the progress in our understanding of eta-eta' mixing. Process-independent mixing parameters are defined, and relations between different bases and conventions are studied. Both, the low-energy description in the framework of Chiral Perturbation Theory and the high-energy application in terms of light-cone wave functions for partonic Fock states, are considered. A thorough discussion of theoretical and phenomenological consequences of the mixing approach will be given. Finally, I will discuss mixing with other states pi^0, eta(c), ...).