U_A(1) Symmetry Breaking and eta, eta prime mesons in the Bethe-Salpeter Approach

TL;DR

This paper investigates U_A(1) symmetry breaking and the properties of eta and eta' mesons using the Bethe-Salpeter approach, incorporating flavor mixing and gluon interactions to compute meson masses and decay constants.

Contribution

It introduces a combined framework of Schwinger-Dyson and Bethe-Salpeter equations with flavor mixing to study meson properties, highlighting the weak flavor mixing interaction's role.

Findings

Pion mass is insensitive to flavor mixing strength.

Eta and eta' masses are reproduced with weak flavor mixing.

Flavor structures of eta and eta' depend on their masses.

Abstract

U_A(1) symmetry breaking is studied by introducing the flavor mixing interaction proposed by Kobayashi, Maskawa and 't Hooft. Combining the one gluon exchange interaction, the rainbow like Schwinger-Dyson equation and the ladder like Bethe-Salpeter equation are derived. The anomalous PCAC relation in the framework of this approximation is considered. The masses of the pseudoscalar mesons pi,eta and eta' are calculated. It is found that the pion mass is not sensitive to the strength of the flavor mixing interaction. On the other hand, the masses of eta and eta' are reproduced by a relatively weak flavor mixing interaction, for which the chiral symmetry breaking is dominantly induced by the soft-gluon exchange interaction. The decay constants are calculated and the anomalous PCAC relation is numerically checked. It is found that the flavor structures of the eta and eta' mesons significantly depend on their masses and therefore it is quetionable to define a flavor mixing angle for eta and eta'.