Light scalar mesons in QCD sum rules with inclusion of instantons

TL;DR

This paper investigates light scalar mesons above 1 GeV using QCD sum rules, incorporating instanton effects to resolve degeneracy issues and explore the mesons' internal structure, including glueball contributions.

Contribution

The study introduces instanton effects into QCD sum rules to differentiate the masses of scalar mesons and analyze their internal structure, including glueball content.

Findings

Masses of scalar mesons are well separated with instanton effects.

Glueball content is significant in the structure of $f_{0}(1500)$.

Decay constants are also analyzed.

Abstract

The light scalar meson nonet above 1 GeV ({\it i.e.\}the $a_{0}$, $K^{\ast}_{0}$ and $f_{0}$) are studied within the framework of QCD sum rules. In conventional QCD sum rules, the calculated masses of this nonet are degenerate, and the mass of $K^{\ast}_{0}$ is always larger than the $a_{0}$ in contradiction with the observed spectrum. After improving the correlation function by including instanton effects, the masses are well separated from each other. In particular, our results shows glueball content plays an important role in the underlying structure of $f_{0}(1500)$. The decay constants are also discussed.