Lowest-Lying Scalar Mesons and a Possible Probe of Their Quark Substructure

TL;DR

This paper reviews the status of light scalar mesons below 1 GeV within a non-linear chiral Lagrangian framework, suggesting their quark substructure is likely closer to a four-quark configuration based on scattering data and mixing angles.

Contribution

It introduces a method to probe the quark substructure of light scalar mesons via scalar mixing angles within a non-linear chiral Lagrangian model, supported by experimental data.

Findings

Scalar nonet exists below 1 GeV.

Mixing angle suggests four-quark substructure.

Model consistent with pi pi, pi K scattering, and eta' decays.

Abstract

In this talk, an overview of the status of the light scalar mesons in the context of the non linear chiral Lagrangian of references [1-3] is presented. The evidence for the existence of a scalar nonet below 1 GeV is reviewed, and it is shown that by introducing a scalar nonet an indirect way of probing the quark substructure of these scalars through the scalar mixing angle can be obtained. It is then reviewed that consistency of this non-linear chiral Lagrangian framework with the experimental data on pi pi and pi K scattering, as well as the decay eta' to eta pi pi, results in a range for the mixing angle which indicates that the quark substructure of these light scalars are closer to a four quark picture.