Scalar mesons from an effective Lagrangian approach

TL;DR

This paper explores a generalized linear sigma model to understand light scalar mesons, predicting their quark content and mass spectrum, and showing improved agreement with experimental pion scattering data.

Contribution

It introduces a flavor-invariant model predicting four-quark content in light scalars and an exceptionally light singlet scalar, enhancing theoretical understanding of scalar mesons.

Findings

Light scalars have significant four-quark components.

One singlet scalar is predicted to be exceptionally light.

Model corrections improve agreement with pion scattering experiments.

Abstract

A brief discussion of the recent interest in light scalar mesons motivates the study of a generalized linear sigma model. In an SU(3) flavor invariant version of the model there is a prediction that the the lighter scalars have sizeable "four quark" content. It is further predicted that one of the singlet scalars should be exceptionally light. Due to the presence of scalar mesons, the model gives "controlled" corrections to the current algebra formula for threshold pion pion scattering. These corections act in the direction to improve agreement with current experiments.