Mixing among lowest-lying scalar mesons and scalar glueball

TL;DR

This paper enhances the single nonet linear sigma model by including scalar glueball mixing, leading to better agreement with experimental data and identifying $f_0(1500)$ as predominantly a glueball state.

Contribution

The study introduces a new version of the SNLSM with scalar-glueball mixing based on scale symmetry, improving predictions of scalar meson properties and scattering behaviors.

Findings

$f_0(1500)$ is identified as a predominantly glueball state.

Model predictions for scalar meson masses and decay widths align with experimental data.

Improved $\pi ext{-} ext{N}$ scattering amplitude behavior matches observations better.

Abstract

Scalar glueball is implemented in single nonet linear sigma model (SNLSM) which basically includes lowest lying scalar and pseudoscalar mesons. Our new version of SNLSM involves mixing among scalar matter fields and glueball field which is enforced by scale symmetry considerations and the associated anomaly. Performing iterative Monte Carlo simulations, it is found that among the three candidates of scalar glueball, i.e., $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, only $f_0(1500)$ is predominately a glueball state with the mass prediction of $1.566 \pm 0.046$ GeV and the other two are predominately quarkonium. The $\pi\pi$, $\pi K$ and $\pi \eta$ scatterings are reinvestigated in the presence of scalar glueball and it is found that the overall behavior of the real part of the K-matrix unitarized $\pi \pi$ scattering amplitude is more compatible with observed data compared with the case of SNLSM without glueball. We have also presented the predictions of the model for the masses and decay widths of the scalars obtained from the poles of the K-matrix unitarized $\pi\pi$, $\pi K$ and $\pi \eta$ scattering amplitudes. Moreover the $\pi\pi$ scattering phase shift predicted by our model is compared with the prediction of generalized linear sigma model (GLSM) which contains two nonets of scalar mesons and two nonets of pseudoscalar mesons (a quark-antiquark nonet and a four-quark nonet). Despite the fact that at this stage our model lacks the second meson nonet above $1$ GeV, its prediction for the $\pi\pi$ scattering phase shift is close to the prediction of GLSM for $\sqrt{s}<1.1$ GeV and in better agreement with experimental data for $\sqrt{s}>1.1$ GeV in comparison with GLSM.