$0^{++}$ scalar glueball in finite-width Gaussian sum rules

TL;DR

This paper investigates the properties of the $0^{++}$ scalar glueball using Gaussian sum rules in QCD, incorporating instanton effects and finite resonance width to improve accuracy of decay width and coupling estimates.

Contribution

It introduces a finite-width Breit-Wigner spectral function into Gaussian sum rules for scalar glueballs, including instanton interactions, and validates the consistency of subtracted and unsubtracted sum rules.

Findings

Decay width and coupling constants for the scalar glueball are estimated.

Inclusion of instanton effects and finite width improves sum rule accuracy.

Consistency between different sum rule approaches is confirmed.

Abstract

Based on a semiclassical expansion for quantum chromodynamics in the instanton liquid background, the correlation function of the $0^{++}$ scalar glueball current is given, and the properties of the $0^{++}$ scalar glueball are studied in the framework of Gaussian sum rules. Besides the pure classical and quantum contributions, the contributions arising from the interactions between the classical instanton fields and quantum gluons are come into play. Instead of the usual zero-width approximation for the resonance, the Breit-Wigner form for the spectral function of the finite-width resonance is adopted. The family of the Gaussian sum rules for the scalar glueball in quantum chromodynamics with and without light quarks is studied. A consistency between the subtracted and unsubtracted sum rules is very well justified, and the values of the decay width and the coupling to the corresponding current for the $0^{++}$ resonance, in which the scalar glueball fraction is dominant, are obtained.