The glueball among the light scalar mesons

TL;DR

This paper investigates the light scalar mesons, especially the potential glueball among them, using model-independent scattering analysis to identify resonances and assess their nature.

Contribution

It provides a largely model-independent analysis of pi pi scattering, identifying scalar mesons and discussing the glueball hypothesis with new experimental proposals.

Findings

Identified f_0(980), f_0(1500), and broad f_0(600) as scalar resonances

f_0(1370) not observed at certain decay levels

Proposed further experimental tests for glueball identification

Abstract

The lightest gluonic meson is expected with J^{PC}=0^{++}, calculations in full QCD point towards a mass of around 1 GeV. The interpretation of the scalar meson spectrum is hindered as some states are rather broad. In a largely model-independent analysis of pi+ pi- \to pi+ pi-, pi0 pi0 scattering in the region 600-1800 MeV a unique solution for the isoscalar S-wave is obtained. The resonances f_0(980), f_0(1500) and the broad f_0(600) or ``sigma'' are clearly identified whereas f_0(1370) is not seen at the level B(f_0(1370)\to pi pi)\gtrsim 10%. Arguments for the broad state to be a glueball are recalled. We see no contradiction with the reported large B(sigma \to gamma gamma) and propose some further experimental tests.