The glueball among the light scalar mesons

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.

arXiv commentContribution to HADRON07 (XII Int. Conf. on Hadron Spectroscopy - Frascati, Oct 8-13, 2007), reference added