Nonet Classification of Scalar/Isoscalar Resonances in the Mass Region   below 1900 MeV: Observation of the Lightest Scalar Glueball
  We summarize the results of the investigation of the $IJ^{PC}=00^{++}$ wave which is devoted to the search for the lightest scalar glueball. In the framework of the K-matrix formalism, the $q\bar q$-nonet classification of the scalar/isoscalar states is performed in the mass region below 1900 MeV basing on the following data: GAMS data for $\pi^-p\to\pi^0\pi^0n$, $\eta\eta n$, $\eta\eta'n$; CERN-M\"unich data for $\pi^-p\to\pi^+\pi^-n$; Crystal Barrel data for $p\bar p\to\pi^0\pi^0\pi^0$, $\pi^0\pi^0\eta$, $\pi^0\eta\eta$; BNL data for $\pi\pi\to K\overline K$. It is shown the existence of an extra state for $q\bar q$ classification: this state is a good candidate for the lightest scalar glueball. Analysis of the glueball/$q\bar q$ mixing shows that the glueball state has mainly dispersed over three real resonances: $f_0(1300)$, $f_0(1500)$ and $f_0(1530^{+90}_{-250})$. The broad resonance with complex mass $m=1530^{+90}_{-250}-i(560\pm 140)$ MeV is descendant of the pure glueball. The restored mass of the pure glueball is equal to 1695 MeV. This value agrees well with the results of lattice gluodynamics. 
A.V. Anisovich, V.V. Anisovich, Yu.D. Prokoshkin and A.V. Sarantsev