The lightest scalar glueball

Recently performed investigations of meson spectra allow us to determine the resonance structure for the waves IJPC=00⁺⁺, 10⁺⁺, 02⁺⁺, 12⁺⁺ = IJP= 1/2 0⁺ in the mass region up to 1900 MeV, thus establishing the meson multiplets 1³P₀q\ q and 2³P₀q\ q. Experimental data demonstrate that there are five scalar/isoscalar states in this mass region. Four of them are q\ q states, that is, members of the 1³P₀q\ q and 2³P₀q\ q nonets, while the fifth state is an extra one not accomodated by q \ q systematics; it has the properties of the lightest scalar glueball. Analysis of the 00⁺⁺-wave performed within the framework of the dispersion relation technique allows us to reconstruct the mixing of a pure gluonium with neighbouring scalar q \ q states belonging to 1³P₀q\ q and 2³P₀q\ q nonets: three scalar mesons share the gluonium state between each other -- those are two comparatively narrow resonances f₀(1300) and f₀(1500) and a broad resonance f₀(1530⁺⁹⁰₋₂₅₀). The broad state is a descendant of the gluonium, keeping about 40-50% of its component.