New data on the KK-bar threshold region and the nature of the f0(S*)

We combine new data on fo(S*) production in J/ψ and Ds decays with earlier information on central production and elastic ππ, KK-bar processes to make a fresh examination of the fo(S*) resonance. The key feature of our amplitude analysis is its strict enforcement of unitarity. This allows the good energy resolution of the new J/ψ → φππ(KK-bar) data to play its full role in delineating the fo(S*) resonance structure that experiment demands. This enables us to distinguish alternative resonance mechanisms that have been proposed: we conclude that fo(S*) is most probably not a KK-bar molecule, nor an amalgam of two resonances, but a conventional Breit-Wigner-like structure. In this preferred description, the fo(S*) has rather a narrow width (Γo ∼ 52 MeV) and comparable couplings to ππ and KKbar . Possible spectroscopic interpretations are considered. (Author)