The role of f 0 ( 1710 ) in the ?ω threshold peak of J / Ψ → γ ? ω

摘要

We study the process J / Ψ → γ ? ω , measured by the BES experiment, where a neat peak close to the ?ω threshold is observed and is associated to a scalar meson resonance around 1800 MeV. We make the observation that a scalar resonance coupling to ?ω unavoidably couples strongly to K K ˉ , but no trace of a peak is seen in the K K ˉ spectrum of the J / Ψ → γ K K ˉ at this energy. This serves us to rule out the interpretation of the observed peak as a signal of a new resonance. After this is done, a thorough study is performed on the production of a pair of vector mesons and how its interaction leads necessarily to a peak in the J / Ψ → γ ? ω reaction close to the ?ω threshold, due to the dynamical generation of the f 0 ( 1710 ) resonance by the vector–vector interaction. We then show that both the shape obtained for the ?ω mass distribution, as well as the strength are naturally reproduced by this mechanism. The work also explains why the ?ω peak is observed in the BES experiment and not in other reactions, like B ± → K ± ? ω of Belle.