Study of a near-threshold scalar resonance in the ωϕ system in pion-Be interaction at momentum of 29 GeV

The charge-exchange reaction π ^- Be→A ω (782)ϕ (1020) with ω→π ^+π ^-π ^0 and ϕ→ K^+K^- is studied with the upgraded VES facility (U-70, Protvino) using a 29 GeV pion beam. The distribution of the ωϕ invariant mass shows a near-threshold enhancement. Partial-wave analysis reveals that an isoscalar scalar state with J^PC=0^++ dominates in this mass region. Considering the observed signal as an f_0 resonance, and using the one-pion-exchange model, the product of the branching fractions into two channels Br(f_0→ππ ) Br(f_0→ωϕ ) is measured. Based on this value, a large partial width is found for the radiative decay of J/ψ into this state, which suggests a significant glueball component. The result is discussed under alternative assumptions concerning an identification of the observed signal as f_0(1710) or f_0(1770) .