A study of the ωη system produced in the reaction π−p → π+π−4γ n at 18 GeV/c Original Research Article

Results are presented on a study of structure in the ωη final state produced in π−p interactions at 18 GeV/c where ω → π+π−π0, π0 → 2γ, and η → 2γ. In the extended flux tube model, the ωη decay of an isoscalar JPC = 1−− hybrid meson is expected. The observed ωη invariant mass distribution rises rapidly from threshold but in general shows no obvious indication of resonant structure. However the result of a partial wave analysis finds both a JPC = 1−− signal consistent with the previously observed ω(1600) and a dominant JPC = 1+− partial wave which exhibits phase motion relative to the ω(1600). The decay ω(1600) → ωη has not been previously reported.