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The Decay Properties of the 1^{-+} Hybrid State

Within the framework of the QCD sum rules, we consider the three-point correlation function, work at the limit q^2 -> 0 and m_π-> 0, and pick out the singular term ~ {1\over q^2} to extract the pionic coupling constants of the 1^{-+} hybrid meson. Then we calculate the decay widths of different modes. The decay width of the S-wave modes b_1 π, f_1πincreases quickly as the hybrid meson mass and decay momentum increase. But for the low mass hybrid meson around 1.6 GeV, the P-wave decay mode ρπis very important and its width is around 180 MeV, while the widths of ηπand η^\prime πare strongly suppressed. We suggest the experimental search of π_1(1600) through the decay chains at BESIII: e^+e^- -> J/ψ(ψ') -> π_1 +γor e^+e^- -> J/ψ(ψ') -> π_1 +ρwhere the π_1 state can be reconstructed through the decay modes π_1 -> ρπ-> π^+π^-π^0 or π_1 -> f_1(1285)π^0. It is also interesting to look for π_1 using the available BELLE/BABAR data through the process e^+e^- -> γ^\ast -> ρπ_1, b_1π_1, γπ_1 etc.