The decay η′ → ηπ 0 π 0 is studied in the framework of isobar model. It is shown, that good agreement with the experiment is achieved if α 0- and σ-meson contributions are taken into account. The contribution of α 0-meson is dominant, but σ-meson is necessary to reproduce the form of the Dalitz plot. Instead of the usual Breit-Wigner form of σ-meson propagator we use parametrization of the ππ-amplitude, which satisfies analyticity, crossing, unitarity and chirality constraints. This amplitude has a pole in the complex plane, which corresponds to σ-meson and describe experimental data on ππ-scattering in K e4 decay.
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