Study of η′→ηπ+π−η′→ηπ+π− Dalitz plot

The Dalitz plot of the η′→ηπ+π−η′→ηπ+π− decay is studied using the data collected with the VES spectrometer in two different exclusive reactions, π−p→η′nπ−p→η′n (charge-exchange) and π−N→η′π−Nπ−N→η′π−N (diffractive-like production). The η   mesons from η′η′ decays were detected in the η→γγη→γγ mode. The coefficients for the matrix element squared decomposition are measured on the largest statistics of η′η′ decays reported so far; there are ∼13.6×103∼13.6×103 and ∼6.5×103∼6.5×103 decays after background subtraction in charge-exchange and diffractive-like production, respectively.