Study Of ηâ†'γπ~+Ï€~- Decay At Bes-â…¢

The interactions between and other particles have been attracted considerable attention since the discovery of meson in 1964. There is an anomalous interaction in the chiral perturbation theory describing the interactions among low-energy hadrons. The study of â†' +-decay mode can be used to test this anomalous interaction, especially box anomaly. At present,13 billion / events were accumulated at BESIII,which allows us to investigate â†' +-decay with an improved precision. WASY-at-COSY collaboration had preformed a study on the â†' +-decay, which was based on the energy distribution of photon. In this paper, we study such decay mode based on invariant mass distribution. Monte Carlo simulation is used to obtain detection efficiency and study backgrounds. Using bin by bin method, we got backgrounds subtracted +-mass spectrum. Two methods which are model-dependent and model-independent are applied to get parameters=-38.86(The parameter reflects the box anomaly) and =0.94380(coefficient of the first term of Taylor expansion) respectively.