PHYSICAL REVIEW LETTERS, cilt.120, sa.24, 2018 (SCI-Expanded)
Using a low background data sample of 9.7 x 10(5) J/psi -> gamma eta',eta' -> gamma pi(+)pi(-) events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of eta' -> gamma pi(+)pi(-) are studied with both model-dependent and model-independent approaches. The contributions of. and the rho(770)-omega interference are observed for the first time in the decays eta' -> gamma pi(+)pi(-) in both approaches. Additionally, a contribution from the box anomaly or the rho(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.