Precision Study of $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ Decay Dynamics

TL;DR

This study provides a detailed analysis of the decay dynamics of eta prime to gamma pi+ pi- using a large data sample, revealing interference effects and contributions from resonances and anomalies with both model-dependent and independent methods.

Contribution

It is the first to observe omega and rho(770)-omega interference in eta prime decay and compares model-dependent and independent approaches for decay amplitude analysis.

Findings

Observation of omega and rho(770)-omega interference

Evidence for box anomaly or rho(1450) resonance contribution

Determination of decay amplitude components

Abstract

Using a low background data sample of $9.7\times10^{5}$ $J\psi\rightarrow\gamma\eta^\prime$, $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ 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 $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ are studied with both model-dependent and model-independent approaches. The contributions of $\omega$ and the $\rho(770)-\omega$ interference are observed for the first time in the decays $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ 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.