Amplitude Analysis of the Decays $\eta^\prime \rightarrow \pi^+\pi^-\pi^0$ and $\eta^\prime \rightarrow \pi^0\pi^0\pi^0$

Abstract

Based on a sample of 1.31×109 J/ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η′→π+π−π0 and η′→π0π0π0 is performed. A significant P-wave contribution from η′→ρ±π∓ is observed for the first time in η′→π+π−π0. The branching fraction is determined to be B(η′→ρ±π∓)=(7.44±0.60±1.26±1.84)×10−4, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S-wave component, there is a significant σ meson component. The branching fractions of the combined S-wave components are determined to be B(η′→π+π−π0)S=(37.63±0.77±2.22±4.48)×10−4 and B(η′→π0π0π0)=(35.22±0.82±2.54)×10−4, respectively. The latter one is consistent with previous BESIII measurements.