First observation of $\eta(1405)$ decays into $f_{0}(980)\pi^0$
  The decays $J/\psi \rightarrow \gamma \pi^+\pi^-\pi^0$ and $J/\psi \rightarrow \gamma \pi^0\pi^0\pi^0$ are analyzed using a sample of 225 million $\jpsi$ events collected with the BESIII detector. The decay of $\eta(1405)\ar f_{0}(980)\pi^0$ with a large isospin violation is observed for the first time. The width of the $f_{0}(980)$ observed in the dipion mass spectra is anomalously narrower than the world average. Decay rates for three-pion decays of the $\eta'$ are also measured precisely. 
BESIII Collaboration: M. Ablikim, M. N. Achasov, D. Alberto, D.J.   Ambrose, F. F. An, Q. An, Z. H. An, J. Z. Bai, R. B. F. ...
hep-ex