Observation of the isospin-violating decay $J/psi to phipi^{0}f_{0}(980)$

Using a sample of 1.31 billion $J/psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/psi to phi pi^{+}pi^{-}pi^{0}$ and $J/psi to phi pi^{0}pi^{0}pi^{0}$ are investigated. The isospin violating decay $J/psi to phi pi^{0} f_{0}(980)$ with $f_{0}(980) to pipi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/psi to phieta$, the branching fractions of $eta to pi^{+}pi^{-}pi^{0}$ and $eta to pi^{0}pi^{0}pi^{0}$, as well as their ratio, are also measured.

Observation of the electromagnetic doubly OZI-suppressed decay $J/psi rightarrow phi pi^{0}$

Using a sample of $1.31$ billion $J/psi$ events accumulated with the BESIII detector at the BEPCII collider, we report the observation of the decay $J/psi rightarrow phipi^{0}$, which is the first evidence for a doubly Okubo-Zweig-Iizuka suppressed electromagnetic $J/psi$ decay. A clear structure is observed in the $K^{+} K^{-}$ mass spectrum around 1.02 GeV/$c^2$, which can be attributed to interference between $J/psi rightarrow phipi^{0}$ and $J/psi rightarrow K^{+}K^{-}pi^{0}$ decays. Due to this interference, two possible solutions are found. The corresponding measured values of the branching fraction of $J/psi to phipi^{0}$ are $[2.94 pm 0.16text{(stat.)} pm 0.16text{(syst.)}] times 10^{-6}$ and $[1.24 pm 0.33text{(stat.)} pm 0.30text{(syst.)}] times 10^{-7}$.