Khuri-Treiman analysis of $J\mathrm{/}\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0$

We study the decay $J\mathrm{/}\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ within the framework of the Khuri-Treiman equations. We find that the BESIII experimental di-pion mass distribution in the $\rho (770)$-region is well reproduced with a once-subtracted $P$-wave amplitude. Furthermore, we show that $F$-wave contributions to the amplitude improve the description of the data in the $\pi \pi$ mass region around 1.5 GeV. We also present predictions for the $J\mathrm{/}\psi \to {\pi }^0{\gamma }^{\ast }$ transition form factor.