**η / η ′ decays at BESIII**

*I. Garzia, On behalf of the BESIII collaboration*

in XXV International Workshop on Deep-Inelastic Scattering and Related Subjects

Contribution: pdf

**Abstract**

Decays of both $\eta$ and $\eta'$ mesons provide an unique laboratory to study and understand low-energy QCD, and search for physics beyond the Standard Model. We present the latest $\eta$ and $\eta'$ related results, which are obtained using $1.3\times 10^{8}$ \jpsi events collected with the BESIII detector at the BEPCII.

Dalitz plot analysis of $\eta\rightarrow\pi^+\pi^-\pi^0$ and $\eta/\eta'\rightarrow\pi^0\pi^0\pi^0$ decays are performed, and the matrix elements measured.

We also present results from amplitude analysis of $\eta'\rightarrow\pi^+\pi^-\pi^0$ and $\eta'\rightarrow\pi^0\pi^0\pi^0$ decays. A significant P-wave contribution from $\eta'\rightarrow\rho^\pm\pi^\mp$ is observed for the first time in the $\eta'\rightarrow\pi^+\pi^-\pi^0$ channel, and the corresponding branching fraction is determined.

The doubly radiative decay $\eta'\rightarrow\gamma\gamma\pi^0$ are studied and the preliminary branching fraction measurements of the inclusive and non-resonant $\eta'$ decays are determined for the first time.