Production and decay of $\eta^{\prime}(958)$ and $\eta (1440)$ in $\bar p p$ annihilation at rest

We report on a study of four reactions in \(\bar{\mathrm p}{\mathrm p}\) annihilation at rest, of \(\bar{\mathrm p}{\mathrm p} \rightarrow 2\pi^ + 2\pi^-\eta\) , \(\bar{\mathrm p}{\mathrm p} \rightarrow 2\pi^ + 2\pi^- 2\pi^0\) , \(\bar{\mathrm p}{\mathrm p} \rightarrow 2\pi^ + 2\pi^-\gamma\) and \(\bar{\mathrm p}{\mathrm p}\rightarrow 4\pi^0\eta\). The \(\eta'\) and the \(\eta\) (1440) are seen in their decays into \(\pi^ + \pi^-\eta\), \(\pi^0\pi^0\eta\) and \(\pi^ + \pi^-\gamma\) ; no signal is seen in the \(4\pi\) invariant mass distribution. Branching ratios for \(\eta'\) and \(\eta\) (1440) production and decay into the different channels are determined. In particular we derive the ratio \(\Gamma_{\eta (1440)\rightarrow\pi^ + \pi^-\gamma}/ \Gamma_{\eta (1440)\rightarrow\pi^ + \pi^-\eta} = 0.111\pm 0.064\).