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

Abstract.

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 $\Gamma_{\eta (1440)\rightarrow\pi^ + \pi^-\gamma}/ \Gamma_{\eta (1440)\rightarrow\pi^ + \pi^-\eta} = 0.111\pm 0.064$.