Study of ${A_2}^{-}$ in ${\pi }^{-}p\to {\pi }^{-}p{\eta }^0$ at 5 BeV/c

We report a study of the reaction ${\pi }^{-}p\to {\pi }^{-}p{\eta }^0\to {\pi }^{-}p{\pi }^{+}{\pi }^{-}{\pi }^0$ at 5.0 BeV/c, which gives clear evidence for ${A_2}^{-}\to {\eta }^0{\pi }^{-}$. The observed branching ratio is $R=\frac{({A_2}^{-}\to {\eta }^0{\pi }^{-})}{[{A_2}^{-}\to {\left(\rho \pi \right)}^{-}]}=0.23\mathrm{}\pm 0.08$, and the observed polarization of the $A_2$ is $2{\rho }_{11}\simeq 1$, ${\rho }_{1^{-}1}={\rho }_{{}_{}{}^{-}{}_{}{}^{}11}\simeq 0.5$. We also obtain evidence for ${A_2}^{-}\to X^0{\pi }^{-}$ with an observed branching ratio of $\frac{({A_2}^{-}\to X^0{\pi }^{-})}{[{A_2}^{-}\to {\left(\rho \pi \right)}^{-}]}=0.07\mathrm{}\pm 0.03$.