Meson Resonance Production inπ+−dInteractions at 1.23 BeV/c

A report is made of the study of production and decay properties of the ${\eta }^0$, ${\omega }^0$, ${\rho }^0$, and ${\pi }^0$ mesons produced in ${\pi }^{+}-d$ collisions at 1.23 BeV/c in the Berkeley 72-in. bubble chamber. The production processes are analyzed in terms of ${\pi }^{+}$-neutron interactions through the use of an impulse model. A clear enhancement due to the ${N_{\frac{1}{2}}}^{*} \mathrm{}\left(1688\right)\mathrm{}$ resonance is observed in the ${\pi }^0$ (charge exchange) production cross section. The mass of the ${\eta }^0$ meson is found to be ($m_{\eta 0}=552\mathrm{}\pm 3$ MeV), with a branching ratio of $\frac{({\eta }^0\to \mathrm{all}\mathrm{neutrals})}{({\eta }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0)}=3.6\mathrm{}\pm 0.8$, and the partial width $\Gamma \left({N_{\frac{1}{2}}}^{*} \mathrm{}\right(1688)\mathrm{}\to p+{\eta }^0)<\mathrm{}2\mathrm{}$ MeV. The central value of the ${\omega }^0$-meson peak is found to be ($m_{\omega 0}=781\mathrm{}\pm 2$ MeV), with a branching ratio $\frac{({\omega }^0\to \mathrm{all}\mathrm{neutrals})}{({\omega }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0)}=8\mathrm{}\pm 3\%$, and an upper limit of 5% for decay into two charged pions. The production of the ${\omega }^0$ is found to be inconsistent with the single-vector-meson exchange model.