Λ0−θ0Production inπ−−PCollisions at 1 Bev

Two examples of ${\Lambda }^0-{\theta }^0$ production have been found in the collision of 1.0-Bev ${\pi }^{-}$ mesons with protons. Data on these two cases are given. The two cases are qualitatively similar, yet there are quantitative differences in terms of the angles of production of the ${\theta }^0$ and ${\Lambda }^0$ particles. One case is internally consistent with the production of a ${\Lambda }^0$ and ${\theta }^0$ directly. The other case, in which the ${\Lambda }^0$ and ${\theta }^0$ particles seem slightly noncoplanar with the incoming ${\pi }^{-}$ meson, is not internally consistent with the direct production of a ${\Lambda }^0$ and ${\theta }^0$. It is likely that either the ${\theta }^0$ or the ${\Lambda }^0$ or both ${\theta }^0$ and ${\Lambda }^0$ are the products of decay of heavier parents. It is also possible that a light particle ($\gamma$ or $\nu$) may be produced simultaneously with the ${\theta }^0$ and ${\Lambda }^0$. If one supposes that the ${\Lambda }^0$ is the product of decay of a heavier parent then the $Q$ of such a parent, were it to decay into a proton and ${\pi }^{-}$ meson, is calculated to be 117±30 Mev. This $Q$ value is close to that of the charged hyperons. A short-lived neutral hyperon of this mass has been predicted by Gell-Mann.