Production of Heavy Unstable Particles by Negative Pions

In addition to two previously discussed cloud-chamber examples of $V$-particle production by 1.5-Bev ${\pi }^{-}$ mesons from the Cosmotron, four further examples are discussed here. In two of the new examples a ${\Lambda }^0\left({V_1}^0\right)$ and a ${\vartheta }^0\left({V_4}^0\right)$ are seen to decay in a geometry indicating that they were produced together in a ${\pi }^{-}-p$ collision. A third example is best interpreted as production of a ${\Lambda }^{-}\left({V_1}^{-}\right)$ together with a $K^{+}\left({V_2}^{+}\right)$ by a ${\pi }^{-}$ colliding with a proton. A fourth example show a probable ${\Lambda }^{-}$ decaying into a ${\pi }^{-}$ and a neutron with a $Q$ value of about 130 Mev. A cross section of ∼1 millibarn for $V$-particle production is inferred from the number of ${\pi }^{-}-p$ collisions observed.