Properties of Heavy Unstable Particles Produced by 1.3-Bev π- Mesons

A propane bubble chamber has been exposed to a π^- beam of 1.3-Bev kinetic energy. The reactions π^-+p-->Σ^-+K⁺, π^-+p-->Λ⁰+θ⁰, π^-+p-->Σ⁰+θ⁰, can be experimentally distinguished from carbon events. Results based on the first 55 such events are presented. The center-of-mass production distribution of the Σ^- is peaked forward, that of the Λ⁰ backward. No large anisotropies in the angular correlation of production and decay were found, so that we have no evidence for spin in excess of 1/2 for any of the three particles: Σ^-, Λ⁰, or θ⁰. A study of the relative abundance of single and double V production indicates that both Λ⁰ and θ⁰ have either long-lived "states" or neutral decay modes. A statistical analysis gives α¯_Λ⁰=0.3_{- 0.12}^+0.15, α¯_θ⁰=0.3_{- 0.12}^+0.19, for the normal charged decay probabilities (Λ⁰-->π^-+p θ⁰-->π⁺+π^-) of the Λ⁰ and θ⁰, respectively. One event was analyzed to obtain the energy released in Σ^- decay. Σ^--->π^-+n+Q Q=118+/-2.6 Mev. The Σ^- lifetime on the basis of 16 decays is (1.4^+1.6_-0.5)×10^-10 sec.