Cloud-Chamber Study of Negative Strange Particles

Abstract

A detailed analysis of the decays in flight of negative K mesons and hyperons, obtained with the 48-in. cloud chambers in Pasadena, is presented. The principal results are the following: 1. Two new fully measurable τ^− events add to the already strong evidence for the existence of this particle. 2. K^− events with a single charged secondary are shown to be most consistent with the K_(π^2) and K_(μ^2) decay modes. 3. An analysis of 7 Caltech Ξ^− events is shown to lead to a Q value of 65±3 Mev, and a 50% confidence lower limit to the lifetime of 4.6 × 10^(−10) sec. A rough upper limit to the lifetime of 2 × 10^(−8) sec, based on the predictions of the strangeness theory, is obtained. Angular correlations among the Ξ^− secondaries are studied, but the statistics are insufficient to permit any significant conclusion. An additional event which is most easily interpreted as a Ξ^− decay is discussed. 4. The V^− events which are neither K^− nor Ξ^− are shown to have a lifetime less than or equal to (1.52^+(0.38)_(−0.25))×10^(−10) sec and a P^* value, based on their transverse momentum distribution, of 197±7 Mev/c. These values correspond satisfactorily with the presently known properties of the Σ^−hyperon. 5. It is estimated from a comparison of the numbers of identified Ξ−'s and V^−'s that the fraction of Λ^0 particles which decay into charged secondaries is greater than 0.40^(+0.15)_(−0.11), and can, insofar as the present data are concerned, be as high as unity. All errors quoted in the above results are 50% confidence limits.