Cloud-Chamber Study of Negative Strange Particles

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 ${\tau }^{-}$ 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 $K_{\pi 2}$ and $K_{\mu 2}$ decay modes.

3. An analysis of 7 Caltech ${\Xi }^{-}$ 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×${10}^{-10\mathrm{}}$ sec. A rough upper limit to the lifetime of 2×${10}^{-8\mathrm{}}$ sec, based on the predictions of the strangeness theory, is obtained. Angular correlations among the ${\Xi }^{-}$ secondaries are studied, but the statistics are insufficient to permit any significant conclusion. An additional event which is most easily interpreted as a ${\Xi }^{-}$ decay is discussed.

4. The $V^{-}$ events which are neither $K^{-}$ nor ${\Xi }^{-}$ are shown to have a lifetime less than or equal to (${1.52}_{-0.25\mathrm{}}^{+0.38\mathrm{}}$)×${10}^{-10\mathrm{}}$ 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 ${\Sigma }^{-}$ hyperon.

5. It is estimated from a comparison of the numbers of identified ${\Xi }^{-}\text{'}\mathrm{s}$ and $V^{-}\text{'}\mathrm{s}$ that the fraction of ${\Lambda }^0$ particles which decay into charged secondaries is greater than ${0.40}_{-0.11\mathrm{}}^{+0.15\mathrm{}}$, 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.