Parity Nonconservation in the Decay of Free and Bound Λ Particles

A quantitative estimate is made of the branching ratio between two-body and more complicated mesonic decay modes for _ΛHe⁴ and _ΛH⁴, as function of their spin J and the ratio p/s of the s- and p-channel amplitudes in free Λ decay. Comparison with the data on _ΛH⁴ decay indicates that $J=1$ is rather improbable and that, with $J=0$, an upper limit on p/s is about unity, a lower limit of 0.45 being obtained from the observations on up-down asymmetry in polarized Λ decay. The theoretical and experimental values for the nonmesonic/mesonic ratio in hypernuclear decay are compared in the light of these limits on p/s. Assuming validity of the ΔT=1/2 rule, the variations in the π^-π⁰ ratio for decays of light hypernuclei ($Z<~2$) due to the effect of the Pauli principle are also estimated. A brief discussion of _ΛH³ decay is given in an appendix.