On the Theory of the Meson Decay

1. It was first suggested by Yukawa(1) that the to mesons are un stableand disintegrate spontaneously each into an electron and a neu trino.This assumption was added to his meson theory of nuclear forces in order to account for the beta-decay of the radioactive nuclei, which can then be considered as the virtual emission of a rueson by a nuelear particle and the subsequent decay of the meson. The predietod instability of the meson has received striking con fimationsfrom the cosmic ray observations, As was first pointed out by Euler and Heisenberg(3), the anomalous absorption of the hard component, reported by Ehmert and others was immediatcly explained by this hypothesis. Further, a more direct evidence of the meson decay was obtained byWilliams and Rober(4) who published a cloud chamber photograph of a positivc meson at the end of its range emit tinga positron with energy approximately half the rest energy of the meson. Moreover, Nelson(5) showed, by analysing the experimental data of Neher and Stever(6), that one but not both of the decay products is shower producing. From these expcriments, it is concluded that Yukawa's hypothosis is correct in its outline. However, a serious discrepancy is found wheN a quantitative com