CXV. Evidence for the β-decay of a K-meson

Abstract

The decay at rest of a K-meson in which the secondary particle appears to be an electron of ~90mev has recently been observed. The secondary particle, after traversing a distance of 2.3 cm in the emulsion, appears to have been sharply deviated; thereafter, the track is closely similar to that of a slow electron. The grain density in the track, before and after the deviation, is indistinguishable from the ‘plateau value’. The most plausible explanation of this behaviour is that it is due to the sudden loss of energy of an electron through the production of bremsstrahlung. Alternatively, the secondary particle could be assumed to be (a) a π-meson which interacts with a nucleus and undergoes change exchange, the product nucleus subsequently suffering β-decay, or (b) a μ-meson which decays in flight. The last two possibilities have been considered and appear very improbable.