ππγDecay Mode of NeutralKMesons

Abstract

The decay $K\to {\pi }^{+}+{\pi }^{-}+\gamma$, $\gamma \to e^{+}+e^{-}$ has been observed in the film of the UCRL 72-in. hydrogen bubble chamber exposed to a beam of 1325-MeV/c momentum negative pions. This event unambiguously fits only the decay mode $K\to \pi +\pi +\gamma$, but because the $K\text{'}\mathrm{s}$ life span is almost exactly one ${K_1}^0$ lifetime it is impossible to say whether it is a direct $\pi \pi \gamma$ or inner bremsstrahlung accompanying normal ${K_1}^0\to 2\pi$ decay.