Study of the DecayKL0→π+π−γ

Using a proportional-chamber spectrometer and an array of lead-glass photon detectors, we have observed 1070 ${K_L}^0\to {\pi }^{+}{\pi }^{-}\gamma$ events. We have extracted the branching ratios of the inner-bremsstrahlung component $b{({K_L}^0\to {\pi }^{+}{\pi }^{-}\gamma , k>\mathrm{}20\mathrm{} \mathrm{MeV})}_{\mathrm{IB}}=(1.52\mathrm{}\pm 0.16)\times {10}^{-5\mathrm{}}$, which agrees within errors with the theoretical prediction, and of the directemission component, $b{({K_L}^0\to {\pi }^{+}{\pi }^{-}\gamma )}_{\mathrm{DE}}=(2.89\mathrm{}\pm 0.28)\times {10}^{-5\mathrm{}}$. The $\gamma$-energy spectrum for direct emission shows possible evidence for a deviation from the pure $M1\mathrm{}$ shape.