Improved Determination of the Neutral Decay Branching Ratios of theK10Meson and theΛ0Hyperon

Abstract

Using a 15-in. bubble chamber filled with methyl iodide, propane, and ethane, we have measured the neutral branching ratios of the ${{K}_{1}}^{0}$ meson and the ${\ensuremath{\Lambda}}^{0}$ hyperon. The neutral modes of the decays were observed directly from the materialized $\ensuremath{\gamma}$ rays. The results are ${B}_{K}\ensuremath{\equiv}\frac{({{K}_{1}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}+{\ensuremath{\pi}}^{0})}{({{K}_{1}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})+({{K}_{1}}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}+{\ensuremath{\pi}}^{0})}=0.288\ifmmode\pm\else\textpm\fi{}0.021$ and ${B}_{\ensuremath{\Lambda}}\ensuremath{\equiv}\frac{({\ensuremath{\Lambda}}^{0}\ensuremath{\rightarrow}n+{\ensuremath{\pi}}^{0})}{({\ensuremath{\Lambda}}^{0}\ensuremath{\rightarrow}p+{\ensuremath{\pi}}^{\ensuremath{-}})+({\ensuremath{\Lambda}}^{0}\ensuremath{\rightarrow}n+{\ensuremath{\pi}}^{0})}=0.291\ifmmode\pm\else\textpm\fi{}0.034.$The ${B}_{K}$ ratio suggests an admixture of $|\ensuremath{\Delta}I|=\frac{3}{2}$ in the ${{K}_{1}}^{0}$ decay consistent with that implied by the decay ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{0}$. The relative phase $\ensuremath{\phi}$ between the $|\ensuremath{\Delta}I|=\frac{1}{2} \mathrm{and} \frac{3}{2}$ amplitudes is determined to be $\ensuremath{\phi}={{0}_{\ensuremath{-}0}}^{+54}$ deg.

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