Asymmetry Parameter for Λ 0 → n π 0

The asymmetry parameter ${\ensuremath{\alpha}}_{0}$ for ${\ensuremath{\Lambda}}^{0}\ensuremath{\rightarrow}n{\ensuremath{\pi}}^{0}$ has been measured relative to ${\ensuremath{\alpha}}_{\ensuremath{-}}$ by comparing the neutron distribution with the proton distribution from the decay ${\ensuremath{\Lambda}}_{0}\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}}$ for polarized ${\ensuremath{\Lambda}}^{0}$ hyperons. A sample of 4760 neutron decay events and 8500 proton decay events gave $\frac{{\ensuremath{\alpha}}_{0}}{{\ensuremath{\alpha}}_{\ensuremath{-}}}=1.000\ifmmode\pm\else\textpm\fi{}0.068$ in good agreement with the $|\ensuremath{\Delta}\stackrel{\ensuremath{\rightarrow}}{\mathrm{I}}|=\frac{1}{2}$ rule.