New precise measurements of the $\Xi^{0} \to \Lambda \gamma$ and $\Xi^{0} \to \Sigma^{0}\gamma$ decay asymmetries

The decay asymmetries of the weak radiative Hyperon decays $\Xi^{0}\to \Lambda \gamma$ and $\Xi^{0} \to \Sigma^{0}\gamma$ have been measured with high precision using data of the NA48/1 experiment at CERN. From about 52000 $\Xi^{0}\to \Lambda \gamma$ and 15000 $\Xi^{0} \to \Sigma^{0}\gamma$ decays, we obtain for the decay asymmetries $\alpha_{\Xi^{0}\to \Lambda\gamma}$ = -0.704 +- 0.019$_{stat}$ +- 0.064$_{syst}$ and $\alpha_{\Xi^{0}\to \Sigma^{0}\gamma}$ = -0.729 +- 0.030$_{stat}$ +- 0.076$_{syst}$, respectively. These results are in good agreement with previous experiments, but more precise.