First measurement of the absolute branching fractions of $\hat{I}{\pounds }^{+}$ nonleptonic decays and test of the $\hat{I}”I=1/2$ rule

Abstract

Based on $(10087\pm 44)\times 10^6$ $J/\ddot{I}ˆ$ events collected by the BESIII detector at the center-of-mass energy $\sqrt{s}=3.097$ GeV, the first absolute measurement of the branching fractions for the decays $\hat{I}{\pounds }^{+}\to p\ddot{I}{€}^0$ and $\hat{I}{\pounds }^{+}\to n\ddot{I}{€}^{+}$ is performed. The branching fractions are determined to be $B_{\hat{I}{\pounds }^{+}\to p\ddot{I}{€}^0}=(49.79\pm 0.06\pm 0.22)\%$ and $B_{\hat{I}{\pounds }^{+}\to n\ddot{I}{€}^{+}}=(49.87\pm 0.05\pm 0.29)\%$, where the first uncertainties are statistical and the second systematic. These results show significant deviations from the PDG values for both decays, with differences of 4.4$\ddot{I}ƒ$ for $\hat{I}{\pounds }^{+}\to p\ddot{I}{€}^0$ and 3.4$\ddot{I}ƒ$ for $\hat{I}{\pounds }^{+}\to n\ddot{I}{€}^{+}$. Furthermore, the $\hat{I}”I=1/2$ rule is tested in nonleptonic $\hat{I}{\pounds }^{\pm }$ decays. The observed results deviate from zero by more than $5\ddot{I}ƒ$, indicating the presence of the $\hat{I}”I=3/2$ transition amplitude in the $\hat{I}\pounds$ hyperon decays.