Investigation of the $\hat{I}”I=1/2$ rule and test of CP violation through the measurement of decay asymmetry parameters in $\hat{I}{ž}^{-}$ decays

Abstract

Using $(10087\pm 44)\times 10^6$ $J/\ddot{I}ˆ$ events collected with the BESIII detector, numerous $\hat{I}{ž}^{-}$ and $\hat{I}›$ decay asymmetry parameters are simultaneously determined from the process $J/\ddot{I}ˆ\to \hat{I}{ž}^{-}\bar{\hat{I}}{ž}^{+}\to \hat{I}›(p\ddot{I}{€}^{-})\ddot{I}{€}^{-}\bar{\hat{I}}›(\bar{n}\ddot{I}{€}^0)\ddot{I}{€}^{+}$ and its charge-conjugate channel. The precisions of $\hat{I}{\pm }_0$ for $\hat{I}›\to n\ddot{I}{€}^0$ and $\bar{\hat{I}}{\pm }_0$ for $\bar{\hat{I}}›\to \bar{n}\ddot{I}{€}^0$ compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of $\hat{I}›\to n\ddot{I}{€}^0$ to that of $\hat{I}›\to p\ddot{I}{€}^{-}$, $⟨\hat{I}{\pm }_0⟩/⟨\hat{I}{\pm }_{\hat{I}›-}⟩$, is determined to be $0.873\pm 0.012_{-0.010}^{+0.011}$, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than $5\ddot{I}ƒ$, which signifies the existence of the $\hat{I}”I=3/2$ transition in $\hat{I}›$ for the first time. Beside, we test for CP violation in $\hat{I}{ž}^{-}\to \hat{I}›\ddot{I}{€}^{-}$ and in $\hat{I}›\to n\ddot{I}{€}^0$ with the best precision to date.

8 pages, 2 figures, 1 table