Precision Measurement of the Decay $\hat{I}{\pounds }^{+}\to p{\hat{I}}^3$ in the Process $J/\ddot{I}ˆ\to \hat{I}{\pounds }^{+}\bar{\hat{I}}{\pounds }^{-}$

Abstract

Using $(10087\pm 44)\times 10^6$ $J/\ddot{I}ˆ$ events collected with the BESIII detector, the radiative hyperon decay $\hat{I}\pounds \to p{\hat{I}}^3$ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be $\left(0.996\pm 0.021_{stat.}\pm 0.018_{syst.}\right)\times 10^{-3}$, which is lower than its world average value by $4.2$ standard deviations. Its decay asymmetry parameter is determined to be $-0.652\pm 0.056_{stat.}\pm 0.020_{syst.}$. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by $78\%$ and $34\%$, respectively.

9 pages, 4 figures, 1 table