Determination of the number of $\ddot{I}ˆ(3686)$ events taken at BESIII

Abstract

The number of $\ddot{I}ˆ(3686)$ events collected by the BESIII detector during the 2021 run period is determined to be $(2259.3\pm 11.1)\times 10^6$ by counting inclusive $\ddot{I}ˆ(3686)$ hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of $\ddot{I}ˆ(3686)$ events collected during the 2009 and 2012 run periods are updated to be $(107.7\pm 0.6)\times 10^6$ and $(345.4\pm 2.6)\times 10^6$, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of $\ddot{I}ˆ(3686)$ events in the three data samples is $(2712.4\pm 14.3)\times 10^6$.