Study of excited $\hat{I}ž$ states in $\ddot{I}ˆ(3686)\to K^{-}\hat{I}›\overline{\hat{I}}{ž}^{+}+c.c.$

Abstract

Based on a sample of $(448.1\pm 2.9)\times 10^6$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector at BEPCII, the decays of $\ddot{I}ˆ(3686)\to K^{-}\hat{I}›\overline{\hat{I}}{ž}^{+}+c.c.$ with $\overline{\hat{I}}{ž}^{+}\to \overline{\hat{I}}›\ddot{I}{€}^{+}$, $\overline{\hat{I}}›\to \overline{p}\ddot{I}{€}^{+}$ are studied.Two excited hyperons, $\hat{I}ž(1690{)}^{-}$ and $\hat{I}ž(1820{)}^{-}$, are observed with large significance ($\gg 10\ddot{I}ƒ$) in the $K^{-}\hat{I}›$ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of $\hat{I}ž(1690{)}^{-}$ and $\hat{I}ž(1820{)}^{-}$ are determined to be ${\frac{1}{2}}^{-}$ and ${\frac{3}{2}}^{-}$, respectively. The masses, widths, and product branching fractions of $\hat{I}ž(1690{)}^{-}$ and $\hat{I}ž(1820{)}^{-}$ are also measured.

12 paes, 4 figures