Study of excited $\Xi$ states in $\psi(3686)\rightarrow{}K^{-}\Lambda\overline{\Xi}^{+}+c.c.$

TL;DR

This study analyzes $ o$K−$ o$Λ$ o$Ξ+ decays in $ ext{ψ}(3686)$ events, identifying and characterizing two excited hyperons, including their quantum numbers, masses, widths, and decay probabilities.

Contribution

It reports the first observation and detailed analysis of $ ext{Ξ}(1690)^-$ and $ ext{Ξ}(1820)^-$ in $ ext{ψ}(3686)$ decays, determining their spin-parities and measuring their properties.

Findings

Observation of $ ext{Ξ}(1690)^-$ and $ ext{Ξ}(1820)^-$ with high significance

Determination of spin-parities: $rac{1}{2}^{-}$ and $rac{3}{2}^{-}$

Measurement of masses, widths, and branching fractions

Abstract

Based on a sample of $(448.1\pm2.9)\times10^{6}$ $\psi(3686)$ events collected with the BESIII detector at BEPCII, the decays of $\psi(3686)\to{}K^{-}\Lambda\overline{\Xi}^{+} + c.c.$ with $\overline{\Xi}^+ \to \overline{\Lambda} \pi^+$, $\overline{\Lambda}\to \overline{p} \pi^+$ are studied.Two excited hyperons, $\Xi(1690)^-$ and $\Xi(1820)^-$, are observed with large significance ($ \gg 10 \sigma$) in the $K^{-}\Lambda$ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of $\Xi(1690)^-$ and $\Xi(1820)^-$ are determined to be $\frac{1}{2}^{-}$ and $\frac{3}{2}^{-}$, respectively. The masses, widths, and product branching fractions of $\Xi(1690)^-$ and $\Xi(1820)^-$ are also measured.