Paper detail

Measurements of $ψ(3686) \to K^{-} Λ\barΞ^{+} +c.c.$ and $ψ(3686) \to γK^{-} Λ\barΞ^{+} +c.c$

Using a sample of $1.06\times10^8\ \psip$ events produced in $e^+e^-$ collisions at $\sqrt{s}$ = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays $\klx+c.c.$ and $\gklx+c.c.$. We observe two hyperons, $Ξ(1690)^-$ and $Ξ(1820)^-$, in the $K^-Λ$ invariant mass distribution in the decay $\klx+c.c.$ with significances of $4.9 σ$ and $6.2 σ$, respectively. The branching fractions of $\klx+c.c.$, $\ksx+c.c.$, $\psip\toγχ_{cJ}\to γK^- Λ\barΞ^+ +c.c.$ $(J=0,\ 1,\ 2)$, and $\psip\to Ξ(1690/1820)^{-} \barΞ^++c.c$ with subsequent decay $Ξ(1690/1820)^-\to K^-Λ$ are measured for the first time.