Search for $\hat{I}”S=2$ nonleptonic hyperon decays $\hat{I}{\text{c◯}}^{-}\to \hat{I}{\pounds }^0\ddot{I}{€}^{-}$ and $\hat{I}{\text{c◯}}^{-}\to n{K}^{-}$

Abstract

Using $(27.12\pm 0.14)\times 10^8$ $\ddot{I}ˆ(3686)$ events collected by the BESIII detector at the center-of-mass energy of $\sqrt{s}=3.686$ GeV, we search for the first time for two nonleptonic hyperon decays that change strangeness by two units, $\hat{I}{\text{c◯}}^{-}\to \hat{I}{\pounds }^0\ddot{I}{€}^{-}$ and $\hat{I}{\text{c◯}}^{-}\to n{K}^{-}$. No significant signal is observed. The upper limits on their decay branching fractions are determined to be $\mathcal{B}(\hat{I}{\text{c◯}}^{-}\to \hat{I}{\pounds }^0\ddot{I}{€}^{-})<5.4\times 10^{-4}$ and $\mathcal{B}(\hat{I}{\text{c◯}}^{-}\to n{K}^{-})<2.4\times 10^{-4}$ at the $90\%$ confidence level.