Observation of a Doubly-strange Hyperon $\Xi (1720)$ in $J/\psi \to K^{-}{\Sigma }^0{\bar{\Xi }}^{+}+c.c.$

BESIII Collaboration, M. Ablikim, M. N. Achasov +758

Based on a sample of $(10087\pm 44)\times 10^6$ $J/\psi$ events collected with the BESIII detector at BEPCII, we report the first observation of the decay $J/ψ\rightarrow K^- Σ^0 \b…