First observation of the isospin violating decay $J/\psi \to \Lambda {\bar{\Sigma }}^0+c.c.$

M. Ablikim, M. N. Achasov, D. J. Ambrose +353

Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/\psi$ events collected with the BESIII detector, we present results of a study of $J/\psi \to \gamma \Lambda \bar{\Lambda }$ and report the first observ…