Precise measurement of the branching fractions of J/ψ → Λ ¯ π+ ς-+ c. c. and J/ψ → Λ ¯ π- ς++ c. c.

Based on a data sample of (10087±44)×106 J/ψ events collected with the BESIII detector, the branching fraction of J/ψ→Λ¯π+ς-+c.c. is measured to be (1.221±0.002±0.038)×10-3, and the branching fraction of its isospin partner mode J/ψ→Λ¯π-ς++c.c. is measured to be (1.244±0.002±0.045)×10-3 with improved precision. Here the first uncertainties are statistical and the second ones systematic. The isospin symmetry of the ς baryon in charmonium hadronic decay and the "12% rule"are tested, and no violation is found. The potential of using these channels as ς baryon sources for nuclear physics research is studied, and the momentum and angular distributions of these sources are provided.