Precise measurement of the branching fractions of J/ψ → ¯Λπ⁺Σ⁻ + c. c. and J/ψ → ¯Λπ⁻Σ⁺ + c. c.

Based on a data sample of ð10087 44Þ × 106 J=ψ events collected with the BESIII detector, the branching fraction of J=ψ → Λ¯ πþΣ− þ c:c: is measured to be ð1.221 0.002 0.038Þ × 10−3, and the branching fraction of its isospin partner mode J=ψ → Λ¯ π−Σþ þ c:c: is measured to be ð1.244 0.002 0.045Þ × 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.