Measurements of the branching fractions for J/ψ and ψ′→ΛΛ̄π0 and ΛΛ̄η

Abstract

We report on a study of the isospin-violating and isospin-conserving decays of the J/ψ and ψ′ charmonium state to ΛΛ̄π0 and ΛΛ̄η, respectively. The data are based on 225 million J/ψ and 106 million ψ′ events that were collected with the BESIII detector. The most accurate measurement of the branching fraction of the isospin-violating process J/ψ→ΛΛ̄π0 is obtained, and the isospin-conserving processes J/ψ→ΛΛ̄η and ψ ′→ΛΛ̄η are observed for the first time. The branching fractions are measured to be B(J/ ψ→ΛΛ̄π0)=(3.78±0.27stat± 0.30sys)×10-5, B(J/ ψ→ΛΛ̄η)=(15.7±0.80stat± 1.54sys)×10-5 and B(ψ ′→ΛΛ̄η)=(2.48±0.34 stat±0.19sys)×10-5. No significant signal events are observed for ψ ′→ΛΛ̄π0 decay resulting in an upper limit of the branching fraction of B(ψ ′→ΛΛ̄π0)<0.29×10 -5 at the 90% confidence level. The two-body decay of J/ψ→Σ(1385)0Λ̄+c.c. is searched for, and the upper limit is B(J/ψ→Σ(1385)0Λ̄+c.c.)<0.82×10 -5 at the 90% confidence level. © 2013 American Physical Society.