Measurements of the branching fractions of ψ(3686) → (Σ)over-bar0Λ + c.c: and χcJ(J=0,1,2) → Λ(Λ)over-bar

Based on 4.481 x 10(8) psi(3686) events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay psi(3686)-> (Sigma) over bar0 Lambda+c.c: is measured to be (1.60 +/- 0.31 +/- 0.13 +/- 0.58) x 10(-6), where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays chi cJ ->Lambda(Lambda) over bar are measured via psi(3686)->gamma gamma(cJ), and the branching fractions are determined to be B(chi(c0) -> Lambda(Lambda) over bar) = (3.64 +/- 0.10 +/- 0.10 +/- 0.07) x 10(-4), B(chi(c1) -> Lambda(Lambda) over bar) = (1.31 +/- 0.06 +/- 0.06 +/- 0.03) x 10(-4), B(chi(c2) -> Lambda(Lambda) over bar) = (1.91 +/- 0.08 +/- 0.17 +/- 0.04) x 10(-4), where the third uncertainties are systematic due to the psi(3686) -> gamma chi(cJ) branching fractions.

Automated summary

The branching fraction of the isospin violating decay psi(3686)-> (Sigma) over bar0 Lambda+c.c: has been measured to be significantly smaller than previous measurements based on CLEO-c data sets. The decays chi cJ -> Lambda(Lambda) over bar have also been measured via psi(3686)->gamma gamma(cJ), with calculated branching fractions for different chi_c states.