Measurements of the branching fractions for J/psi and psi ' -> Lambda(Lambda)over-bar pi(0) and Lambda(Lambda)over-bar eta

Abstract

We report on a study of the isospin-violating and isospin-conserving decays of the J/psi and psi' charmonium state to Lambda(Lambda) over bar pi(0) and Lambda(Lambda) over bar eta, respectively. The data are based on 225 million J/psi and 106 million psi' events that were collected with the BESIII detector. The most accurate measurement of the branching fraction of the isospin-violating process J/psi -> Lambda(Lambda) over bar pi(0) is obtained, and the isospin-conserving processes J/psi -> Lambda(Lambda) over bar eta and psi' -> Lambda(Lambda) over bar eta are observed for the first time. The branching fractions are measured to be B(J/psi -> Lambda(Lambda) over bar pi(0)) = (3.78 +/- 0.27(stat) +/- 0.30(sys)) x 10(-5), B(J/psi -> Lambda(Lambda) over bar eta) = (15.7 +/- 0.80(stat) +/- 1.54(sys)) x 10(-5) and B(psi' -> Lambda(Lambda) over bar eta) = (2.48 +/- 0.34(stat) +/- 0.19(sys)) x 10(-5). No significant signal events are observed for psi' -> Lambda(Lambda) over bar pi(0) decay resulting in an upper limit of the branching fraction of B(psi' -> Lambda(Lambda) over bar pi(0)) < 0.29 x 10(-5) at the 90% confidence level. The two-body decay of J/psi -> Sigma(1385)(0)<(Lambda)over bar> + c.c. is searched for, and the upper limit is B(J/psi -> Sigma(1385)(0)(Lambda) over bar + c.c.) < 0.82 x 10(-5) at the 90% confidence level.