Measurement of ψ(3686) → Λ(Λ)over-barη and ψ(3686) → Λ(Λ)over-barπ0 decays

Ablikim, M.; Achasov, M. N.; Adlarson, P.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I; Ban, Y.; Batozskaya, V; Becker, D.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bloms, J.; Bortone, A.; Boyko, I; Briere, R. A.; Brueggemann, A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.; Chen, H. S.

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摘要

Based on a sample of 448.1 x 10(6) psi(3686) events collected with the BESIII detector, a study of psi(3686) -> Lambda(Lambda) over bar pi(0) and psi(3686) -> Lambda(Lambda) over bar eta is performed. Evidence of the isospin-violating decay psi(3686) -> Lambda(Lambda) over bar pi(0) is found for the first time with a statistical significance of 3.7 sigma, the branching fraction B(psi(3686) -> Lambda(Lambda) over bar pi(0)) is measured to be (1.42 +/- 0.39 +/- 0.59) x 10(-6), and its corresponding upper limit is determined to be 2.47 x 10(-6) at 90% confidence level. A partial wave analysis of psi(3686) -> Lambda(Lambda) over bar eta shows that the peak around Lambda eta invariant mass threshold favors a Lambda* resonance with mass and width in agreement with the Lambda(1670). The branching fraction of the psi(3686) -> Lambda(Lambda) over bar eta is measured to be (2.34 +/- 0.18 +/- 0.52) x 10(-5). The first uncertainties are statistical and the second are systematic.

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