Measurements Of Branching Fractions Of ψ（3686）→（?）⁰Λ +c.c.and χ_cJ→Λ（?） At BESⅢ

Experimental measurements of charmonium decays are essential for studying the struc-ture and decay mechanisms of charmonium states.These measurements enable tests of non-perturbative QCD models and perturbative calculations that will lead to a better un-derstanding of the strong interaction.The BESⅢ experiment is a high-brightness particle physics experiment working at tau charm physics energy regions,and has accumulated the largest ψ(3686)samples and so on in the world,the high statistical data provides an ideal place for us to study charmonium decayBased on 4.5 × 108 ψ(3686)events collected with BESⅢ detector at BEPCⅡ.The branching fraction of iso-spin violating decay ψ(3686)→(?)0Λ+c.c.is measured to be B(ψ(3686)→ (?)0A+c.c.)=(1.60±0.31±0.13±0.58)× 10-6,where the first uncertainty is statistical and the second is systematic,the third uncertainty is systematic with continuum interference.This result seems consistent with the theoretical prediction,but an order of magnitude smaller than the measurement result that is(12.3±2.4)× 10-6 based on CLEO-c data setsThe large series of P-wave triplet made by the electromagnetic transition process ofψ(3686)→γχcJ provides a very clean environment to study the exclusive decays of χcJ into baryon and anti-baryon pairs.Hence the branching fraction of χcJ→Λ(?) are measured according to ψ(3686)events collected with BESⅢ detector and the branching fractions are determined to be B(χc0→Λ(?))=(3.64±0.10±0.10±0.07)× 10-4,B(χc1→Λ(?))=(1.31±0.06±0.06±0.03)× 10-4,B(χc2→Λ(?))=(1.91±0.08±0.17±0.04)× 10-4,where the first uncertainty is statistical and the second is systematic,the third uncertainty is systematic due to the uncertainty on the ψ(3686)→γχcJ branching fraction.