Measurements Of Branching Fraction Of ψ（3686）→Λ(?)η’ At BESⅢ

Experimental studies of charmonium decays take an important role in understanding mechanism and structure of these states.Investigating these decays can also help test and improve non-perturbative QCD theories in the low-energy,as well as deepen our understanding of strong interaction.The Beijing Spectrometer（BESⅢ）is a large particle detector operating at physics energy region ofτcharm,and has collected the largest data sample of J/ψandψ（3686）,which provide an ideal place to study charmonium decays.Base on the approximately 2.7 billion ofψ（3686）events collected with the BESⅢ detector,ψ（3686）→Λ（?）η’is observed for the first time.With the two decay modes ofη’→γπ⁺π^-andη’→ηπ⁺π^-,the statistical significances ofψ（3686）→Λ（?）η’are found to be 6.8σand 10σ.The branching fractions are measured to be（6.62±1.11±0.52）×10^-6 and（8.22±1.12±0.65）×10^-6,where the first uncertainties are statistics and the second are systematic.After combining the two measurements,the branching fraction is determined to be（7.17±0.97）×10^-6,where the uncertainty includes both statistics and systematic.Baryon spectroscopy is an important topic in the study of hadron physics.In this analysis,the invariant mass ofΛη’/（?）η’has been studied.No evident structure ofΛ^*/（?）^* is found base on present statistics.