The Study Of ψ(3686)→ Λ(?)ω And J/Ψ→Λ(?)η At BesⅢ

The charmonium decay is an ideal process for studying the baryon spectrum.The highest statistics data samples of J/ψ and ψ(3686)at BESIII,provide us an excellent laboratory to study the excited nucleons and hyperons Λ,Σ,Ω,Δ,and Ξ resonances.Based on the J/ψ and ψ(2S data collected by BESIII,this paper conducts research and analysis on J/ψ ΛΛη and ψ(3686)→ ΛΛω.The process ψ(3686)→ΛΛω is observed for the first time,using(448.1±2.9)× 106ψ(3686)events collected with the BESIII detector.The branching fraction of ψ(3686)→ΛΛω is measured to be(3.30± 0.34(stat.)± 0.29(syst.))× 10-5.In addition,the potential excited A states are investigated by an unbinned maximum likelihood fit to the Dalitz plot.The results hint in agreement with a resonant structure with a mass around 2 GeV/c2,which could be explained as an excited state A*,but its significance(3.0σ)is not sufficient to claim an observation.The corresponding upper limit for the branching fraction Br(ψ(3686)→ΛΛ*+c.c→ΛΛω)is determined to be 1.40 × 10-5 at the 90%confidence level.With the increase of statistics of ψ(3686),a PWA is performed in ψ(3686)→ ΛΛωby using 2712.3 × 106 ψ(3686)events collected with the BESIII detector.Using a sample of 10 billion J/ψ events taken at the BESIII detector,a partial wave analysis(PWA)of J/ψ→ΛΛη is performed for the first time to investigate the possible intermediate states.And the mass,width,and the branching fraction for each component are measured.With the detection efficiency obtained from the MC sample generated with the PWA results,the branching fraction of J/ψ→ΛΛη is also measured,which are determined to be B(J/ψ→ΛΛη)=(20.16±0.12(stat.)±0.78(syst.))× 10-5.Searching for AA threshold enhancement in J/ψ→ΛΛη is performed based on the PWA result,and no clear such enhancement is observed.After considering the systematic uncertainties,the upper limit of B(J/ψ→Xη→ΛΛη)at 90%confidence level is 6.868 × 10-6.