Study Of ?(3686)??(?)?~0/? At BES?

Baryon spectroscopy provides important opportunity for the study of Hadron microstructure and quantum chromodynamics(QCD)long-range interactions,and has always been an important topic in Hadron physics.With the discovery of J/? particles,charmonium particles such as ?(3686)have also been discovered.The study of charmonium decay is of great significance for understanding the various mechanisms of quantum chromodynamics and charmonium family spectra.At the same time,these studies can check the non-perturbative QCD model and perturbation calculation,so that we can better understand the strong interaction.BES? detector is a high-energy physics experimental device working in the physical energy region of ?-charm,which collects the largest data sample such as ?(3686)in the world.The data with high statistics provide an ideal place for us to study charmonium decay.First of all,this paper uses about 450 million ?(3686)sample collected by BES? to study the ?(3686)????0 process.Through event selection and background analysis,the obvious evidence of the isospin breaking process ?(3686)????0 is observed for the first time,and the statistical significance is more than 3?.The branching fraction is calculated to be B(?(3686)? ???0)=(1.42±0.39±0.16)×10-6,and the upper limit of the branching fraction is determined to be B(?(3686)? ???0)<2.10 × 10-6 at 90%confidence level.The first precice measurement of this process not only complements the important experimental data for the study of charmonium decay,but also provides a unique decay process for the study of flavor symmetry breaking effect of SU(3).In addition,using the same data sample,the partial wave analysis of ?(3686)? ??? is performed for the first time.Through event selection,background analysis and systematic uncertainty estimate,obvious ?(1670)excited states have been observed on the invariant mass distributions of ?? and ??.Using the selected good events,the mass,width and joint decay branching fraction of ?(1670)have been measured to be M(?(1670))=(1672±5±6)MeV/c2,?(?(1670))=(38±10±19)MeV and B(?(3686)? A(1670)?)×B(?(1670)???)=(1.29±0.31±0.63)×10-5,respectively.Based on the results of partial wave analysis,the branching fraction of ?(3686)? ??? is calculated to be B(?(3686)? ???)=(2.34 ±0.18±0.18)×10-5,which is consistent with the PDG result within the error range.