Resonances from J / Ψ and Ψ ′ Decays

The Institute of High Energy Physics at Beijing runs an electron-positron collider (BEPC) with a general purpose solenoidal detector, the Beijing Spectrometer (BES)[1], which is designed to study exclusive final states in ee annihilations at the center of mass energy from 3000 to 5600 MeV. In this energy range, the largest cross sections are at the J/Ψ(3097) and Ψ(3686) resonant peaks. At present, the BES has collected about 30 million J/Ψ events and 3.7 million Ψ events. More data are going to be taken. Here I want to show you that their decays provide an excellent place for studying excited nucleons and hyperons – N, Λ, Σ and Ξ resonances.