The baryon spectroscopy from [formula omitted] decays

Abstract

J ψ decay at Beijing Electron-Positron Collider (BEPC) is well known as the best place for looking for glueballs. But in fact it is also an excellent place for studying N ∗ and hyperon physics. For J ψ → N Nππ , and N Nππ the πN and ππN systems are limited to be pure isospin 1 2 due to isospin conservation. This is a big advantage in studying N ∗ resonances from J ψ decays, compared with the πN and γN experiments which suffer difficulty on the isospin decomposition of 1 2 and 3 2 . There are also plenty other decay modes of J ψ involving baryon-antibaryon pairs plus mesons which can be used to study N ∗ and hyperon resonances, e.g., looking for the “missing” N ∗ states from J ψ → ppω , ppη′ , pK − Λ , etc.; studying N ∗(1535) → ηp from J ψ → ppη and studying Λ(1405) → Σπ from J ψ → Λ Σ −π + . It provides a new way to study the internal structure of baryon resonances. The newest progress and outlook in this field are presented.