Ji, XB (reprint author), Chinese Acad Sci, Inst High Energy Phys, Beijing 10049, Peoples R China.
The π N system in J/ψ &RARR; NNπ is limited to be pure isospin 1/2 due to isospin conservation. This is a big advantage in studying N* &RARR; π N from the J/ψ decays, compared with π N and γ N experiments which mix isospin 1/2 and 3/2 for π N system. Based on the 58 million J/ψ data collected at the Beijing Electron Positron Collider, J/ψ &RARR; pπ(-)n and other decay channels are analyzed. In the decay J/ψ &RARR; pπ(-)n, three peaks show up very clearly at 1400 MeV/c(2), 1500 MeV/c(2) and 1670 MeV/c(2) in the π N invariant mass spectrum with additional peak around 2030 MeV/c(2) which may be caused by a new N* resonance.