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Observation of two new N* peaks in J/psi-->ppi-n and ppi+n decays |
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| Authors: | Ablikim M Bai J Z Ban Y Bian J G Cai X Chang J F Chen H F Chen H S Chen H X Chen J C Chen Jin Chen Jun Chen M L Chen Y B Chi S P Chu Y P Cui X Z Dai H L Dai Y S Deng Z Y Dong L Y Du S X Du Z Z Fang J Fang S S Fu C D Fu H Y Gao C S Gao Y N Gong M Y Gong W X Gu S D Guo Y N Guo Y Q Guo Z J Harris F A He K L He M He X Heng Y K Hu H M Hu T Huang G S Huang L Huang X P Ji X B Jia Q Y Jiang C H Jiang X S Jin D P Jin S Jin Y Lai Y F Li F Li G Li H B Li H H Li J Li J C Li Q J Li R B Li R Y Li S M Li W G Li X L Li X Q Li X S Liang Y F Liao H B Liu C X Liu F Liu Fang Liu H M Liu J B Liu J P Liu R G |
| Affiliation: | Institute of High Energy Physics, Beijing 100039, People's Republic of China. |
| Abstract: | The decay J/psi-->NNpi provides an effective isospin 1/2 filter for the piN system due to isospin conservation. Using 58x10(6) J/psi decays collected with the Beijing Electromagnetic Spectrometer at the Beijing Electron Positron Collider, more than 100 thousand J/psi-->ppi-n+c.c. events are obtained. Besides the two well-known N* peaks at around 1500 MeV/c2 and 1670 MeV/c2, there are two new, clear N* peaks in the ppi invariant mass spectrum around 1360 MeV/c2 and 2030 MeV/c2 with statistical significance of 11sigma and 13sigma, respectively. We identify these as the first direct observation of the N*(1440) peak and a long-sought missing N* peak above 2 GeV/c2 in the piN invariant mass spectrum. |
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