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Observation of a near-threshold enhancement in the pp mass spectrum from radiative J/psi-->gammapp decays |
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| Authors: | Bai J Z Ban Y Bian J G Cai X Chang J F Chen H F Chen H S Chen J Chen Jie Chen J C Chen Y B Chi S P Chu Y P Cui X Z Dai Y M Dai Y S Dong L Y Du S X Du Z Z Dunwoodie W Fang J Fang S S Fu C D Fu H Y Fu L P Gao C S Gao M L Gao Y N Gong M Y Gong W X Gu S D Guo Y N Guo Y Q Guo Z J Han S W Harris F A He J He K L He M He X Heng Y K Hong T Hu H M Hu T Huang G S Huang L Huang X P Izen J M Ji X B Jiang C H Jiang X S Jin D P Jin S Jin Y Jones B D Ke Z J Kong D Lai Y F Li F Li G Li H H Li J Li J C Li K Li Q J Li R B Li R Y Li W Li W G Li X Q Li X S Liu C F Liu C X Liu Fang Liu F Liu H M Liu J B Liu J P |
| Affiliation: | Institute of High Energy Physics, Beijing 100039, People's Republic of China. |
| Abstract: | We observe a narrow enhancement near 2m(p) in the invariant mass spectrum of pp pairs from radiative J/psi-->gammapp decays. No similar structure is seen in J/psi-->pi(0)pp decays. The results are based on an analysis of a 58 x 10(6) event sample of J/psi decays accumulated with the BESII detector at the Beijing electron-positron collider. The enhancement can be fit with either an S- or P-wave Breit-Wigner resonance function. In the case of the S-wave fit, the peak mass is below 2m(p) at M=1859(+3)(-10) (stat)+5-25(syst) MeV/c(2) and the total width is Gamma<30 MeV/c(2) at the 90% confidence level. These mass and width values are not consistent with the properties of any known particle. |
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