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N* Production from J/  decays at BES

N* Production from J/  decays at BES. Ji Xiaobin IHEP, Beijing (Representing BES Collaboration) Sep.26 - 30, 2004 QCD and Light Hadrons (Beijing, China). Outline. Introduction Baryon program at BES N* in the decay of N * and  * in the decay of and others

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N* Production from J/  decays at BES

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  1. N* Production from J/ decays at BES Ji Xiaobin IHEP, Beijing (Representing BES Collaboration) Sep.26 - 30, 2004 QCD and Light Hadrons (Beijing, China)

  2. Outline • Introduction • Baryon program at BES • N* in the decay of • N* and * in the decay of and others • Summary QCD and Light Hadrons

  3. The Beijing Electron Positron Collider L ~ ~51030 /cm2s at J/ peak Ecm~2-5 GeV QCD and Light Hadrons

  4. BESII Detector VC: xy = 100 m TOF: T = 180 ps  counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 %  = 7.9 mr B field: 0.4 T p/p=1.78%(1+p2) z = 3.1 cm QCD and Light Hadrons

  5. Study of Excited Baryon States Motivation • Probe the internal structure of light quark baryons • Search for missing baryonspredicted by quark model • Obtain a better understanding of the strong interaction force in the non-perturbative regime QCD and Light Hadrons

  6. J/ decays • relatively large branching ratios (PDG2004) QCD and Light Hadrons

  7. Pure isospin 1/2 Feynman diagram of the production of For and , N and N systems are limited to be pure isospin 1/2. QCD and Light Hadrons

  8. from BES II data • Events selection • 2 good charged tracks • Q1+Q2 = 0 • |cos| < 0.8 • PID: TOF and dE/dx • Mp > 1.15 GeV • 0.88<Mmiss<1.0 GeV QCD and Light Hadrons

  9. Background Analysis • Estimate the background from the fitting of the data • The Monte Carlo of J/ inclusive decay is also used in the background analysis • Background < 8% QCD and Light Hadrons

  10. N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) N*(1440) ? BES II Preliminary N* in L=0 limits it to be 3/2+ or 1/2+ QCD and Light Hadrons

  11. N* in BES II Preliminary Dalitz Plot: Acceptance and other reasons make the plot asymmetry. QCD and Light Hadrons

  12. N* in Fitting formulark : momentum of anti-neutronq : proton momentum in Mx frame BES II Preliminary QCD and Light Hadrons

  13. N* in Preliminary results: • Possible new N* resonance • L=0 limits it to be 3/2+ or 1/2+ • Detailed information need PWA QCD and Light Hadrons

  14. N* in BES II Preliminary BES II Preliminary QCD and Light Hadrons

  15. from BES II data Events selection • 4 good charged tracks • PID: kaon and at least 1 proton ID • 2 (4C)<20 QCD and Light Hadrons

  16. N*(1535)? N*(1650)? *(1520) *(1690) PS, eff. corrected (Arbitrary normalization) from BES II data BES II Preliminary • Two clear peaks at 1520, 1690 MeV/c2 in pK mass • N* in K mass • PWA is being performed QCD and Light Hadrons

  17. BES II Preliminary from BES II data PWA is being performed QCD and Light Hadrons

  18. Summary • A possible “missing” N* is found • PWA to BESII 58M data is in progress BES II preliminary results: • Clear two peaks around 1520, 1690 in pK mass • N*in K mass • PWA is being performed • Similar structure with • PWA is in progress QCD and Light Hadrons

  19. Thank You! QCD and Light Hadrons

  20. “Missing” N* Problem Capstick et al. QCD and Light Hadrons

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