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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) Aug. 29 – Sep. 4, 2004 Menu 2004 Beijing, China. Outline. Introduction Baryon program at BES N* in the decay of N * and  * in the decay of and others Summary.

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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) Aug. 29 – Sep. 4, 2004 Menu 2004 Beijing, China

  2. Outline • Introduction • Baryon program at BES • N* in the decay of • N* and * in the decay of and others • Summary MENU 04(中国北京)

  3. The Beijing Electron Positron Collider L ~ ~51030 /cm2s at J/ peak Ecm~2-5 GeV MENU 04(中国北京)

  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 MENU 04(中国北京)

  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 MENU 04(中国北京)

  6. J/ decays • relatively large branching ratios (PDG2004) MENU 04(中国北京)

  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. MENU 04(中国北京)

  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 MENU 04(中国北京)

  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% MENU 04(中国北京)

  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+ MENU 04(中国北京)

  11. N* in BES II Preliminary Dalitz Plot: Acceptance and other reasons make the plot asymmetry. MENU 04(中国北京)

  12. N* in Fitting formulark : momentum of anti-neutronq : proton momentum in Mx frame BES II Preliminary MENU 04(中国北京)

  13. N* in Preliminary results: • Possible new N* resonance • L=0 limits it to be 3/2+ or 1/2+ • Detailed information need PWA MENU 04(中国北京)

  14. N* in BES II Preliminary BES II Preliminary MENU 04(中国北京)

  15. from BES II data Events selection • 4 good charged tracks • PID: kaon and at least 1 proton ID • 2 (4C)<20 MENU 04(中国北京)

  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 MENU 04(中国北京)

  17. BES II Preliminary from BES II data PWA is being performed MENU 04(中国北京)

  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 MENU 04(中国北京)

  19. Thank You! MENU 04(中国北京)

  20. “Missing” N* Problem Capstick et al. MENU 04(中国北京)

  21. Mnpi MENU 04(中国北京)

  22. vs pN invariant mass / MC phase space MENU 04(中国北京)

  23. Problems in baryon spectroscopy A. Theoretical problem: What are effective degrees of freedom ? (a) 3q (b) hybrid (c) diquark (d) multi-quark Predicted states: (d) > (b) > (a) > (c) “missing” baryon problem: observed states < (a) predicted states MENU 04(中国北京)

  24. Some results from BES BESI 7.8M J/y Nucl. Phys. A675 (2000) 189c MENU 04(中国北京)

  25. from BESI data two well known N* states found N(1535)S11: M = 1530 10 MeV/c2  = 95 25 MeV/c2 PDG2002: M=15201555MeV/c2  = 100200 MeV/c2 N(1650)S11: M = 1647 20 MeV/c2  = MeV/c2 PDG2002: M=16401680MeV/c2  = 145190 MeV/c2 Phys. Lett. B510(2001) 75 MENU 04(中国北京)

  26. from BESII data Preliminary PWA will be performed MENU 04(中国北京)

  27. Systematic error MENU 04(中国北京)

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