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Shin Nan Yang National Taiwan University

Shin Nan Yang National Taiwan University. Collaborators: S. S. Kamalov ( D ubna) Guan Yeu Chen ( T aipei). 18th International Conference on “Few-body Problems in Physics” August 20 – 26, 2006, Santos, Brazil. 1. Outline. Motivation Previous works

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Shin Nan Yang National Taiwan University

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  1. Shin Nan YangNational Taiwan University Collaborators: S. S. Kamalov (Dubna) Guan Yeu Chen (Taipei) 18th International Conference on “Few-body Problems in Physics” August 20 – 26, 2006, Santos, Brazil 1

  2. Outline • Motivation • Previous works Meson-exchange N model below 400 MeV Dubna-Mainz-Taipei (DMT) dynamical model for pion e.m. production • Extension to higher energies • Conclusion 2

  3. Motivation • low energies ─ChPT • high energies, high momentum transfer─ pQCD • medium energies ․LQCD ․Phenomenology : hadron models, reaction theory QCD Hadronic phenomena 3

  4. Aim: To construct a coupled-channel dynamical model to study N scattering and pion electromagnetic production low energies: e.m. threshold pion production, low energy theorems and compare with ChPT medium energies: N- transition form factors, resonance parameters high energy and high momentum transfer: transition to pQCD region? 4

  5. Meson-exchange  N model below 400 MeV 5

  6. Three-dimensional reduction Cooper-Jennings reduction scheme 6

  7. Choose to be given by 7

  8. C.T. Hung, S.N. Yang, and T.-S.H. Lee, Phys. Rev. C64, 034309 (2001) 8

  9. Dynamical model for electromagnetic pion production Both on- & off-shell 9

  10. both tB and tR satisfy Fermi-Watson theorem, respectively. 10

  11. DMT Model 11

  12. 12

  13. 13

  14. 14

  15. Frolov et al., PRL, 1999 15

  16. 16

  17. Extension to higher energies • coupled , , 2 channels • Include resonances R’s with couplings to , , 2 channels 17

  18. 18

  19. 19

  20. S11 2R 3R 4R - - - - TB = VB + VBg0TB 20

  21. ---------- 1R 2R 3R No evidence for the 4th S11 resonance in N ->  N Consistent with data from ELSA 21

  22. Extraction of resonance parameters 22

  23. 23

  24. 2=64 full Need 4 S11 Resonances 2=3.5 24

  25. (3,3) S13 (3,3), red PDG, blue DMT 25

  26. (3,3) P11 26

  27. (2,3) P31 27

  28. (2,2) D15 28

  29. (2,2) F15 29

  30. Pole Positions and Residues in [ MeV ] (preliminary) Red：PDG04Blue：Arndt95 Green：Cutkovsky80Orange：Vrana00 30

  31. Pole Positions and Residues in [ MeV ] (preliminary) Red：PDG04Blue：Arndt95 Green：Cutkovsky80Orange：Vrana00 31

  32. Summary • The DMT coupled-channel dynamical model gives excellent description of the pion scattering and pion e.m. production data from threshold to first resonance region • The model has been extended up to c.m. energy 2 GeV in the sector and resonance parameters extracted 32

  33. Our analysis at W > 1750 GeV yields considerable strength, which can be explained by a third and a fourth S11 resonance with masses 1846(47) and 2113(70) MeV The End 33

  34. (3,4), red PDG, blue DMT S11 25

  35. (2,2) 35

  36. (3,3) 37

  37. (3,3) 38

  38. (2,2) 40

  39. (2,1) 41

  40. (2,2) 43

  41. (2,1) 44

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