Shin Nan Yang National 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
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
Motivation low energies ─ ChPT high energies, high momentum transfer─ pQCD medium energies ․ LQCD ․ Phenomenology : hadron models, reaction theory QCD Hadronic phenomena 3
Aim: To construct a coupled-channel dynamical model to study N scattering and pion electromagnetic production 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
Meson-exchange N model below 400 MeV 5
Three-dimensional reduction Cooper-Jennings reduction scheme 6
Choose to be given by 7
C.T. Hung, S.N. Yang, and T.-S.H. Lee, Phys. Rev. C64, (2001) 8
Both on- & off-shell Dynamical model for electromagnetic pion production 9
both t B and t R satisfy Fermi-Watson theorem, respectively. 10
DMT Model 11
12
13
14
Frolov et al., PRL,
16
Extension to higher energies coupled , , 2 channels Include resonances R’s with couplings to , , 2 channels coupled , , 2 channels Include resonances R’s with couplings to , , 2 channels 17
18
19
2R 3R 4R T B = V B + V B g 0 T B 20 S11
R 2R 3R No evidence for the 4th S 11 resonance in N -> N No evidence for the 4th S 11 resonance in N -> N 21 Consistent with data from ELSA
Extraction of resonance parameters 22
23
full Need 4 S 11 Resonances 2 =64 2 =3.5 24
(3,3) 25 S13 (3,3), red PDG, blue DMT
(3,3) 26 P11
(2,3) 27 P31
(2,2) 28 D15
(2,2) 29 F15
1st Resonance2nd Resonance3rd Resonance N*WpΓpΓp ΓpΓp ΓpΓp S (1505, 1501) 67 (170, 124) 1642 (1660, 1673) 97 (160, 82) 2065 (2150±70) 223 (350±100) S (1600, 1585) 136 (115, 104) 1775 (1870±40) 36 (1850±50) 2012 (2140±80) 148 (200±80) P (1365, 1346) 179 (210, 176) 1721 (1720, 1770) 185 (230, 378) 1869 (2120±40, 1810) 238 (240±80, 622) P (1700, 1717) 239 (250, 388) 1846 (not listed) 180 (not listed) P (1714) 70 (68) 1896 (1855, 1810) 130 (350, 494) P (1210, 1211) 90 (100, 100) 1509 (1600, 1675) 236 (300, 386) 2149 (1900, 1900±80) 400 (300, 300±100) Pole Positions and Residues in [ MeV ] (preliminary) Red : PDG04 Blue : Arndt95 Green : Cutkovsky80 Orange : Vrana00 30
1st Resonance2nd Resonance3rd Resonance N*WpΓpΓp ΓpΓp ΓpΓp D 13 (3,3) 1516 (1510, 1515) 123 (115, 110) not seen (1680, not seen) not seen (100, not seen) 1834 (1880±100) 210 (160±80) D 33 (2,2) 1609 (1660, 1655) 133 (200, 242) 2070 (1900±100) 267 (200±60) D 15 (2,2) 1657 (1660, 1663) 132 (140, 152) 2188 (2100±60) 238 (360±80) D 35 (2,1) 1992 (1890, 1913) 270 (250, 246) not seen ( 2400±60 ) not seen ( 400±150 ) F 15 (2,2) 1663 (1670, 1670) 115 (120, 120) 1931 (not listed) 62 (not listed) F 35 (2,2) 1771 (1830, 1832) 190 (280, 254) 2218 (2150±100, 1697) 219 (350±100, 112) F 37 (2,1) 1860 (1885, 1880) 201 (240, 236) 2207 (2350±100) 439 (260±100) Pole Positions and Residues in [ MeV ] (preliminary) Red : PDG04 Blue : Arndt95 Green : Cutkovsky80 Orange : Vrana00 31
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
Our analysis at W > 1750 GeV yields considerable strength, which can be explained by a third and a fourth S 11 resonance with masses 1846(47) and 2113(70) MeV 33 The End
(3,4), red PDG, blue DMT 25 S11
(2,2) 35
(3,3) 37
(3,3) 38
(2,2) 40
(2,1 ) 41
(2,2) 43
(2,1) 44