1. Mainz: Drechsel, Tiator Taipei: Guan Yeu Chen, SNY
P11 resonances with DMT dynamical model for πN scattering and pion e.m. production Shin Nan Yang National Taiwan University
Dubna: Kamalov
Mainz: Drechsel, Tiator
Taipei: Guan Yeu Chen, SNY
The 8th International Workshop on
the Physics of Excited Nucleons,
Jlab, May 17-20, 2011

2. Motivation for DMT model
To construct a meson-exchange model forπN scattering
and e.m. production of pion so that a consistent
extraction of the resonance properties like, mass, width,
and form factors, from both reactions can be achieved.
Comparison with LQCD results requires reliable
extraction.
consistent extractions → minimize model dependence?
The resonances we study are always of the type which
results from dressing of the quark core by meson cloud.
→ understand the underlying structure and dynamics 2

3. Taipei-Argonne πN model: meson-exchange  N model below 400 MeV
Three-dimensional reduction
: Cooper-Jennings reduction scheme which
satisfies soft-pion theorem and unitarity 3

4. Choose to be given by 4

5. Hung, Yang, and Lee, Phys. Rev. C64, 034309 (2001)
renormalization of nucleon mass and pion-nucleon coupling constant done for
P11 channel
Hung, Yang, and Lee, Phys. Rev. C64, (2001) 5

6. DMT πN model: extension of Taipei-Argonne model to energies ≦ 2 GeV
Inclusion of ηN channel in S11
Introduce higher resonances as
indicated by the data
G.Y. Chen et al., Phys. Rev. C 76 (2007) 6

7. Extraction of Breit-Wigner parameters
With only one resonance,
Note that both tB and tR have the same phase of 7

9. We only have elastic πN cut included !!9

10. Self-energy ΣR(E)
Breit-Wigner mass MR and
width ΓR 10

11. Dynamical model for  N →  N
To order e, the t-matrix for  N →  N is written as
two ingredients
vk , tkN
Both on- & off-shell 11

12. Dubna-Mainz-Taipei (DMT)12

13. Test of the backgrounds
Near threshold,

14. Results of DMT model near threshold,14

15. M. Weis et al., Eur. Phys. J. A 38 (2008) 2715

16. Photon Beam Asymmetry near Threshold
Data: A. Schmidt et al., PRL 87 (2001) @ MAMI
DMT: S. Kamalov et al., PLB 522 (2001) 16

17. D. Hornidge
private communication
PRELIMINARY

19. The blue dashed lines correspond to the nonresonant background

20. Bare　　　and physical　　 resonance masses as well as total widths　 , all in units of MeV, single pion branching ratios　　, and background phases　　for　 resonances. Upper lines: our results, lower lines: results of the PDG.
(deg)
**** (PDG)
1612
1418
1445±25
436
325±125 44
65±10 32
*** (PDG)
1798
1803
1710±30
508
180±100
15±5 40
*  (PDG)
2196
2247
2125±75
1020
260±100 42
12±2
2100

21. Pole positions and residues for resonances.
(deg) SP
RM(5)
**** (PDG)
1371
1366
1365±15 95 90
95±15 50 48
46±10
-79
-87
-78
-100±35
RM(6)
*** (PDG)
1746
1721
1756
1720±50
184 92
150
115±75 11 5
10±4
-54
-164
-49
-175±35 RM
* (PDG)
1868
2120±240
238
240±80 7
14±7
-216
35±35

22. Proton helicity element for fits obtained from LE and HE.
MAID 2001
MAID
DMT
PDG 2000
HE fit
-71
-81
-77
-65±4
LE fit
-93

23. black line, full DMT model
Blue dashed line, background only
red dashed line, no 2nd and 3rd P11 resonances in DMT model

24. black line, full DMT model
red dashed line, removing second P11 resonance from DMT model

25. with only P11(1710)
red MAID 2007
black DMT 2001
green SAID (FA06K)

26. red MAID 2007
black DMT 2001
green SAID (FA06K)

27. with addition of a narrow P11 resonance of
mass = 1700 MeV, width = 47 MeV with MAID2007

28. with addition of a narrow P11 resonance of
mass = 1700 MeV, width = 47 MeV with MAID2007

29. SUMMARY
Within DMT model for pion-nucleon scattering and pion photoproduction, parameters for the three P11 resonances have been extracted. The extracted values agree well, in general, with the PDG values.
‧only one pole is found corresponding to the Roper.
‧2nd and 3rd P11 resonances are definitely needed in DMT model.
‧indication for a narrow P11 resonance at around 1700 MeV with
a width ～ 50 MeV both πN and γπ reactions.
The choice of background potentials lead
to excellent agreement with low energy neutral pion production data production data from MAMI.
→ reliable separation of background and resonance
contributions ?