1. Reaction models of meson production reactions B. Juliá-Díaz Departament d’Estructura i Constituents de la Matèria Universitat de Barcelona (Spain)

2. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 The spectrum Exciting the substructure we learn about the forces which keep the quarks together, e.g. using the quark model picture some of the predicted states are: P11 (939) 0s 0p L=0, S=1/2, J  =1/2 + P33 Δ(1232) L=0, S=3/2, J  =3/2 + S11 (1535) L=1, S=1/2, J  =1/2 - D13 (1520) L=1, S=1/2, J  =3/2 - S31 (1620) L=1, S=1/2, J  =1/2 - D33 (1700) L=1, S=1/2, J  =3/2 - J=1/2 J=3/2 J=1/2 qqq

3. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 The Δ (1232) and others The Delta (1232) resonance stands as a clear peak The region 1.4 GeV – 2 GeV hosts ~ 20 resonances πN  X, πN N*: 1440, 1520, 1535, 1650, 1675, 1680,... Δ : 1600, 1620, 1700, 1750, 1900, … Δ (1232)  100

4. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 The current PDG values π N (L IJ ) N*s Are they all genuine quark/gluon excitations? |N*> =| qqq > Is their origin dynamical?  E.g. some could be understood as arising from meson-baryon dynamics |N*>= | MB > Are they all? 4* ? 3* ? 2* ? Properties are extracted from meson production reactions:  N   N  N   N

5. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Electromagnetic probes Electrons are well suited for baryon resonance studies, several facilities have used them over the last years: Jefferson LAB (USA) GRAAL (Grenoble) MAMI (Mainz) BATES (MIT) ELSA (Bonn) SPring 8 (Japan) Courtesy of D. Leinweber 1. Hard enough: structure needs to be excited. 2. Not too hard: we may find out the constituents but not the way they are glued together. 3. Range of Q 2 : electrons allow to vary the momentum transferred, thus mapping out the structure. e.m.

6. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 desirable properties for reaction models

7. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties 1. Unitarity contraint built in Basic

8. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties: unitarity How do we produce meson-baryon states? Directly Through MB states Through MMB states  We need to incorporate all the possibilities σ TOT (  b) pp S † S=1 Unitarity: Coupled-channels

9. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties 1. Unitarity contraint built in 2. Simultaneous treatment of Electromagnetic Strong interactions Basic

10. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties | Consistency Couplings of mesons to baryons Electromagnetic vertices Coupling of resonances to MB Electromagnetic structure of resonances Consistent description of strong and e.m. e.m.

11. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties 1. Unitarity contraint built in 2. Simultaneous treatment of Electromagnetic Strong interactions 3. Simultaneous description of: Hadroproduction observables (    N,  N, ,  N, …) Electroproduction observables (    N,  N, , ,  N, …) Basic

12. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties | some data p0pp0p p+np+n p+p+ Basic  N  MN

13. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties 1. Unitarity contraint built in 2. Simultaneous treatment of Electromagnetic Strong interactions 3. Simultaneous description of: Hadroproduction observables (    N,  N, ,  N, …) Electroproduction observables (  *    N,  N, , ,  N, …) 4. Chiral symmetry constraints built in 5. Connection with quark gluon mechanisms at high energies Basic

14. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Basic properties | constraints Quark/gluon N* Physics ChPT Basic

15. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 current reaction models (used also with e.m.)

16. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 dynamical coupled channels

17. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical Coupled-Channels Non-resonant + resonant Dressed resonant vertex Resonance self energies Non-resonant amplitude Full integration ? Effective lagrangians, quark models, …? How many channels ? E.m and hadronic simultaneously?

18. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical CC | Juelich ∫vgt Reactions studied: No e.m. yet Juelich Hadronic part: (Effective Lagrangians)    (fit SAID) (~ 1.9 GeV)   η  2006 S. Krewald, J. Haidenbauer, O. Krehl, A. Gasparian, C. Hanhart, Haberzettl Juelich  N, ηN, , ,  8 PWA (J<5/2) | 4 explicit N* (expected progress from Nakayama, Haberzettl, et al.)

19. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical CC|Juelich (II) ∫vgt Physics: Unitarity fulfilled Most relevant channels included (hadronic) Chiral constraints Off-shell effects included  U-channel resonances Strong  coupling responsible for dynamical generation of the P 11 (1440) resonance Technical  Slow evaluation (probably)  Parallel version(?)  Manpower (?)

20. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical CC | SL/EBAC ∫vgt Reactions studied:    (fit DATA )(W<1.65 GeV)  *    (W=1232 MeV)   η  (W< 2 GeV)    (W< 2 GeV)    (W< 2 GeV)    (W< 2 GeV) Sato-Lee /EBAC Hadronic part: (effective lagrangians)    (fit SAID+DATA),    ,  N, ,  J. Durand, B. Julia-Diaz, H. Kamano, T.-S. H. Lee, A. Matsuyama, M. Paris, B. Saghai, T. Sato, N. Suzuki, K.Tsushima 2008 , η , , , , , ,  16 PWA (J<9/2) | 16 explicit N*

21. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical CC | SL/EBAC ∫vgt Physics: Consistent study of most production reactions Most relevant channels included Unitarity fulfilled Off-shell effects included Exact treatment of 3 body cut Chiral constraints Dynamical model solved for complex E K-matrix version also available  U-channel resonances Technical Parallel computing version used extensively  Slow evaluation for  final state observables Talks by Sato, Kamano, Paris

22. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Dynamical CC|Taipei/Mainz ∫vgt Reactions studied: No e.m. yet (expected progress soon) Taipei/Mainz Hadronic part:  N   N (fit SAID)  N  ηN Off-shell effects included Accurate description of hadronic part  Many resonances (33 with 4 new)  Only two channels  Phenomenological  width  Unitarity  Speed plot used to extract N* parameters Chen, Kamalov, Yang, Drechsel, Tiator 2007 , η  16 PWA (J<9/2) | 33 explicit N*

23. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 coupled channels k-matrix

24. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Coupled-channels K-matrix i  [] Key assumption: Examples : Talk by Strakowsky o SAID o Giessen o KVI

25. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 CC K-matrix |SAID i  [] Reactions studied:  *      , η(‘)  SAID (R. A. Arndt, W. J. Briscoe, R. L. Workman, I. Strakovsky) A and B are purely phenomenological polynomials  N,  N, ηN Hadronic part:       η ,  2007 Reference to many other groups

26. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 CC K-matrix |SAID i  [] Physics: N* properties from complex E plane Single energy and energy dependent fits Q 2 evolution of multipole amplitudes Unitarity below  threshold (unphysical) extrapolation (to get pole positions)  K-matrix approximation Technical Fast evaluation Accurate  2 Great one and two meson database handling Updated regularly Open-access (ssh, web) (http://gwdac.phys.gwu.edu)http://gwdac.phys.gwu.edu

27. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 CC K-matrix |Giessen i  [] E.m. Reactions studied:    (fit SAID),  (  )   , , η ,  Giessen (Feuster, Penner, Mosel) Hadronic part:    (fit SAID, KH84)   , η ,  (  )  N,  N,  N, , , ηN,  N V = v bg +v R 2005 S,P,D, F PWs | 11 N*s

28. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Physics: Unitarity fulfilled within the model Hadron and e.m. consistently studied (using effective lagrangians) U-channel resonances included  K-matrix approximation Speed plot to extract N* properties (for “technical reasons”) Technical Fast evaluation CC K-matrix |Giessen (II) i  []

29. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 CC K-matrix |KVI i  [] E.m. Reactions studied:    (fit SAID),  (  )    , , η ,  KVI Scholten, Usov, Timmermans, Shyam,.. Hadronic part:(effective lagrangians)    (fit SAID) (~1.7 GeV)   , η ,  (  )   N,  N  N, , , ηN,  N 2008 S,P,D PWA | 11 explicit N*

30. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 unitary isobar model

31. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Unitary Isobar Model i  [] Reaction model assumption: Reactions studied:  N   N  *N   N MAID  N  η(‘)N (eta(‘)-MAID)  N   N (2pi-MAID)  *N   (kaon-MAID), Examples (up and running): MAID, JLAB/Yerevan Talks by Tiator and Aznauryan  N,  N 2007 Up to F waves, 13 explicit N* D. Drechsel, S.S. Kamalov, L. Tiator, Fix

32. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 UIM|MAID i  [] The phase of the multipole (non-res + res) taken as: Ensures Watson theorem is fulfilled  Assumption above 2  threshold Resonant part: Non resonant part: t  from SAID Full t matrix:

33. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Extract resonance structure (pion electroproduction) Single energy and energy dependent fits Unitary below  threshold  Mixture of PV and PS  coupling  Hadronic information taken from GWU/SAID  Several relevant channels not included, e.g. , ,…  Principal value not included Technical Fast evaluation, Accurate  2 Open-access ( http://www.kph.uni-mainz.de/MAID ) http://www.kph.uni-mainz.de/MAID Being updated regularly No error estimation of N* properties i  [] UIM|MAID(2)

34. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 UIM | CB-Elsa i  [] Reaction model assumption: Reactions studied:  N   N  N  ηN CB-ELSA (Thoma, Anisovic, …)  N    N    N   N  N,  N, ,  2008 S,P,D, F | 21 explicit N*, 5 new

35. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 tree diagram

36. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Tree-diagram Main motivation: Studies of reaction mechanims Key assumption: Reactions assumed to be dominated by a small number of resonances (e.g. specific kinematical regions) T  V = v bg +v R

37. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Tree-diagram (II) Reactions studied: o  N   (Adelseck, Bennhold, Mart, Saghai,…) o  *N   N (Oh, Lee, Titov, Zhao) o  N   N (too many to be listed) o  N   N (Oset, Nacher, Roca, Arenhoevel,…) o  *N   N (Mokeev et al.) o And many more of course Essentially: o Non-resonant usually obtained from Efective Lagrangians, e.g.: o The resonant part :  Effective Lagrangians  Quark models  Parametrizations Talk by Fernández-Ramírez

38. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Physics: Good for exploratory calculations Chiral constraints (in some of them)  Not Unitary  Principal value not included  No off-shell effects Technical Fast evaluation Tree-diagram (III)

39. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Tree-diagram | Example JLAB-MSU V.Mokeev, V.Burkert, (CLAS) Motivation: Extract N* properties from recent CLAS  *    data Extract Q 2 evolution of N* photocouplings JM full  -  ++  +  0 2  direct Procedure: Select direct and isobar production processes 2007   P 33 (1640) F 15 (1685) D 13 (1520) p p   CLAS  CLAS (06)

40. B. Juliá-Díaz, Reaction models for meson production, Oct 13 th 2008 Final wish list Unified easy access/database (ALL DATA for single and double meson) GWU@SAID JLAB ? At least two coexisting competitive full coupled-channels models needed to study model dependence EBAC Juelich ? (Taipei/Mainz) Cross computations between the different approaches E.g. SAID using EBAC non-resonant terms Comparisons of non-observable quantities E.g. Juelich non-resonant vs EBAC non-resonant Build the bridge to microscopic studies END Talks by Ramalho, Giannini, Roberts, Cloet, Richards, Lin, Gross, Zhao, Polyakov, …