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Reaction models of meson production reactions

Reaction models of meson production reactions. B. Juli á -D í az Departament d’Estructura i Constituents de la Mat è ria Universitat de Barcelona (Spain). The spectrum.

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Reaction models of meson production reactions

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

  2. 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: J=1/2 J=3/2 J=3/2 J=1/2 0p D33 (1700) S31 (1620) L=1, S=1/2, J=3/2- S11 (1535) D13 (1520) L=1, S=1/2, J=1/2- L=1, S=1/2, J=1/2- L=1, S=1/2, J=3/2- 0s P11 (939) P33 Δ(1232) L=0, S=1/2, J=1/2+ L=0, S=3/2, J=3/2+ qqq B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

  4. (LIJ) The current PDG values π N • 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 N*s B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

  5. 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 Hard enough: structure needs to be excited. Not too hard: we may find out the constituents but not the way they are glued together. Range of Q2: electrons allow to vary the momentum transferred, thus mapping out the structure. e.m. B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

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

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

  10. 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. B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

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

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

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

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

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

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

  19. Dynamical CC|Juelich (II) 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 P11(1440) resonance Technical • Slow evaluation (probably) • Parallel version(?) • Manpower (?) ∫vgt B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

  21. Dynamical CC | SL/EBAC 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 ∫vgt B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

  22. Dynamical CC|Taipei/Mainz , η Taipei/Mainz 2007 Chen, Kamalov, Yang, Drechsel, Tiator 16 PWA (J<9/2) | 33 explicit N* 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 Reactions studied: • No e.m. yet (expected progress soon) ∫vgt B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

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

  26. CC K-matrix |SAID Physics: • N* properties from complex E plane • Single energy and energy dependent fits • Q2 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) i[] B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

  28. CC K-matrix |Giessen (II) 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 i[] B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

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

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

  33. UIM|MAID(2) • 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) • Being updated regularly • No error estimation of N* properties i[] B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

  36. 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 = vbg +vR B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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

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

  39. Tree-diagram | Example   P33(1640) F15(1685) D13(1520) p  CLAS  CLAS (06) p+D0 2p direct JM full p-D++ p  JLAB-MSU V.Mokeev, V.Burkert, (CLAS) 2007 Motivation: Extract N* properties from recent CLAS * data Extract Q2 evolution of N* photocouplings Procedure: Select direct and isobar production processes B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

  40. 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 Final wish list Talks by Ramalho, Giannini, Roberts, Cloet, Richards, Lin, Gross, Zhao, Polyakov, … END B. Juliá-Díaz, Reaction models for meson production, Oct 13th 2008

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