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The status of the Excited Baryon Analysis Center

The status of the Excited Baryon Analysis Center. B. Juli á -D í az Departament d’Estructura i Constituents de la Mat è ria Universitat de Barcelona (Spain). Summary. Motivation Model used at EBAC@JLAB , , , production: Hadronic production   Photoproduction  

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The status of the Excited Baryon Analysis Center

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  1. The status of the Excited Baryon Analysis Center B. Juliá-Díaz Departament d’Estructura i Constituents de la Matèria Universitat de Barcelona (Spain)

  2. Summary • Motivation • Model used at EBAC@JLAB • , ,, production: Hadronic production  Photoproduction   Electroproduction *  • Expected during 2010

  3. Baryon Resonances Exciting the substructure we can 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

  4. 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

  5. E.m. probes Originaly, the hope was that probing the structure with electrons would minimize the “hadronic” debris and would give a cleaner access to the properties of nucleons and resonances • Jefferson LAB (USA) • GRAAL (Grenoble) • MAMI (Mainz) • BATES (MIT) • ELSA (Bonn) • SPring 8 (Japan) (Courtesy of D. Leinweber)

  6. Electroproduction of mesons M g* N N N N* Main elements: Strong-strong interactions Hadronic structure of Resonances Electromagnetic structure of Resonances Coupled-channels

  7. EBAC plan and method

  8. Dynamical Coupled-Channels Analysis @ EBAC EBAC@JLAB Reaction Data N* properties N-N* form factors Hadron Models Lattice QCD QCD

  9. Non-resonant + resonant Dressed resonant vertex Resonance self energies Non-resonant amplitude (resummation) Formalism (DCC)

  10. EBAC-DCC • Partial wave amplitude of a b reaction: • Reaction channels: • Potential: 2-body v potential (no ppN cut) 2-body Z potential (with ppN cut) bare N* state A. Matsuyama, T. Sato, T.-S.H. Lee, Phys. Rep. 2007

  11. Two body v’s (strong) 5 diagrams s-ch N u-ch N u-ch D t-ch r t-ch s 3 diagrams s-ch N u-ch N t-ch p 2 diagrams s-ch N u-ch N 2 diagrams s-ch N t-ch r 2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 1 diagram s-ch N 1 diagram s-ch N 2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N 4 diagrams s-ch N u-ch N t-ch p t-ch w 2 diagrams s-ch N u-ch N 2 diagrams s-ch N u-ch N Total 36 diagrams 4 diagrams s-ch N u-ch N u-ch D t-ch r 2 diagrams s-ch N u-ch N

  12. Two body v’s (e.m.) 2 diagrams s-ch N u-ch N 4 diagrams s-ch N u-ch N t-ch r contact 5 diagrams s-ch N u-ch N u-ch D t-ch p contact 2 diagrams s-ch N u-ch N 7 diagrams s-ch N u-ch N u-ch D t-ch p t-ch r t-ch s contact Total 20 diagrams

  13. EBAC framework overview Physics: • Non-resonant obtained from phenomenological Lagrangians • Unitarity fulfilled within the model • Most relevant channels included • Up to now , ,  (, , ), near future  • Consistent study of all production reactions • Correct treatment of 3 body cut Technical • Parallel computing version of the codes needed

  14. Hadronic part(essential starting point)

  15. MBMB (up to 2 GeV) We introduce explicitly (impose) a minimal number of bare poles, 16 of 23 (4* and 3* from PDG): N: S11(2), P11(2), P13(1), D13(2), D15(1), F15(1) Δ: S31(1), P31(1), P33(2), D33(1), F35(1), F37(1)

  16. Technical aspects • Involved system of coupled integral equations with singularities. Supercomputing Resources NERSC LBNL (>500 kh, 07/10) PI: TSH Lee BSC, Spain (340 kh, 07/08), PI: B. Julia-Diaz Need for extensive parameter search. Several unknowns: e.g. couplings of resonances to MB states

  17. : comparisons to data EBAC SAID06

  18. : comparisons to data (ii) d/d Polarization Data obtained through R. Arndt et al, SAID , gwdac.phys.gwu.edu B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

  19. : comparing amplitudes • Amplitudes compared to GWU/SAID amplitudes for the I=1/2 sector Imaginary part of the Amplitudes Real part of the Amplitudes B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

  20. : comparing TCS • Total Cross sections compared to experimental data • Prediction for the total cross sections for each individual channel B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rev. C 76, 065201 (2007)

  21. : vs other approaches From M. Paris talk at INT 2009 and R. Arndt talk at Badhonnef 2009

  22.    TCS s Previous works, mostly tree level: • Meissner et al (1995) • Oset et al (1985) Not used to constrain the model. H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) 025206

  23.   , distributions Invariant mass distributions Full model Phase space Data handled with the help of R. Arndt H. Kamano, B. Julia-Diaz, TSH Lee, A. Matsuyama, T. Sato, Phys. Rev. C 79 (2009) 025206

  24. Properties of N*(strong)

  25. Resonance states Analytic continuation of T(W) to the unphysical sheet by using contour deformation Poles can be both in the non-resonant and resonant amplitudes One can search for poles of T as a function of W (p’s are arbitrary) Resonance Mass Extraction of Resonances from Meson-Nucleon Reactions. N. Suzuki, T. Sato, T.-S.H. Lee, Phys. Rev. C 79 (2009) 025205; arXiv:0910.1742, part of Suzuki’s PhD Thesis

  26. Dynamical origin of N(1440) Within our framework the three P11 states evolve from the same bare state. In the fig: evolution of the pole position as we increase the self energy N. Suzuki, B. Julia-Diaz, H. Kamano, A. Matsuyama, TSH Lee, T Sato, arXiv: 0909.1356

  27. EBAC current N*

  28. Electromagnetic part

  29. E.m. meson production Goal: Make use of the vast database for single and double pion photo and electroproduction reactions (JLAB, ELSA, MAMI, …) to: • Look for yet unseen resonances • Confirm the existence of the N*s seen in the hadronic reactions • Extract resonance properties: • Couplings to meson-baryon • Electromagnetic structure

  30. Schematic view Consequence of Unitarity g* N N N*

  31. Single pionphotoproduction Consider up to W = 1.6 GeV. Data considered: • Differential cross sections •  p 0 p (8793) •  p + n (5063) • Photon asymmetry (Sigma) •  p 0 p(1204) •  p + n (881) Analysis performed at specific energies. B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, L.C. Smith, Phys. Rev. C77, 045205 (2008)

  32. Single pionphotoproduction Comparison to data • Total cross section • Differential cross sections • Target polarization p+n p0p σTOT (b) B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, L.C. Smith, Phys. Rev. C77, 045205 (2008)

  33. Electroproduction • Consider W<1.65 MeV and Q2<1.45 GeV2 • No assumption on the Q2 dependence of the helicityamplitudes • Resonances which play a role: S11, P11, P33, D13 • Could not fit all the structure functions simultaneously • Performed several fits to clarify the situation Fit1:T+ L , LT , TT , p(e,e’0)p[Joo et al. PRL02] Fit2 all p(e,e’+)n, p(e,e’0)p Fit3 p(e,e’0)p[Joo et al. PRL (2002 & 2003)] Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, 025207 (2009).

  34. Data at Q2<1.45 GeV2 Fit1 Fit3 Fit2

  35. Structure functions (ii) Q2 = 0.4 GeV2 p+n Solid: Fit1 Dashed:Fit2 Dotted: Fit3 Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, Phys. Rev. C 80, 025207 (2009).

  36. Coupled channels effects Q2 = 0.4 GeV2 Solid Full Fit1 Dashed only N intermediate (in e.m. piece) Data from http://clasweb.jlab.org/physicsdb/

  37.  Study of two pionphotoproduction: • Good description near threshold • Reasonable shape of angular distributions • Not good description of the total cross sections of p00and p+-above 1440 MeV- Previous (tree level) works include • Meissner (1994) • Gomez Tejedor, Roca,(1993) • Fix et al (2005) H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv:0909.1129(2009) (Phys. Rev. C in press)

  38. In progress (~ 2010) EBAC second generation model: Full Combined (global fit) analysis of: • N N, N (W<2 GeV) • N    N (W<2 GeV) • N  N (W<2 GeV) • N    N (W<2 GeV) • N  N (W<2 GeV) N* structure extraction • *N  N (W<2 GeV, Q2<4 GeV2) • *N    N (W<2 GeV) • *N  N (W<2 GeV) WEBPAGE: http://ebac-theory.jlab.org

  39. BACKUP

  40. EBAC@JLAB MANPOWER: Leader (ANL/JLAB): • T.-S.H.Lee Postdocts (JLAB): • H. Kamano • S. Nakamura • K. Tsushima • A. Sibirtsev Starting date: • 2006 EXTERNAL COLLABORATORS: • T. Sato, N. Suzuki (Osaka) • A. Matsuyama (Shizuoka) • B. Julia-Diaz (Barcelona) • B. Saghai, J. Durand (Saclay) WEBPAGE: http://ebac-theory.jlab.org

  41. Timeline of EBAC results • Full DCC Formalism A. Matsuyama, T.-S.H. Lee, T. Sato, Phys. Rep. (2007) • Hadronic piece fixed (NN, N)(W<2 GeV) B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2007) J. Durand, B. Julia-Diaz, T.-S.H. Lee, T. Sato, B. Saghai, PRC (2008) • NN (W<1.6 GeV) B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, LC Smith, PRC (2008) • NN H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, PRC (2008) • Analytic continuation N. Suzuki, T. Sato, T.-S.H. Lee, PRC (2008) • *N (W<1.6 GeV, Q2<1.5 GeV2) B. Julia-Diaz, H. Kamano, T.-S.H. Lee, A. Matsuyama, T.Sato, , PRC (2009) • N (W<1.8 GeV) H. Kamano, B. Julia-Diaz, T.-S.H. Lee, A. Matsuyama, T. Sato, PRC (2010)

  42. Multi step (unitarity) How do we produce meson-baryon states? • Directly • Through MB states • Through MMB states  • We need to incorporate all the possibilities • Unitarity Coupled-channels p σTOT (b)

  43. Structure functions Q2 = 1.45 GeV2 p0p Solid: Fit1

  44. , N* effects H. Kamano, B. Julia-Diaz, A. Matsuyama, T.-S.H. Lee, T. Sato, arXiv:0909.1129(2009), Phys. Rev. C in press

  45. PDG *s and N*’s origin • 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 > • Most of their properties are extracted from • N  N • N  N

  46. Z terms Z

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