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Baryon Spectroscopy at ELSA

Baryon Spectroscopy at ELSA. R. Beck, University Bonn for the CBELSA/TAPS Collaboration SPIN 2010, 27.9-2.10, 2010, Jülich. Motivation. Crystal Barrel experiment. Recent Results:. Summary and Outlook. supported by the DFG within the SFB/TR16. Introduction.

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Baryon Spectroscopy at ELSA

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  1. Baryon Spectroscopy at ELSA R. Beck, University Bonn for the CBELSA/TAPS Collaboration SPIN 2010, 27.9-2.10, 2010, Jülich Motivation Crystal Barrel experiment Recent Results: Summary and Outlook supported by the DFG within the SFB/TR16

  2. Introduction 3.2 GeV photon beam at ELSA used to study meson photoproduction - study the nucleon resonance spectrum Breit Wigner Resonances Total Photon Absorption Cross Section Spectroscopic Notation Isospin Spin

  3. Introduction PDG 2010: Status on nucleon resonances only 7N*and 5D* established in the region 1400 MeV < W < 2000 MeV L. Tiator Energy pattern for the dominant states Various nucleon models predict many more states weak coupling to pN final state Constituent Quark Models insufficient data base Dynamical Models Lattice QCD

  4. Experimental program for N* Common effort at ELSA, JLab and MAMI, Precision data for different final states (pp0, pp0p0, ph, ....) Polarization experiments (beam, target and recoil) “complete experiment” g + p -> p + p- + p+ g +p -> p + p0 + p0 g +p -> p + p0 g +p -> K+ + L g +p -> p + h

  5. Observables in Meson Photoproduction data only for: data needed for: Differential cross section: s Target asymmetry: T Beam asymmetry: S Recoil polarization: P Double polarization: E Double polarization: G Sensitive to: Sensitive to: Crystal Barrel experiment at ELSA: polarized photons, polarized targets and 4p acceptance

  6. (W. Hillert, F. Klein)

  7. Experiments at ELSA • Crystal Barrel Set-Up • BGO-OD Set-Up R. Johnstone, Parallel Session E, Monday 29.9.

  8. Crystal Barrel Set Up at ELSA

  9. Crystal Barrel Set Up at ELSA • Crystal Barrel detector • 1230 CsI crystals • Inner-detector • cylinder of 513 scintillating fibers • forward detector (FWPlug) • 90 CsI crystals with PM’s, 120-300 • forward detector (MiniTAPS) • 216 BaF2 , 10-120 Close to 4p coverage

  10. Polarized Photons Linearly polarized photons: - coherent bremsstrahlung - diamond radiator Circularly polarized photons: - longitudinally polarized electrons - helicity transfer to photon Linearly polarized photons Circularly polarized photons high polarization at low photon energies high polarization at high photon energies (H. Eberhard) (S. Kammer)

  11. Butanol (C4H9OH) Polarized Target „Frozen Spin Target“ First operating horizontal cryostat with integrated solenoid to freeze up the spin Target: Butanol (C4H9OH) Polarization: DNP at high B-field (2.5 T) „freeze“ up the spin (0.4 T) relaxation time T~500h Bonn: H. Dutz, S. Goertz Bochum: W. Meyer, S. Reichertz

  12. Polarized Target Running time over 2500 hours in year 2008 over 2200 hors in year 2009 High. polarization P+ = 83.4 % P- = - 80.9 % fast build-up 05h04min (May/June) 05h39min (August) Pol.-time 06h10min horizontal cryostat in experimental area data taking

  13. Polarization Observables Linearly polarized photons -> beam asymmetry S Circularly polarized photons -> double polarization asymmetry E Longitud. polarized protons Linearly polarized photons -> double polarization asymmetry G Longitud. polarized protons Crystal Barrel experiment at ELSA: New preliminary results for G and E

  14. CBELSA/TAPS Results for ph V. Crede, O. Bartolomy et al., PRL 94 (2005) 012004, EPJ A33 (2007) 133 Meson photoproduction Photon helicity couplings: A1/2 und A3/2 S11(1535) : A1/2 (S11(1535)) only Total cross section: stot ~ |A1/2(S11)|2 + |A1/2(P13)|2 + |A3/2(P13)|2 + ….. D13(1520) : A1/2 (D13(1520)) and A3/2(D13(1520)) P13(1720) : A1/2 (P13(1720)) and A3/2(P13(1720))

  15. Σ η-MAID D15(1675) Eγ=1250 MeV D13(1520) Σ D13(1520) BoGa PWA P13(1720) θηcm Θcm CBELSA/TAPS Results for ph Beam asymmetry: S Higher sensitivity because of interference between different resonance contributions S~ A1/2(S11) * A1/2(P13)+ ….. D. Elsner et al., EPJ A33 (2007) 147 P11(1710)

  16. S11 (1535) P11 (1710) P13 (1720) Helicity dependent cross section for ph reaction: circularly polarized photons longitudinally polarized proton Preliminary results(J. Müller) N1/2 - N3/2 no acceptance correction

  17. S11 (1535) P11 (1710) P13 (1720) Helicity dependent cross section for ph reaction: circularly polarized photons longitudinally polarized proton

  18. Helicity dependent cross section for ph reaction: Preliminary results(J. Müller) Angular distribution N1/2 - N3/2 count rate difference no acceptance correction

  19. S- and G- Asymmetry for ph Eg=1050 MeV reaction: missing mass cut fit to the f-distribution Preliminary results (A. Thiel, M. Grüner) Eg=1050 MeV Eg=1050 MeV __BoGa G S __ SAID __ MAID

  20. S- and G- Asymmetry for ph __BoGa linearly polarized photons reaction: __ SAID longitudinally polarized proton Preliminary results (A. Thiel, M. Grüner) __ MAID S S S Eg=850 MeV Eg=1050 MeV Eg=950 MeV G G G Eg=850 MeV Eg=1050 MeV Eg=950 MeV

  21. P33 (1232) F15 (1680) S11 (1535) Helicity dependent cross section for pp0 reaction: circularly polarized photons longitudinally polarized proton count rate difference acceptance correction Preliminary results(M. Gottschall) N1/2 - N3/2 with acceptance correction + …

  22. Helicity dependent cross section for pp0 reaction: Angular distributions sensitive to interference between resonances Preliminary results(M. Gottschall) N1/2 - N3/2 N1/2 + N3/2 with acceptance correction prediction partial wave analysis __MAID __ SAID __ BoGa

  23. Polarization Observables

  24. S and G-Asymmetry for pp0 Missing Mass reaction: missing mass cut fit to the f-distribution Preliminary results CB(A. Thiel) GRAAL data Eg=1000 MeV Eg=1000 MeV __BoGa __ SAID S G __ MAID

  25. S and G-Asymmetry for pp0 linearly polarized photons reaction: longitudinally polarized proton Eg=966 MeV Eg=1000 MeV Preliminary results (A. Thiel) S S GRAAL data prediction partial wave analysis G G __BoGa __ SAID __ MAID

  26. S and G-Asymmetry for pp0 reaction: Eg=1033 MeV Eg=1066 MeV Preliminary results (A. Thiel) S S GRAAL data prediction partial wave analysis Eg=1033 MeV Eg=1066 MeV G G __BoGa __ SAID __ MAID

  27. S and G-Asymmetry for pp0 reaction: Eg=1100 MeV Eg=1133 MeV Preliminary results (A. Thiel, M. Grüner) S S GRAAL data prediction partial wave analysis G G __BoGa __ SAID __ MAID

  28. Energy dependence Beam-Asymmetry S at q = 110 __without P11 (1440) __ without D13 (1520) __ without F15 (1680) S Double-Polarization-Asymmetry G at q = 110 Eg in MeV G Preliminary results (A. Thiel, M. Grüner) Eg in MeV

  29. World Data Base reaction: Beam asymmetry S Differential cross section First round of double polarization experiments with CB at ELSA: Energy range for G: 600- 1300 MeV Energy range for E: 500- 2100 MeV Asymmetry E Asymmetry G Future plans for CB at ELSA: Extend energy range to 3 GeV * * * * * * * * * * * * * * * * * * * * * Transversally polarized target Installed and first data taken Measurements on the neutron polarized deuteron target

  30. Targetasymmetry in ph

  31. Targetasymmetry in ph

  32. Targetasymmetry in ph

  33. Electromagnetic excitation off the neutron

  34. Electromagnetic excitation off the neutron ELSA data, I. Jaegle, B. Krusche

  35. Experimental evidence from other Labs

  36. New high statistics measurement at MAMI C

  37. Comparison Narrow Structure Effect of photo-excitation of D15(1675) ? Coupled channel effect of S11(1535) and P11(1710) ? Interference effect of S11(1535) and S11(1650) ? New narrow state with stronger photo-coupling to the neutron ? -> polarization observables needed !!

  38. Summary First round of double polarization experiments with CBELSA/TAPS at ELSA Preliminary results for the double polarization observable G and E Model independent partial wave analysis polarization observables are essential different final states are essential Will shed new light on the nucleon excitation spectrum

  39. Complete Experiment 8 well chosen observable have to be measured to determine the production amplitudes (F1,F2,F3 and F4) p- threshold until D+(1232)- region additional constraints: (a) s- and p- wave approximation (b) Fermi- Watson theorem same I, J in the final state same scattering phase dIJ two observable sufficient for “complete experiment” differential cross section : ds/dW beam asymmetry : S above pp- threshold Fermi- Watson theorem not valid any more More observable needed to find unique partial wave solution

  40. Double Polarization Experiment for G reaction: linearly polarized photons longitudinally polarized proton Clear effect from G observed

  41. Helicity dependent cross section reaction: circularly polarized photons longitudinally polarized proton Preliminary results(D. Piontek) N1/2 - N3/2

  42. Crystal Barrel/TAPS Results V. Crede, O. Bartolomy et al., PRL 94 (2005) 012004, EPJ A33 (2007) 133 Meson photoproduction S11(1535) GRAAL S11(1650) D15(2070) CB-ELSA MAMI CLAS PWA Photon helicity couplings: A1/2 und A3/2 Total cross section: stot ~ |A1/2(S11)|2 + |A1/2(D13)|2 + |A3/2(D13)|2 + ….. S11(1535) : A1/2 (S11(1535)) only D13(1520) : A1/2 (D13(1520)) and A3/2(D13(1520))

  43. Bonn-Gatchina-Model Analysis

  44. S-wave coupled channel model

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