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Light Baryon Spectroscopy – Recent Results

Light Baryon Spectroscopy – Recent Results. R. Beck HISKP, University Bonn IWHSS, 16. – 18.April 2012 , Lisbon. Introduction. Recent Results from ELSA, JLab and MAMI:. Narrow structure. Summary and Outlook. supported by the DFG within the SFB/TR16. Introduction.

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Light Baryon Spectroscopy – Recent Results

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  1. Light Baryon Spectroscopy – Recent Results R. Beck HISKP, University Bonn IWHSS, 16. – 18.April 2012 , Lisbon Introduction Recent Results from ELSA, JLab and MAMI: Narrow structure Summary and Outlook supported by the DFG within the SFB/TR16

  2. 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

  3. Introduction talk yesterday by M. Peardon

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

  5. Problem with a unique PWA solution 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 data base” differential cross section : ds/dW beam asymmetry : S above pp- threshold Fermi- Watson theorem not valid any more More observable needed to get a unique partial wave solution

  6. Partial waves for the P33(1232)

  7. Resonance parameter for the P33(1232) O. Hanstein, D. Drechsel, and L. Tiator Phys. Lett. B 385, 45 (1996) R.B. and H.P. Krahn Phys. Rev. Lett. 78, 606 (1997) R.B. and H.P. Krahn Phys. Rev. C61, 035204 (2000)

  8. Problem with a unique PWA solution 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 data base” differential cross section : ds/dW beam asymmetry : S above pp- threshold Fermi- Watson theorem not valid any more More observable needed to get a unique partial wave solution

  9. Problem with a unique PWA solution V. Crede, O. Bartolomy et al., PRL 94 (2005) 012004, EPJ A33 (2007) 133 Meson photoproduction Photon helicity couplings: A1/2 und A3/2 BnGa partial wave analysis: strong P13(1720) contribution S11(1535) : A1/2 (S11(1535)) only D13(1520) : A1/2 (D13(1520)) and A3/2(D13(1520)) Total cross section: stot ~ |A1/2(S11)|2 + |A1/2(P13)|2 + |A3/2(P13)|2 + ….. P13(1720) : A1/2 (P13(1720)) and A3/2(P13(1720))

  10. η-MAID D15(1675) Eγ=1250 MeV D13(1520) Σ D13(1520) BnGa PWA P13(1720) Θcm Problem with a unique PWA solution D. Elsner et al., EPJ A33 (2007) 147 Beam asymmetry: S P11(1710) Higher sensitivity because of interference between different resonance contributions S~ A1/2(S11) * A1/2(P13)+ ….. BnGa partial wave analysis: strong P13(1720) contribution MAID partial wave analysis: D15(1675) and P11(1710) contribution More observable needed to get a unique partial wave solution

  11. 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: ELSA, JLAB, MAMI : polarized photons, polarized targets and 4p acceptance

  12. Today 17.4. 60th birthday of Fritz Klein electron accelerator at the University of Bonn W. Hillert, F. Klein BGO-OD

  13. Experiments at ELSA • Crystal Barrel Set-Up • BGO-OD Set-Up

  14. Crystal Barrel Set Up at ELSA

  15. 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

  16. 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 ELSA, JLAB and MAMI

  17. Butanol (C4H9OH) Polarized Target „Frozen Spin Target“ 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 „transversely polarized Target“ „longitudinally polarized Target“ ELSA, JLAB and MAMI

  18. Polarized Target at ELSA Running time over 2500 hours in year 2008 over 2200 hours in year 2009 over 1500 hours in year 2010 over 1800 hours in year 2011 High. polarization P+ = 83.4 % P- = - 80.9 % fast build-up Pol.-time 06h10min horizontal cryostat in experimental area data taking Bonn: H. Dutz, S. Goertz Bochum: W. Meyer, G. Reicherz

  19. Polarized Target at MAMI Polarized Target running since beginning 2010

  20. Polarized Target at JLAB Polarized Target running since beginning 2007

  21. Beam-Target Polarization Observables

  22. P33 (1232) F15 (1680) S11 (1535) Helicity dependent cross section for pp0 reaction: circularly polarized photons longitudinally polarized proton count rate difference acceptance correction N1/2 - N3/2 with acceptance correction + … Crystal Barrel at ELSA (M. Gottschall, J. Müller)

  23. Helicity dependent cross section for pp0 reaction: Angular distributions sensitive to interference between resonances Crystal Barrel at ELSA (M. Gottschall, J. Müller) N1/2 - N3/2 E~ N1/2 + N3/2 partial wave analysis prediction __BnGa __ SAID __ MAID

  24. S11 (1535) F15 (1680) E-Asymmetry for pp0 (ELSA Results) Crystal Barrel at ELSA (M. Gottschall, J. Müller) SAID: blue line MAID: black line BnGa: red line PWA predictions fail already in 2. resonance region

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

  26. η-MAID D15(1675) Eγ=1250 MeV D13(1520) Σ D13(1520) BnGa PWA P13(1720) Θcm Problem with a unique PWA solution D. Elsner et al., EPJ A33 (2007) 147 Beam asymmetry: S P11(1710) Higher sensitivity because of interference between different resonance contributions S~ A1/2(S11) * A1/2(P13)+ ….. BnGa partial wave analysis: strong P13(1720) contribution MAID partial wave analysis: D15(1675) and P11(1710) contribution More observable needed to get a unique partial wave solution

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

  28. G-Asymmetry for pp0 (ELSA Results)

  29. G-Asymmetry for pp0 (ELSA Results) Crystal Barrel at ELSA (A. Thiel to be published) SAID: red dashed MAID: bluedotted BnGa: black line PWA predictions fail already in 2. resonance region

  30. G-Asymmetry for pp0 (ELSA Results) • Below 1 GeV the discrepancies • can be traced back to the • E0+ and E2- multipoles • s- and d-wave contributions • E0+ multipole • S11(1535), S11(1650) and S31(1620) • E2- multipole • D13(1520) and D33 (1700)

  31. E0+ and E2-Multipoles • E0+ multipole • S11(1535), S11(1650) and S31(1620) • E2- multipole • D13(1520) and D33 (1700) SAID: blue MAID: black BnGa: red line

  32. D13 partial wave • E2- multipole contribution from D13 and D33 partial waves • D13(1520)- resonance in D13 partial wave SAID: blue MAID: black BnGa: red line

  33. S11 partial wave SAID: blue • E0+ multipole contribution from S11- and S31- partial waves • S11(1535)- and S11(1650)- resonances in S11-partial wave MAID: black BnGa: red line

  34. E-Asymmetry for np+ (JLaB Results) Preliminary results CLAS at JLAB(M. Dugger)

  35. E-Asymmetry for np+ (JLaB Results) Preliminary results CLAS at JLAB (M. Dugger)

  36. Polarization Observables with trans. pol. Target Circularly polarized photons -> double polarization asymmetry F Transversely polarized protons Linearly polarized photons -> double polarization asymmetry Hand P Transversely polarized protons -> in addition Beam asymmetry Sand Target asymmetry T

  37. F-Asymmetry for pp0 (MAMI Results) Preliminary results Crystal Ball at MAMI(H.J. Arends, M. Ostrick)

  38. Beam Asymmetry S for pp0 (ELSA Results) Crystal Barrel at ELSA (A, Thiel, J. Hartmann)

  39. Target Asymmetry T for pp0 (ELSA Results) Crystal Barrel at ELSA (J. Hartmann)

  40. Target Asymmetry T for pp0 (ELSA Results) Crystal Barrel at ELSA (J. Hartmann)

  41. Recoil Polarization P for pp0 (ELSA Results) Crystal Barrel at ELSA (J. Hartmann)

  42. Double Polarization Asymmetry H for pp0 Crystal Barrel at ELSA (J. Hartmann)

  43. First Interpretation of Asymmetry

  44. First Interpretation of Asymmetry black line L <= 2 Fit and red line L <= 3 Fit

  45. First Interpretation of Asymmetry L <= 2 Fit truncated partial wave analysis

  46. Target Asymmetry in ph

  47. Target Asymmetry in ph

  48. Target Asymmetry T for ph(ELSA Results)

  49. Target Asymmetry T for ph(ELSA Results)

  50. Electromagnetic excitation off the neutron

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