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Meson Photoproduction with Polarized Targets

Meson Photoproduction with Polarized Targets. L. Tiator, Mainz. p production p 0 at threshold Roper and P 11 (1710) h production S 11 -D 13 phase rotation in threshold region Neutron bump at W = 1680 MeV h ’ production separation of S and P wave multipoles close at threshold

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Meson Photoproduction with Polarized Targets

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  1. Meson Photoproduction with Polarized Targets L. Tiator, Mainz • p production • p0 at threshold • Roper and P11(1710) • h production • S11-D13 phase rotation in threshold region • Neutron bump at W = 1680 MeV • h’production • separation of S and P wave multipoles close at threshold • h’ on the deuteron

  2. Introduction if the amplitudes (multipoles) are real or if the Watson theorem can be applied we only needs to measure a real number for each partial wave if we can neglect all D- and higher partial waves we only have to deal with 4 real quantities: E0+, E1+, M1+, M1-or E0, P1, P2, P3 and we are done with ds/dW and S without worrying about target or recoil polarization 2 very famous examples, both from MAMI: p0 p partial waves at threshold p0 p, p+ n with full isospin separation in the D region

  3. But for all other cases, where the imaginary parts are unknown we need nucleon polarizations, either polarized targets or recoil polarization measurements

  4. Pion photoproduction • at threshold the photon asymmetry S at from threshold to 200 MeV is very important from all calculations and partial wave analyses up to now, only ChPT is able to describe it (by fitting LECs) most other calculations get even an opposite sign near threshold • P11(1440) and P11(1710) the P11 resonances are partially hidden states they are very difficult to isolate and are most debated among all resonances

  5. the photon asymmetry S at from threshold to 200 MeV is very important for all calculations and partial wave analyses up to now, only ChPT is able to describe it (by fitting LECs) also dispersion relations can not describe the asymmetry

  6. P11 resonances the M1- multipole is only poorly known because most observables are very insensitive on this multipole but it is very important because of our interest in the Roper resonance with MAMI B we had already started to measure the G observable, which gives the most direct access to M1- (pending proposal) now in the same channel we can further look into the second P11, which could be a verry narrow state and is currently debated

  7. Eta photoproduction • S11(1535) plays an outstanding role in g,h and e,e‘h and and dominates the total cross section completely • at higher energies: S11(1650), P11(1710), P13(1720) play some role • around Eg=1 GeV or W=1670 MeV a surprising structure appears in g,h on the neutron (quasi-free) which is still not fully explained speculations about narrow P11(1680) (pentaquark) or strong D15(1675) (EtaMaid) or P11(1710) in coupled-channels approach (Gießen model) • small resonance contributions can be observed with polarization observables as interferences with the large S wave, • e.g. D13(1520) is clearly visible in S(q), • even with a branching of only GhN/ Gtotal = 0.0006

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  9. Eta photoproduction • S11(1535) plays an outstanding role in g,h and e,e‘h and and dominates the total cross section completely • at higher energies: S11(1650), P11(1710), P13(1720) play some role • around Eg=1 GeV or W=1670 MeV a surprising structure appears in g,h on the neutron (quasi-free) which is still not fully explained speculations about narrow P11(1680) (pentaquark) or strong D15(1675) (EtaMaid) or P11(1710) in coupled-channels approach (Gießen model) • small resonance contributions can be observed with polarization observables as interferences with the large S wave, • e.g. D13(1520) is clearly visible in S(q), • even with a branching of only GhN/ Gtotal = 0.0006

  10. Eta photoproduction • S11(1535) plays an outstanding role in g,h and e,e‘h and and dominates the total cross section completely • at higher energies: S11(1650), P11(1710), P13(1720) play some role • around Eg=1 GeV or W=1670 MeV a surprising structure appears in g,h on the neutron (quasi-free) which is still not fully explained speculations about narrow P11(1680) (pentaquark) or strong D15(1675) (EtaMaid) or P11(1710) in coupled-channels approach (Gießen model) • small resonance contributions can be observed with polarization observables as interferences with the large S wave, • e.g. D13(1520) is clearly visible in S(q), • even with a branching of only GhN/ Gtotal = 0.0006

  11. Eta photoproduction • S11(1535) plays an outstanding role in g,h and e,e‘h and and dominates the total cross section completely • at higher energies: S11(1650), P11(1710), P13(1720) play some role • around Eg=1 GeV or W=1670 MeV a surprising structure appears in g,h on the neutron (quasi-free) which is still not fully explained speculations about narrow P11(1680) (pentaquark) or strong D15(1675) (EtaMaid) or P11(1710) in coupled-channels approach (Gießen model) • small resonance contributions can be observed with polarization observables as interferences with the large S wave, • e.g. D13(1520) is clearly visible in S(q), • even with a branching of only GhN/ Gtotal = 0.0006

  12. eta photoproduction near threshold

  13. mainmultipoles in thethresholdregion Wthreshold = 1487 MeV < Wcm < 1600 MeV Ethresh=709 MeV < Elab < 900 MeV E0+ S11(1535) dominated E2- , M2- D13(1520) dominated E1+ , M1+ background (Born, w, r) here we will use the helicity multipoles A,B: A0+ = E0+ A2- = (3 M2- - E2- ) / 2 B2- = E2- + M2- B1+ = E1+ - M1+

  14. fit to the data

  15. no additional information in these „exotic“ observables

  16. only T, G and Ox‘ are sensitive to the phase rotation T around 30°-60° and 120°-150° G between 45°- 135° Ox‘ between 30°- 150°

  17. Beam-Recoil Double Polarization Experiment in 2007 at MAMI-A1p( e, e´p )hin search for the phase rotation in eta electroproduction

  18. Recoil Polarization in plane: f = 0orp single polarization: double polarization:

  19. confirms the phase rotation

  20. The question remains: Is the phase rotationof hadronic or electromagnetic origin? This can be answered in quasi-free h production on the deuteron

  21. the neutron bump in eta photoproduction at W=1670-1680 MeV

  22. schematic view of g,h on the neutron

  23. Photoproduction of h mesons on the deuteron in the presence of a narrow P11(1670) resonance ( A. Fix, L.T., M.V. Polyakov, EPJ A in print ) model with a strong D15 : model with a narrow P11 : resonance parameters for the pentaquark in our calculations:

  24. GRAAL measurements of the beam asymmetry on the proton and on the neutron

  25. Photon Beam Asymmetry on the Proton data: Bartalini et al., GRAAL 2007 EtaMaid CQM, Saghai, Li Bonn pw analysis, Sarantsev et al.

  26. comparison of GRAAL proton data with pentaquark solutions data: Bartalini et al. GRAAL 2007 EtaMaid Bonn pw analysis Sarantsev et al. ReggeMaid + P11(1670) ReggeMaid - P11(1670) the proton data does not show any pentaquark signature !!

  27. can we do something to solve this puzzle? also here the target polarization can very well distiguish between different models, see SFB-MAMI proposal 2007

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