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Photoproduction of h and h ‘ Mesons on the Nucleon

Photoproduction of h and h ‘ Mesons on the Nucleon. introduction the MAID project t-channel exchanges: poles vs. Regge trajectories D 15 (1675) resonance vs. P 11 (1675) pentaquark summary and conclusion. L. Tiator, Institut für Kernphysik, Universität Mainz. h threshold.

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Photoproduction of h and h ‘ Mesons on the Nucleon

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  1. Photoproduction of h and h‘ Mesons on the Nucleon • introduction • the MAID project • t-channel exchanges: poles vs. Regge trajectories • D15(1675) resonance vs. P11(1675) pentaquark • summary and conclusion L. Tiator, Institut für Kernphysik, Universität Mainz

  2. h threshold K threshold p threshold nonresonant background: large very small large

  3. motivation for g,h and g,h‘ • missing or misidentified resonances • qqq resonances vs. dynamically generated resonances with ppN or with KS, e.g. S11(1535) • exotic resonances: Does the Q+ pentaquark exist? if so, it should have a non-strange partner P11(~1700)

  4. MAID the Mainz-Dubna Unitary Isobar Model K-matrix unitarization unitarization phase determined by the Watson theorem, below 2p threshold relaxed above 2p threshold

  5. ETA-MAID uses a simpler approach without additional unitarization:

  6. Resonances Breit-Wigner form 8 resonances are included in h-MAID : D13(1520)very important for S S11(1535) most important S11(1650) very important D15(1675) very important for S F15(1680) less important D13(1700) unimportant P11(1710) important P13(1720) unimportant

  7. Background Born Terms very small coupling constant:

  8. Vector Meson Exchanges

  9. This description for vector meson exchanges • works fine in the resonance region (W < 2 GeV) • but cannot be extended to high energies

  10. Regge Trajectory Exchanges At high s and low t, it is known that meson photoproduction can be well described by Regge trajectories in the t-channel. Replace pole-like propagator With Regge propagator

  11. Vector Meson Exchanges in  p  h p Fit high-s, low-t data to determine the vector meson couplings gVNNand kVNN Data from DESY (1970)

  12.  Photoproduction Data available in 2001 • Cross sections • MAMI in MainzKrusche et al., Phys. Lett. B358, 40 (1995) MAMI 95 • ELSA in BonnPrice et al., Phys. Rev. C 51, 2283 (1995) ELSA 95 • GRAAL, ESRF in GrenobleRenard et al., Phys. Lett. B528, 215 (2002) GRAAL 02 • Beam asymmetry • GRAAL, ESRF in GrenobleAjaka et al., Phys. Rev. Lett. 81, 1797 (1998) GRAAL 98Kouznetsov (SAID database) GRAAL 01 • Target asymmetry • PHOENICS, ELSA in BonnBock et al., Phys. Rev. Lett. 81, 534 (1998) ELSA 98

  13.  Photoproduction Data after 2001 • Cross sections • GRAAL, ESRF in GrenobleRenard et al., Phys. Lett. B528, 215 (2002) GRAAL 02 • CLAS, Jefferson LabDugger et al., Phys. Rev. Lett. 89, 222002 (2002)CLAS 02 • CB-ELSA in BonnCrede et al., Phys. Rev. Lett. 94, 012004 (2005) BONN 05 preliminary data 2005/06 • Cross sections and Beam Asymmetry • GRAAL (ds/dW and S for proton and neutron)Kouznetsov et al., N*2005 GRAAL 05 • CB-ELSA (s and ds/dW for proton and neutron) Jaegle et al. N*2005 BONN 05

  14. Eta-Maid 2001 compared to data from TAPS@Mainz and GRAAL differential cross section photon beam asymmetry

  15. Comparison with the Eta-Maid 2003 Reggeized Model

  16. with std. vector meson poles and hadronic form factors with reggeized vector mesons both models describe very well the proton data

  17. standard w,r + resonances reggeized w,r only reggeized w,r + resonances

  18. The role of the D15(1675) resonance hN branching ratios in our 2 models: 17 % for the EtaMaid with v.m. poles 0.7 % for the reggeized model

  19. almost a factor 10 !

  20. h-Maid without D15 h-Maid 2001 Comparison with preliminary data from GRAAL diff. c.s. and beam asymm. on neutron (priv. comm. S. Kouznetsov, 2006) bump observed around 1650 MeV

  21. Comparison with preliminary data from CB-ELSA total c.s. on proton and neutron (I. Jaegle, priv. comm. 2006) h - Maid 2001

  22. ETA - MAID 2003 reggeized isobar model (w,r Regge trajectories) isobar model (update of Eta-Maid2001) (preliminary data from CB-ELSA, I. Jaegle, priv. comm. 2006) only the model with the strong D15 can describe the neutron data

  23. problems with the D15(1675) resonance: • in the std EtaMaid model it fits the neutron data very wellbut needs a large branching ratio of bhN= 17 %SU(3)fl for baryon octett gives a prediction of bhN= 2.5 % (Guzey and Polyakov, hep-ph/0512355) • in the Regge model the D15(1675)does not play any important role

  24. effect of a non-strange pentaquark in

  25. quasifree eta photoproduction on the deuteronin collaboration with Alexander Fix ( e.g. A. Fix and H. Arenhövel, Z. Phys. A 359 (1997) 427 ) in impulse approximation:hNN fsi is negligibleNN fsi is larger but only important near thresholdinput: EtaMaid with additional pentaquark state P11(1675)

  26. pentaquark solution

  27. D15 resonance versus Pentaquarkin angular distribution on the neutron both models cannot really describe the differential cross section

  28. Summary on h production • The old EtaMaid 2001 describes new data > 2002 very well • D15 resonance needs a very large hN branching ratio,to describe the photon asymmetry on the protonthis leads to the peak in s(n)/s(p) • a non-strange narrow pentaquark state P11(1675)Fermi averaged in the deuteron would also produce such a peak • angular distributions are not yet conclusive

  29. ’ Photoproduction Data • total cross sections • DESYABBHHM collaboration, PRC 175 (1968) 1669 AHHM collaboration, 1976, Nucl. Phys. B108 (1976) 45 • SAPHIR in BonnR. Ploetzke et al., PL B444, 555 (1998) • differential cross sections • SAPHIR in BonnR. Ploetzke et al., PL B444, 555 (1998) • JLAB/CLASM. Dugger et al., preliminary (2005-2006) • N*2005 Tallahassee and private communication

  30. h photoproduction  p  h p • Born terms are small and can be neglected • t-channel vector meson Regge trajectories arefixed from  p  h p • the sharp rise of the total cross section near threshold is similar to  p  h pandsuggests an S11 resonance (98) (76) (68) threshold

  31.  p  h pTotal Cross Sections total: Regge + S11 Regge trajectories

  32. comparison of old h‘-Maid with SAPHIR(98) data only S11 resonance required P11 or even higher resonances are not really necessary

  33. fit to preliminary JLab/CLAS data (M. Dugger, N*2005 and private comm.)

  34. Summary on h‘ production • The new JLab/CLAS data are very accurate and cover a large kinematical rangeand allow to draw more reliable conclusions • Born terms are negligible, gh‘NN/4p << 0.1 • a reggeization of the t-channel w,ris clearly necessaryin this energy region of E > 1.7 GeV • an S11 resonance at W=1904 MeV (only 8 MeV above threshold)plays the dominant role, similar as in h production • further resonances are needed in order to describe the data:mainly D13(2080) found at W = 2100 MeV, weakly P11 (2100) found at 2083 MeVand P13(1900) found at 1926 MeV 2

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