Photoproduction of η-mesons on protons in the resonance region: The background problem and the third S11-resonance

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Abstract

We have constructed an isobar model for the η-photoproduction on the proton in the energy region up to the photon lab energy K0 = 3 GeV. The database involved into the fitting procedure includes precise results for the cross-section and for the T-asymmetry of the process γp → ηp near threshold obtained at MAMI and ELSA as well as recent results for the Σ-asymmetry and for the angular distribution measured at higher energies in Grenoble and also more recent measurements performed at JLab for the photon energies up to 2 GeV. The model includes twelve nucleon resonances: S 11(1535), S11(1650), S11(1825), P 11(1440), P13(1720), D13(1520), D 15(1675), F15(1680), F17(1990), G 17(2190), G19(2250), H19(2220), and the background consisting of the nucleon pole term and the vector meson exchange in the t-channel. To explain the observed energy dependence of the integrated cross-section, two s-wave resonances, S11 (1650) and S 11(1825), have to be taken into account along with the dominating S11(1535). The integrated cross-section as well as the angular distribution and Σ-asymmetry predicted by the model are in good agreement with the data. Above the photon energy K0 = 2 GeV, the calculated cross-section exhibits an appreciable dependence on the ρ- and ω-meson contribution, whose coupling with nucleons is not well defined. Several versions of extending the model to higher energies are considered.

Original languageEnglish
Pages (from-to)97-104
Number of pages8
JournalEuropean Physical Journal A
Volume22
Issue number1
DOIs
Publication statusPublished - Oct 2004

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Nuclear and High Energy Physics

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