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Combined Analysis of η Meson Hadro- and Photo-production off Nucleons
K. Nakayama,오용석,H. Haberzettl 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.2
The η-meson production in photon- and hadron-induced reactions, namely, γp → pη, π^−p → nη, pp → ppη, and pn ∪ pnη, are investigated in a combined analysis in order to learn about the relevant production mechanisms and the possible role of nucleon resonances in these reactions. We consider the nucleonic, mesonic, and nucleon resonance currents constructed within an effective Lagrangian approach and compare the results with the available data for cross sections and spin asymmetries for these reactions. We found that the reaction γp → pη could be described well with the inclusion of the well-established S_(11)(1535), S_(11)(1650), D_(13)(1520), and D_(13)(1700) resonances, in addition to the mesonic current. Consideration of other well-established resonances in the same mass region, including the spin-5/2 resonances, D_(15)(1675) and F_(15)(1680), does not further improve the results qualitatively. For the reaction π_−p → nη, the P_(13)(1720) resonance is found to be important for reproducing the structure observed in the differential cross section data. Our model also improves the description of the reaction NN → NNη to a large extent compared to the earlier results by Nakayama et al. [Phys. Rev. C 68, 045201 (2003)]. For this reaction, we address two cases where either the S_(11)(1535) or the D_(13) dominates. Further improvement in the description of these reactions and the difficulty to uniquely determine the nucleon resonance parameters in the present type of analysis are discussed.