Differential cross sections for γp→ηp have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass ~1.8 GeV couples to the ηN channel.
Physical Review Letters
Dugger, M.; Biselli, Angela; and CLAS Collaboration, "η Photoproduction on the Proton for Photon Energies from 0.75 to 1.95 GeV" (2002). Physics Faculty Publications. 101.
M. Dugger et al. [CLAS Collaboration], "η Photoproduction on the Proton for Photon Energies from 0.75 to 1.95 GeV", Physical Review Letters 89, 222002 (2002) [Erratum-ibid. 89, 249904 (2002)]. DOI: 10.1103/PhysRevLett.89.222002