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Abstract

Totaland differential cross sections for the reaction $p(\ensuremath{\gamma},\ensuremath{\eta})p$ havebeen measured for photon energies in the range from 750 MeV to 3 GeV. Thelow-energy data are dominated by the ${S}_{11}$ wave which has two poles in the energy region below 2 GeV. Eleven nucleonresonances are observed in their decay into $p\ensuremath{\eta}$.At medium energies we find evidence for a new resonance $N(2070){D}_{15}$ with $(M,\ensuremath{\Gamma})=(2068\ifmmode\pm\else\textpm\fi{}22,\text{ }295\ifmmode\pm\else\textpm\fi{}40)\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}$.At $\ensuremath{\gamma}$ energiesabove 1.5 GeV, a strong peak in the forward direction develops, signalingthe exchange of vector mesons in the $t$ channel.