Analysis of the reaction γ p → η^' p

The production of η^' mesons in the reaction γ p→ pη^' is described within a relativistic meson exchange model of hadronic interactions. This process can be described quite well over the entire energy range of available data by considering an S_11 and a P_11 resonance, in addition to the t-channel mesonic current. The observed angular distribution is due to the interference between the t-channel and the nucleon resonance s- and u-channel contributions. Our analysis yield a position close to 1650 MeV and 1870 MeV for the S_11 and P_11 resonance, respectively. Although it is tempting to identify them with the known S_11(1650) resonance and the missing P_11 resonance predicted at 1880 MeV, respectively, the reasons why such an identification from the present analysis is still premature are presented. The nucleonic current is found to be relatively small and that the NNη^' coupling constant cannot be much larger than g_NNη^'=3.