Eta and etaprime photoproduction on the nucleon with the isobar model EtaMAID2018
Abstract.The isobar model EtaMAID has been updated with new and high precision data for $\eta$η and $\eta^{\prime}$η photoproduction on protons and neutrons from MAMI, ELSA, GRAAL and CLAS. The background is described in a recently developed Regge cut model, and for the resonance part the whole list of nucleon resonances has been investigated with 21 $N^{\ast}$N* states contributing to $\eta$η photoproduction and 12 $N^{\ast}$N* states contributing to $ \eta^\prime$η photoproduction. A new approach is discussed to avoid double counting in the overlap region of Regge and resonances. A comparison is done among four newly updated partial waves analyses for observables and partial waves. Finally, the possibility of a narrow resonance near $W = 1900$W=1900 MeV is discussed, that would be able to explain unexpected energy and angular dependence of observables in $ p(\gamma,\eta^{\prime})p$p(γ,η)p near $\eta^{\prime}$η threshold.