Effective and Definite Resonances in the Photoproduction of η′ Mesons on Protons

A qualitative description of the most accurate experimental differential cross sections of the reaction γp→η′p from the CLAS 2009 Collaboration and unprecedentedly accurate total cross sections of this reaction, measured by the A1 Mainz 2015 Collaboration in the isobaric model of photoproduction has been obtained. Masses and widths of four resonances, extracted from such fits, lay claim to a real existence and lie in the usual mass and width intervals of nucleon resonances. But in order for our model not to contradict the results of measurements of the Σ-asymmetry of this reaction made by the GRAAL 2013 Collaboration, the need arose for an additional resonance with mass equal to the threshold of the reaction under discussion, and width Γ = 110 MeV.