Isospin Dependence of the η′ Meson Production in Nucleon‐Nucleon Collisions

According to the quark model, the masses of η and η′ mesons should be almost equal. However, the empirical values of these masses differ by more than a factor of two. Similarly, though they have almost the same quark‐antiquark content, the total cross section for the creation of these mesons close to the kinematical thresholds in the pp → ppX reaction differs significantly. Using the COSY‐11 detection setup we intend to determine whether this difference will also be so significant in the case of the production of these mesons in the proton‐neutron scattering. Additionally, the comparison of the pp → ppη′ and pn → pnη′ total cross sections will allow to learn about the production of the η′ meson in the channels of isospin I = 0 and I = 1 and to investigate aspects of the gluonium component of the η′ meson.