Production of η and η′ mesons via the quasi-free proton-neutron interaction.

A comparison of the close-to-threshold total cross sections for the η′ meson production in both the pp→ppη′ and pn→pnη′ reactions should provide insight into the flavour-singlet (perhaps also into gluonium) content of the η′ meson and the relevance of quark-gluon or hadronic degrees of freedom in the creation process. The excitation function for the reaction pp→ppη′ has been already established. At present, experimental investigations of the quasi-free pn→pnX reactions are carried out at the COSY-11 facility using a beam of stochastically cooled protons and the deuteron cluster target. A method of measurement and preliminary results from the test experiments of the pn→pnη reaction are presented in this report. [ABSTRACT FROM AUTHOR]