Czyzykiewicz, R. (Corresponding author)FZJ*

2002
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Report No.: Juel-4017

Abstract: Both, the structure of the $\eta$' meson as well as its production mechanism are still under strong discussion and debate. The most possible hypothesis concerning the explanation of the almost three times larger mass for this meson observed experimentally relative to the theoretically calculated mass is a gluonium admixture to the $\eta$' wave function. This gluonium admixture should reflect itself in the production yield of the $\eta$' meson in proton-neutron collisions. Since the production of $\eta$' meson through the gluonium exchange is isospin independent, the ratio R$_{\nu}$ = $\frac{\sigma(pn \rightarrow pn\eta)}{\sigma(pp \rightarrow pp \eta)}$ close to threshold is expected to be R$_{\eta}$ = 1, after corrections for initial and final state interactions. The close to threshold $\eta$' production in proton-proton collisions has already been investigated at the COSY-11 facility. Cross section values in the threshold region have been measured. However, until now no data have been taken for the $\eta$' meson production in the proton-neutron collision. In order to investigate the $\eta$' production in proton-neutron collisions at the COSY synchrotron, the COSY-11 facility has been equipped with two new subsystems, namely the neutron detector and the spectator counter. The optimization of the topography for these additional detectors, the selection of the most suitable beam momentum and a discussion for the method of luminosity determination for the quasi-free pn $\rightarrow$ pn$\eta$($\eta$') reactions are presented in this thesis. Rates for the production of $\eta$ and $\eta$' mesons in proton-neutron collisions at COSY-11 have been estimated. For the calculations a special fast program has been written.

Keyword(s): COSY ; proton ; neutron ; atomic collision ; synchrotron

1. Institut 1 (Experimentelle Kernphysik I) (IKP-1)