eta and eta' meson production in the quasi-free proton-neutron collisions at the COSY-11 facility


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 Reta = (sigmapn->pn eta) / (sigmapp->pp eta) close to threshold is expected to be Reta = 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-neutroncollisions 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->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.

Diploma thesis in PDF (~709kB) format