Last year, for the first time total cross section measurements
in the proton-proton collision close to the reaction
threshold of the eta' meson production have been published
Two independent experiments performed at the accelerators SATURNE
and COSY have consistent results.
At a given excess energy the determined values of the total cross
sections for the eta' meson production are about a factor
of fifty smaller than the corresponding ones for the eta
This observation rather excludes a resonant production of the
eta' meson in the threshold region, whereas, such a
mechanism dominates the close to threshold creation of meson
The quark content of both these mesons is very similar, however, due to the small pseudoscalar mixing angle (ThetaPS ~ -15°) , the eta' meson is predominantly a flavour singlet state and is expected to contain a significant admixture of gluons. This possibility makes a comparative study of eta and eta' mesons very interesting.
Detailed investigations of the production mechanism and of the proton-eta and proton-eta' interaction constituted the motivation for the further precise measurements of the eta' meson production performed with a stochastically cooled proton beam, and of the eta meson production performed with a beam momentum changed continuously during each cycle of data taking .
Results of these new measurements carried out by the COSY-11 detection system at the COSY accelerator will be presented and discussed.
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Publication: Conference Proceedings 512, Melville, NY, 2000, ISBN 1-56396-928-9, p.65-78