Verlag des Forschungszentrums Jülich
JUEL-4243
Czyzykiewicz, Rafal
Study of the production mechanism of the n meson in proton-proton collisions by means of analysing power measurements
106 S., 2007
The analysing power measurements for the pp -> ppη reaction studied in this
dissertation are used in the determination of the reaction mechanism of the η
meson production in nucleon-nucleon collisions.
Measurements have been performed in the close-to-threshold energy region at
beam momenta of pbeam = 2.010 and 2.085 GeV/c, corresponding to the excess
energies of Q = 10 and 36 MeV, respectively. The experiments were realised by
means of a cooler synchrotron and storage ring COSY along with a cluster jet
target. For registration of the reaction products the COSY-11 facility has been
used. The identification of the η meson has been performed with the missing mass
method.
The results for the angular dependence of the analysing power combined with
the hitherto determined isospin dependence of the total cross section for the η
meson production in the nucleon-nucleon collisions, reveal a statistically signifi-
cant indication that the excitation of the nucleon to the S11 resonance, the process
which intermediates the production of the η meson, is predominantly due to the
exchange of a η meson between the colliding nucleons.
The determined values of the analysing power at both excess energies are
consistent with zero implying that the η meson is produced predominantly in the
s-wave at both excess energies.
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