Total and differential cross sections for the dp→He3η reaction have been measured near threshold for He3 center-of-mass momenta in the range from 17.1 MeV/c to 87.5 MeV/c. The data were taken during ...a slow ramping of the COSY internal deuteron beam scattered on a proton target detecting the He3 ejectiles with the COSY-11 facility. The forward–backward asymmetries of the differential cross sections deviate clearly from zero for center-of-mass momenta above 50 MeV/c indicating the presence of higher partial waves in the final state. Below 50 MeV/c center-of-mass momenta a fit of the final state enhancement factor to the data of the total cross sections results in the He3–η scattering length of |a|=4.3±0.5 fm.
Measurements of the analyzing power for the p-vectorp{yields}pp{eta} reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with ...zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the {eta} meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S{sub 11}(1535) resonance is predominantly due to the exchange of the {pi} meson between the colliding nucleons.
We have measured excitation functions for the
dp
→
3He
X, (
X
=
π
0
,
η
) channels near the
η production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam ...scattered on a proton target. The excitation function for the reaction
dp
→
3He
π
0 does not show any structure which could originate from the decay of
3He–
η bound state. We measured also the threshold excitation curve for the
dp
→
3He
X process, however, contrary to the SATURNE results, we observe no cusp near the
η threshold.
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