A systematic study of the production of \( \omega\) -mesons in proton-proton collisions was carried out in a kinematically complete experiment at three excess energies ( \( \varepsilon\) = 92, 128, 173 MeV). Both protons were detected using the large-acceptance COSY-TOF spectrometer at an external beam line at the Cooler Synchrotron COSY at Forschungszentrum Jülich. The total cross-section, angular distributions of both \( \omega\) -mesons and protons were measured and presented in various reference frames such as the overall CMS, helicity and Jackson frame. In addition, the orientation of the \( \omega\) -spin and invariant-mass spectra were determined. We observe \( \omega\) -production to take place dominantly in Ss and Sp final states at \( \varepsilon\) = 92, 128 MeV and, additionally, in Sd at \( \varepsilon\) = 173 MeV. No obvious indication of resonant \( \omega\) -production via N*-resonances was found, as proton angular distributions are almost isotropic and invariant-mass spectra are compatible with phase space distributions. A dominant role of 3P1 and 1S0 initial partial waves for \( \omega\) -production was concluded from the orientation of the decay plane of the \( \omega\) -meson. Although the Jackson angle distributions in the \( \omega\) p-Jackson frame are anisotropic we argue that this is not an indication of a resonance but rather a kinematical effect reflecting the anisotropy of the \( \omega\) angular distribution. The helicity angle distribution in the \( \omega\) p-helicity frame shows an anisotropy which probably reflects effects of the \( \omega\) angular momenta in the final state; this observable may be, in addition to the orientation of the \( \omega\) decay plane, the most sensitive one to judge the validity of theoretical descriptions of the production process.
Angular Distribution Dalitz Plot Phase Space Distribution Helicity Angle Decay Plane
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