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- Title
Systematic study of the pp $ \rightarrow$ pp $ \omega$ reaction.
- Authors
Abdel-Bary, M.; Abdel-Samad, S.; Brinkmann, K.; Clement, H.; Dietrich, J.; Doroshkevich, E.; Dshemuchadse, S.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Gast, W.; Gillitzer, A.; Gottwald, J.; Jäger, H.; Jakob, B.; Jäkel, R.; Karsch, L.
- Abstract
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 3 P1 and 1 S0 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.
- Subjects
PROTON-proton interactions; NUCLEAR reactions; HELICITY of nuclear particles; MESONS; SYNCHROTRONS
- Publication
European Physical Journal A -- Hadrons & Nuclei, 2010, Vol 44, Issue 1, p7
- ISSN
1434-6001
- Publication type
Article
- DOI
10.1140/epja/i2010-10924-0