M. Fritsch

Production of ω mesons in proton–proton collisions

The cross section for the production of

Measurement of the eta production in proton proton collisions with the COSY time-of-flight spectrometer

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Influence of N*-resonances on hyperon production in the channel pp->K+ Lambda p at 2.95, 3.20 and 3.30 GeV/c beam momentum

mesons in proton-proton collisions has been measured in a previously unexplored region of incident energies. Cross sections were extracted at 92 MeV and 173 MeV excess energy, respectively. The angular distribution of the

Two-pion production in proton-proton collisions with a polarized beam

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Comparison of isoscalar vector meson production cross sections in proton–proton collisions ☆

at

Proton proton bremsstrahlung at 797 MeV/c

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Systematic study of the pp

=173 MeV is strongly anisotropic, demonstrating the importance of partial waves beyond pure s-wave production at this energy.

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Abstract:The reaction pp → ppη was measured at excess energies of 15 and 41 MeV at an external target of the Jülich Cooler Synchrotron COSY with the time-of-flight spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process ppη were detected with an acceptance of nearly 100% and the η was reconstructed by the missing-mass technique. For both excess energies the angular distributions are found to be nearly isotropic. In the invariant-mass distributions strong deviations from the pure phase space distributions are seen.

pp

Abstract Hyperon production in the threshold region was studied in the reaction pp → K + Λ p using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at the three different beam momenta of p beam = 2.95 , 3.20 and 3.30 GeV/ c , corresponding to excess energies of e = 204 , 285 and 316 MeV, respectively. Total cross-sections were deduced for the three beam momenta to be 23.9 ± 0.8 ± 2.0 μb , 28.4 ± 1.3 ± 2.2 μb and 35.0 ± 1.3 ± 3.0 μb . Differential observables including Dalitz plots were obtained. The analysis of the Dalitz plots reveals a strong influence of the N ( 1650 ) -resonance at p beam = 2.95 GeV / c , whereas for the higher momenta an increasing relative contribution of the N ( 1710 ) - and/or of the N ( 1720 ) -resonance was observed. In addition, the pΛ -final-state interaction turned out to have a significant influence on the Dalitz plot distribution.

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The two-pion production reaction pp → ppπ+π− was measured with a polarized proton beam at Tp ≈ 750 and 800MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for Quirl and central calorimeter provided positive π+ identification in addition to the standard particle identification, energy determination as well as time-of-flight and angle measurements. Thus all four-momenta of the emerging particles could be determined with 1–4 overconstraints. Total and differential cross-sections as well as angular distributions of the vector analyzing power have been obtained. They are compared to previous data and theoretical calculations. In contrast to predictions we find significant analyzing-power values up to Ay = 0.3. The data taken in the energy region of the excitation of the Roper resonance confirm that its dominant ππ decay channel is N* → Nσ.