Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 49: Hadronic Probes V, Particle Production

HK 49.4: Group Report

Wednesday, March 18, 1998, 15:15–15:45, C

η and η ′ Production in pp-Reactions at 2.85 GeV — •H.-W. Pfaff, A. Brenschede, I. Fröhlich, W. Kühn, and J. Ritman — II. Physikalisches Institut Universität Gießen

The large mass of the η′-meson relative to the η-meson is not understood in terms of quark and gluonic degrees of freedom. Within the various speculative models to explain this mass anomaly different couplings to the nucleon might be expected. The relative production cross sections of η and η′ in pp-collisions could contribute significantly to clarify this issue. Therefore the DISTO spectrometer has been used to measure η and η′ production in pp-reactions at 2.85 GeV (144 MeV above the η′-threshold).

The DISTO detector system at SATURNE is a magnetic spectrometer built for the investigation of exclusive hyperon- and meson- production in pp-reactions. Scintillating fibers are located in a 1.47 T dipol field followed by MWPCs for particle tracking. Plastic scintillating hodoscopes and water Cherenkov detectors allow π, K and p particle identification. We investigated the kinematicle complete reactions pp → ppη → ppπ⁺π⁻π⁰ (π⁰ missing) and pp → ppη′ → ppπ⁺π⁻η ( η → neutral decay modes).

The measured η / η′- ratio will be discussed in comparison with various model predictions.

⋆ supported by IN2P3 and GSI.