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HK: Physik der Hadronen und Kerne

HK V: HV V

HK V.1: Hauptvortrag

Freitag, 24. März 2000, 10:15–10:45, H 04

Near Threshold Strangeness Production in Proton-Proton Reactions — •J. Ritman, I. Fröhlich, H.-W. Pfaff, and W. Kühn — II. Physikalisches Institut, Heinrich-Buff-Ring 16, Universität Gießen, D-35392 Gießen

A program to measure near threshold strangeness production in proton-proton reactions has been carried out by the DISTO collaboration. The production of open and hidden strangeness has been studied by exclusive measurements of the Λ and Σ hyperons, as well as ω and φ mesons, respectively. The normal spin transfer coefficient (D_NN) has been determined for exclusive hyperon production with a polarized beam. The effects are sizable and subject to simple interpretation within meson exchange models. A large negative coefficient has been observed, which is qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering. These measurements also resulted in the first observation of the φ meson near the production threshold. The observed isotropic angular distribution indicates a dominance of S-wave in the production mechanism. The φ/ω cross section ratio has been compared to predictions based on the OZI rule and on one-boson-exchange models, and its possible relation to the strangeness content of the nucleon will be discussed. The inclusive K⁻ production cross section was also determined to be about a factor 20 lower than for K⁺ mesons at the same available energy. These data and their connection to results from relativistic heavy in reactions will be presented.

This work is in part supported by GSI and IN2P3