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HK: Physik der Hadronen und Kerne
HK 22: Plenary Session
HK 22.1: Plenarvortrag
Mittwoch, 13. März 2002, 08:30–09:00, Plenarsaal
Investigation of K+-meson production in pp and pA collisions with ANKE — •M. Büscher — Institut für Kernphysik, Forschungszentrum Jülich, 52425 Jülich
ANKE is a magnetic spectrometer located at an internal target position in one of the straight sections of COSY-Jülich. In a first series of measurements with ANKE, the production of K+-mesons in pA (A= C, Cu, Ag, Au) collisions in a wide range of beam energies, T=1.0… 2.3 GeV, has been investigated. The main experimental challenge is that far below the free NN threshold (TNN=1.58 GeV) the cross section for K+-production is extremely small, e.g. σtot = 39 nb for pC collisions at 1.0 GeV.
For the first time, the complete momentum spectrum of kaons produced at angles ϑ<12∘ was obtained for T=1.0 GeV. K+-production at this low energy requires a high degree of collectivity in the target nucleus, i.e. the number of involved nucleons must be significantly larger than one. At low kaon momenta, pK<250 MeV/c, the measured cross-section ratios for different target masses are sensitive to Coulomb and nuclear potentials in the nuclear medium. In order to obtain additional information about the reaction mechanisms leading to kaon production, measurements of correlated K+p and K+d pairs has begun.
In a recent ANKE beam time, the reaction p(2.65 GeV)p→ da0+ has been studied. The measured production cross section for the a0(980)-resonance as well as the detection of the two main a0+ decay channels (K+K0, π+η) simultaneously provide novel information about light scalar resonances. The data on pp→ pK+Y reactions from the same beam time allow to study strange hyperons with masses up to mY∼ 1.5 GeV/c2.