/ 0 31 00 26 v 1 2 7 O ct 2 00 3 Associated strangeness production in pp collisions near threshold P . Winter
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چکیده
Motivated by the ongoing discussion concerning the nature of the scalar resonances f 0 (980) and a 0 (980), the COSY-11 collaboration has taken exclusive data on the pp → ppK + K − reaction near the production threshold. A first total cross section σ = (1.80 ± 0.27 +0.28 −0.35) nb for the excess energy Q = 17 MeV has been determined. In contrary to the η, ω, and η ′ single meson production studies which clearly show the strong pp final state interaction (FSI), the cross section values obtained at COSY-11 and DISTO can be both described by a fit with a four-body phase space including the proton-proton final state interaction as well as with one-meson exchange calculations neglecting FSI effects. Therefore, one might think about a compensation of the strong pp interaction through a pK − FSI effect or an additional degree of freedom caused by the four-body final state. In the latter case, strong FSI effects can be expected at Q-values very close to the K + K − production threshold. Such a motivation triggered – in combination with the investigation of the K ¯ K interaction being relevant to the structure of the f 0 (980) – further measurements at the excess energies Q = 10 and Q = 28 MeV at COSY-11.
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