Gießen 2007 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 50: Elektromagnetische und Hadronische Sonden

HK 50.5: Talk

Thursday, March 15, 2007, 18:00–18:15, A

Energy dependence of the pp→K⁺nΣ⁺ reaction near threshold — •Yury Valdau for the ANKE collaboration — Forschungszentrum Juelich, 52425 Juelich — Petersburg Nuclear Physics Institute, Orlova Rosha, Gatchina, Russian Federation, 188300

Hyperon production in proton–proton collisions in the close-to-threshold region has been extensively studied at different experimental facilities. The energy dependence of the total cross sections for pp→K⁺pΛ and pp→ K⁺pΣ⁰ shows a phase-space behavior, though modified in the former case by the Λ p final-state interaction (FSI). However, new data on the pp→K⁺nΣ⁺ channel, published recently by the COSY-11 collaboration at excess energies of ε = 13 MeV and 60 MeV, show surprisingly high production rates [1].

Using experimental data collected at the magnetic spectrometer ANKE (COoler-Synchrotron Jülich), new estimates for the total cross section for Σ⁺ production at 129 MeV excess energy have been done. Our new results, taken in conjunction with other experimental data, would indicate a close-to-threshold anomaly in the energy dependence of the total cross section for the pp→K⁺nΣ⁺ reaction channel.

The status of analysis as well as plans for the future measurements will be presented.

Supported by FZ-Jülich, DFG, WTZ, COSY-FFE.

[1] T.Rożek et al., Phys. Lett. B 643 (2006), 251.