Darmstadt 2008 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 35: Elektromagnetische und Hadronische Sonden

HK 35.7: Talk

Thursday, March 13, 2008, 18:15–18:30, 1C

Energy dependence of the pp→K⁺nΣ⁺ reaction near threshold — •Yury Valdau for the ANKE collaboration — Forschungszentrum Juelich, Institut fuer Kernphysik*, Germany, D-52425 Jülich

In contrast to reactions with production of neutral light hyperons (Λ and Σ⁰) the energy dependence of the pp → K⁺ n Σ⁺ reaction shows a surprising behavior in close-to-threshold region (T_p ≈ 1.79 GeV). Due to strangeness conservation below threshold of the pp → K⁺ n Λ π⁺ process there is no other source of the K⁺ π⁺ events, thus events from genuine Σ⁺ production can be identified by K⁺ π⁺ coincidence without using a neutron detector.

The energy dependence of the Σ⁺ production total cross section has been studied at four energies between threshold and ∼ 2.0 GeV using the magnetic spectrometer ANKE-COSY. In the experimental data the contribution of Σ⁺ production to three simultaneously measured experimental spectra (K⁺ inclusive, K⁺ p and K⁺ π⁺ correlation spectra) can be identified. Thus, total cross sections of the process will be determined using the ratio to other well known hyperon production channels or absolute normalization.

The status of analysis as well as preliminary experimental results will be presented.

Supported by the COSY–FFE program.