Threshold Production of Sigma+ at COSY-11

T.Rozek for the COSY-11-Collaboration
Institute of Physics, Silesian University, Katowice, Poland,
IKP, Forschungszentrum Jülich

At the cooler synchrotron COSY the threshold production of hyperons has been studied via the pp->pK+Lambda(Sigma0) reaction [1] resulting in a cross section ratio R = sigma(Lambda) / sigma(Sigma0) of about 28 which exceeds the ratio at high energies by an order of magnitude. Possible explanations within different models are proposed [2] but a definite conclusion is up to now not possible. Further studies in other isospin channels like the Sigma+ production will help in the clarification of the relevant dominant reaction mechanisms.

The Sigma+ production was measured at the COSY-11 installation via the pp->nK+Sigma+ reaction at Q = 13 MeV and Q = 60 MeV. COSY-11 is an internal magnetic spectrometer experiment at the COoler SYnchroton and storage ring COSY in Jülich. It is equipped with scintillator hodoscopes and drift chambers for charged particle detection and a scintillator/lead sandwich detector for neutrons.

The status of the current analysis will be presented and discussed.

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