Author/Authors :
V Abaev، نويسنده , , M Büscher، نويسنده , , S. Dymov، نويسنده , , M Hartmann، نويسنده , , A Kacharava، نويسنده , , V.I. Komarov، نويسنده , , V Koptev، نويسنده , , V Kurbatov، نويسنده , , S. Mikirtychiants، نويسنده , , M Nekipelov، نويسنده , , A Petrus، نويسنده , , H Str?her، نويسنده , , Yu.N Uzikov، نويسنده , , C Wilkin، نويسنده , , S Yaschenko، نويسنده ,
Abstract :
The near-forward cross section for the pp→pnπ+ reaction has been measured at 492 MeV by using the large acceptance ANKE magnetic spectrometer placed at an internal target position of the storage ring COSY-Jülich. Protons and pions emitted near zero degrees were detected in coincidence, and those with θπ⩽2° and θp⩽2.5° were subjected to detailed analysis. Under these conditions, the excitation energy in the np system was below 3 MeV over the measured momentum range. This is the region of the np final-state-interaction peak, which was measured with a resolution of a fraction of an MeV. The shape of the peak allows one to conclude that the fraction of final spin-singlet np pairs is below about 10%. By using the results of scattering theory, this limit is confirmed through a comparison with the cross section for pp→dπ+. The smallness of the singlet contribution is consistent with trends seen in lower energy data.
