Spin triplet final state dominance in the p p ---> p n pi+ reaction at 492-MeV
May, 2001
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Abstract:
The near-forward cross section for the pp -> pn pi^+ 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-Juelich. Protons and pions emitted near zero degrees were detected in coincidence, and those with theta_pi <= 2 degrees and theta_p <= 2.5degrees 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 -> d pi^+. The smallness of the singlet contribution is consistent with trends seen in lower energy data.Note:
- 10 pages, 4 figures
- 13.75.Cs
- 25.40.Qa
- Pion production
- Final state interactions
- p p: interaction
- pi+: hadroproduction
- small-angle
- p n: final-state interaction
- spin: triplet
- p: momentum spectrum
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