THE FINAL STATE INTERACTION IN THE REACTIONS pp→K+(Λp) AND pp→π+(np)

Abstract

The reactions pp→K+(Λp) and pp→π+(np) are measured with high missing mass resolution using the spectrometer BIG KARL at COSY. The pp→K+(Λp) missing mass spectrum is analyzed with respect to the final state interaction near the Λp production threshold. The observed spectrum can be described by factorizing the reaction amplitude in terms of a production amplitude and a final state enhancement factor. Parametrizing the enhancement factor in terms of the inverse Jost function allows a direct extraction of the low-energy phase-equivalent potential parameters. Constraints on the singlet and triplet scattering lengths and effective ranges can be deduced by fitting simultaneously the Λp invariant mass spectrum and the total cross section data of the free Λp scattering. A similar analysis shows that the reaction pp→π+(np) is dominated by the triplet contribution to the (np) final state interaction. An upper limit of a possible singlet contribution is deduced. Finally, the reaction pp→π+(np) allows to test the Fäldt-Wilkin extrapolation theorem where the triplet (np) continuum wave function is extrapolated to the wave function of the deuteron.