Final-state interactions in the process pp → pK + Λ

The possibility to determine the pΛ scattering length from the final-state interaction in the reaction � → pK + Λ is investigated experimentally. From a transversely polarized measurement, the K + analyzing power (AN ) which, in principle, allows one to extract the spin triplet scattering length is studied. An unexpected energy dependence of the forward/backward symmetric part of AN is found. The influence of N ∗ resonances on the pΛ invariant mass spectrum is investigated by exploiting the large acceptance for the process � → pK + Λ → pK + pπ − and is found to be the main source of uncertainty for determining the pΛ scattering length.