Generalized Dalitz plot analysis of the near-threshold pp → pp K + K − reaction in view of the K + K − final state interaction

The excitation function for the pp → ppK + K - reaction revealed a significant enhancement close to threshold that may plausibly be assigned to the influence of the pK - and K + K - final-state interactions. In an improved reanalysis of COSY-11 data for the pup → ppK + K - reaction at excess energies of Q = 10 and 28 MeV, including the proton-K - interaction, the enhancement is confirmed. Invariant mass distributions for the two- and three-particle subsystems allow us to test at low excess energies the ansatz and parameters for the description of the interaction in the ppK + K - system as derived from the COSY-ANKE data. Finally, based for the first time on the low-energy K + K - invariant mass distributions and the generalized Dalitz plot analysis, we estimate the scattering length for the K + K - interaction to be |Re(a K + K -)| = 0.5 +4.0 -0.5 fm and Im(a k+k- ) = 3.0 ± 3.0 fm.