The production of K+K- pairs in proton-proton collisions below the phi meson threshold

The pp -> ppK(+)K(-) reaction was measured below the phi threshold at a beam energy of 2.568 GeV using the COSY-ANKE magnetic spectrometer. By assuming that the four-body phase space is distorted only by the product of two-body final-state interactions, fits to a variety of one-dimensional distributions permit the evaluation of differential and total cross sections. The shapes of the distributions in the Kp and Kpp invariant masses are reproduced only if the K(-)p interaction is even stronger than that found at higher energy. The cusp effect in the K+K- distribution at the K-0(K) over bar (0) threshold is much more clear and some evidence is also found for coupling between the K(-)p and (K) over bar (0) n channels. However, the energy dependence of the total cross section cannot be reproduced by considering only a simple product of such pairwise final-state interactions.