  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 K0K0bar threshold is much more clear and some
evidence is also found for coupling between the K-p and K0bar n channels.
However, the energy dependence of the total cross section cannot be reproduced
by considering only a simple product of such pair-wise final state
interactions.
