Coupled-channel effects in the pp→ppK+K−pp→ppK+K− reaction

The cross sections for the pp→ppK+K−pp→ppK+K− reaction were measured at three beam energies 2.65, 2.70, and 2.83 GeV at the COSY-ANKE facility. The shape of the K+K−K+K− spectrum at low invariant masses largely reflects the importance of KK¯ final state interactions. It is shown that these data can be understood in terms of an elastic K+K−K+K− rescattering plus a contribution coming from the production of a K0K¯0 pair followed by a charge-exchange rescattering. Though the data are not yet sufficient to establish the size of the cusp at the K0K¯0 threshold, the low mass behaviour suggests that isospin-zero production is dominant.