Nucleon pole contribution in the pp→ ppK+K- reaction below the ϕ meson threshold

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Nucleon pole contribution in the pp→ ppK+K- reaction below the threshold of the production of the ϕ meson is studied within the effective Lagrangian approach. It is assumed that the K- p final state originates from the decay of the hyperons Λ(1115) and Λ(1405). In addition to the pp final state interaction (FSI) parametrized using the Jost function, we have also considered the K+K- FSI with the techniques of the chiral unitary approach, where the scalar mesons f₀(980) and a₀(980) were dynamically generated. Hence, the contributions from scalar mesons f₀(980) and a₀(980) occur through the K+ K- FSI. It is shown that the available experimental data are well reproduced, especially the total cross sections and the invariant mass distributions of pp and K+K-. Furthermore, different forms of the couplings (pseudoscalar and pseudovector) for the πNN interaction and different strengths for the proton-proton FSI are also investigated. It is found that the contributions from hyperon Λ(1115) and Λ(1405) are different between these two kinds of couplings. On the other hand, the effects of the proton-proton FSI can be adjusted by the cut off parameters used in the form factors.