Nucleon pole contribution in thepp→ppK+K−reaction below theϕmeson threshold

Abstract

Nucleon pole contribution in the $pp\ensuremath{\rightarrow}pp{K}^{+}{K}^{\ensuremath{-}}$ reaction below the threshold of the production of the $\ensuremath{\phi}$ meson is studied within the effective Lagrangian approach. It is assumed that the ${K}^{\ensuremath{-}}p$ final state originates from the decay of the hyperons $\ensuremath{\Lambda}(1115)$ and $\ensuremath{\Lambda}(1405)$. In addition to the $pp$ final state interaction (FSI) parametrized using the Jost function, we have also considered the ${K}^{+}{K}^{\ensuremath{-}}$ FSI with the techniques of the chiral unitary approach, where the scalar mesons ${f}_{0}(980)$ and ${a}_{0}(980)$ were dynamically generated. Hence, the contributions from scalar mesons ${f}_{0}(980)$ and ${a}_{0}(980)$ occur through the ${K}^{+}{K}^{\ensuremath{-}}$ 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 ${K}^{+}{K}^{\ensuremath{-}}$. Furthermore, different forms of the couplings (pseudoscalar and pseudovector) for the $\ensuremath{\pi}NN$ interaction and different strengths for the proton-proton FSI are also investigated. It is found that the contributions from hyperons $\ensuremath{\Lambda}(1115)$ and $\ensuremath{\Lambda}(1405)$ are different between these two kinds of couplings. On the other hand, the effects of the proton-proton FSI can be adjusted by the cutoff parameters used in the form factors.