Hyperon production in near-threshold nucleon-nucleon collisions

Abstract

We study the mechanism of the associated \ensuremath{\Lambda}-kaon and \ensuremath{\Sigma}-kaon production in nucleon-nucleon collisions over an extended range of near-threshold beam energies within an effective Lagrangian model, to understand the new data on $\mathit{pp}\ensuremath{\rightarrow}p\ensuremath{\Lambda}{K}^{+}$ and $\mathit{pp}\ensuremath{\rightarrow}p{\ensuremath{\Sigma}}^{0}{K}^{+}$ reactions published recently by the COSY-11 Collaboration. In this theory, the hyperon production proceeds via the excitation of ${N}^{*}(1650),{N}^{*}(1710)$, and ${N}^{*}(1720)$ baryonic resonances. Interplay of the relative contributions of various resonances to the cross sections is discussed as a function of the beam energy over a larger near threshold energy domain. Predictions of our model are given for the total cross sections of $\mathit{pp}\ensuremath{\rightarrow}p{\ensuremath{\Sigma}}^{+}{K}^{0},\mathit{pp}\ensuremath{\rightarrow}n{\ensuremath{\Sigma}}^{+}{K}^{+}$, and $\mathit{pn}\ensuremath{\rightarrow}n\ensuremath{\Lambda}{K}^{+}$ reactions.