Strange particle production in nucleon-nucleon collisions near threshold

Polarization observables for strange particle threshold production in the processes N+N→K+Y+N (where Y is a Λ or a Σ) are studied. The spin structure of the corresponding matrix elements is derived, assuming S-wave production. Using the P invariance of the strong interaction and the Pauli principle, it is shown that these reactions can be described in terms of two (in the case of pp collisions) or three (in the case of np-collisions) independent complex amplitudes. This results in a specific behavior for polarization observables which is described. Polarization observables are calculated in the S- and P-wave approximations. In the case of collinear kinematics, relationships between spin correlation coefficients and the spin structure of the nucleon are explained.