Open and Hidden Strangeness Production in Nucleon-Nucleon Collisions
  We present an overview of the description of K and eta meson productions in nucleon-nucleon collisions within an effective Lagrangian model where meson production proceeds via excitation, propagation and subsequent decay of intermediate baryonic resonant states. The $K$ meson contains a strange quark ($s$) or antiquark ($\bar s$) while the $\eta$ meson has hidden strangeness as it contains some component of the $s{\bar s}$ pair. Strange meson production is expected to provide information on the manifestation of quantum chromodynamics in the non-perturbative regime of energies larger than that of the low energy pion physics. We discuss specific examples where proper understanding of the experimental data for these reactions is still lacking. 
Radhey Shyam