Calculations of K± and ϕ production in near-threshold proton-nucleus collisions

K± and ϕ meson production in proton-nucleus (pA) collisions has been calculated within a BUU transport model. It is shown that the nucleon-hyperon strangeness transfer channel is essential. The role of three-body reactions has been investigated within the medium. The target mass dependence of ϕ production is predicted to give important information on the in-medium properties of all three mesons.