Subthreshold ϕ meson production in heavy-ion collisions

Within a BUU type transport model we study meson production in subthreshold Ni + Ni and Ru + Ru reactions. For the first time we included in our model the elementary reaction channels ρ + N, Δ → + N, π + N(1520) → + N and πρ → . In spite of a substantial increase of the multiplicities by these channels, our results stay significantly below the preliminary experimental data.