Subthreshold phi meson production in heavy-ion collisions

Within a transport code of BUU type the production of phi mesons in the reactions Ni + Ni at 1.93 AGeV and Ru + Ru at 1.69 AGeV is studied. New elementary reaction channels rho N Delta to phi N and pi N(1520) to phi N are included. In spite of a substantial increase of the phi multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.