Kaon and pion production in relativistic heavy-ion collisions

The Boltzmann-Uehling-Uhlenbeck (BUU) transport model is applied to study strangeness and pion production in nucleus-nucleus collisions. Starting from proton induced reactions, we further investigate Si+Au, Au+Au, and Pb+Pb collisions in the energy range between 2 and 40A GeV and compare the results with data and other transport calculations. The q (q) over bar -annihilation, or resonance, channel simulated by the string model in meson-nucleon collisions at root s > 2 GeV is introduced. The importance of this channel for a good description of the proton-nucleus data on K+ production is demonstrated. We further show that meson-meson collisions contribute significantly to the K (K) over bar production in heavy-ion collisions above 5 A GeV and improve the agreement with data on the K+/pi(+) ratio. Finally, we study the influence of in-medium modifications of the FRITIOF model on pion and kaon production.