Kaon production from 1 to 40 A GeV

Kaon production is studied within the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) model. Results are compared with experiment and with other models. The influence of the kaon potential on the kaon azimuthal distributions at SIS energies is considered. We also discuss the role of the many-body collisions at high-density phase of reaction. Strangeness production has been a hot topic of heavy-ion studies for about 20 years. Due to strangeness conservation, kaons can not be absorbed in the nuclear medium. The kaon-nucleon scattering cross section is also quite small (∼ 10 mb). Thus, kaons deliver a signal from the high-density phase of a reaction. This property of kaons was extremely useful to extract information on the nuclear equation of state from kaon multiplicities at 1-2 A GeV [ 1, 2]. Another interesting observable at SIS energies is the kaon collective flow which is sensitive to the kaon potential. The measurements of the K + in-plane flow have been performed by the FOPI Collaboration [ 3, 4]. The analysis within the Tübingen QMD model [ 5] has revealed that the data [ 3] can be described only by using a strongly repulsive K + potential given by the Brown-Rho (BR) parametrization (U K (ρ 0) ≃ 30 MeV). Recently the KaoS Collaboration published data on K + azimuthal distributions [ 6] which were analysed in [ 7]. The strange particle and pion multiplicities have also been measured at higher energies: AGS [ 8, 9] and SPS [ 10, 11]. The most interesting observable is the K + /π + ratio plotted vs the beam energy, which has a maximum at E lab ∼ 20 A GeV (c.f. Fig. 3 below). So far, the transport models based on hadronic and string