The long mean free path of K + mesons in nuclear matter makes this particle a suitable messenger for the dynamics of nucleus-nucleus reactions at intermediate energies (100 MeV to 3 GeV per nucleon). A prerequisite for this is the knowledge of the elementary production cross sections πN → ΣK. Here these cross sections are studied for the first time with the explicite inclusion of the rel (1 − ) vector meson exchange is included. It is shown that the total cross sections for different channels of the πN → ΣK reactions, i.e. π + p → Σ + K + , π − p → Σ − K + , π + n → Σ 0 K + (π − p → Σ − K + ) and π 0 p → Σ 0 K + differ not only by absolute values but also by their energy dependence. This shape differences are due to the mixture of the isospin I = 3/2 ∆(1920) with isospin I = 1/2 nucleon resonances. However, this I = 3/2 resonance does not give a contribution to the πN → ΛK reactions. So the shapes of the total cross sections πN → ΛK for different isospin projections are the same. In spite of this, such cross sections averaged over different isospin projections in the same multiplet are often used for studies of kaon production in heavy-ion collisions. Here we give an explicit separate parametrization of the cross sections for each channel πN → ΣK, which are calculated in this work. The total cross section for π − p → Σ − K + which runs through different I = 3/2 and I = 1/2 resonances can be well reproduced by the present model. * Supported by DFG under contract No. Fa 67/14-1 † Supported by GSI under contract No. 06 TÜ 736 0 Because kaons (K + ) have a long mean free path inside the nucleus, one believes that they are good messengers to provide information about the high density and temperature phase of the heavy ion collisions [1,2]. Furthermore, they can be also sensitive probes for the nuclear equation of state (EOS) [3]. For these reasons, many studies of kaon production in heavy ion collisions have been performed both theoretically and experimentally [1]- [13].In most theoretical studies of the kaon production in heavy ion collisions by either the Vlasov-Uehling-Uhlenbeck approach (VUU) [4], or by "quantum" molecular dynamics (QMD) [5,6], however, the kaon elementary production cross sections in free space parametrized by J. Randrup and C. M. Ko [12] for B 1 B 2 → B 3 Y K, and by J. Cugnon and R. M. Lombard [13] for πN → Y K are widely used. Here B stands for either the nucleon or the ∆(1232), Y stands for either the Σ or the Λ, respectively. Although there exists a relatively long history for kaon production studies, not many investigations have been performed for the elementary process [14].On the other hand, due to recent high precision data, we have now rich and accurate informations on the baryon resonances, on quantum numbers, on decay modes, on decay rates and so on [15,16]. Thus, it is now adequate and necessary to incorporate these resonances in calculations of the elementary cross section for kaon production. There are some works which include such baryon resonances in kaon production stu...

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Heavy-ion collisions at intermediate energies are studied by using a new relativistic quantum molecular dynamics (RQMD) code, which is a covariant generalization of the quantum molecular dymanimcs (QMD) approach. We show that this new implementation is able to produce the same results in the nonrelativistic limit (i.e., 50 MeV/nucleon) as the noncovariant QMD. Such a comparison is not available in the literature. At higher energies (i.e. , 1.5 GeV/nucleon and 2 GeV/nucleon) RQMD and QMD give difFerent results in respect to the time evolution of the phase space, for example for the directed transverse How. These differences show that consequences of a covariant description of heavy-ion reactions within the framework of RQMD exist even at intermediate energies.PACS number(s): 25.70.z, 24.10.3v, 02.70.Ns

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Parametrizations of total cross sections sucient for all channels of the πB → Y K reactions are completed using a resonance model. As well as discussing the πN → ΛK reactions, which were not presented in our previous publications, we present the differential cross section for πN → ΛK. This report also aims at presenting supplementary discussions to our previous work.

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