Within a transport code of BUU type the production of φ mesons in the reactions Ni + Ni at 1.93 A·GeV and Ru + Ru at 1.69 A·GeV is studied. New elementary reaction channels ρN(∆) → φN and πN(1520) → φN are included. In spite of a substantial increase of the φ multiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

Dalitz decay of baryon resonances is studied and expressions for the decay width are derived for resonances with arbitrary spin and parity. Contributions of the various terms in the transition matrix element are compared and relevance of spin-parity and the resonance mass is discussed. Explicite algebraic expressions are cited for spin≤5/2 resonances. The results can be used in models of dielectron production in elementary reactions and heavy ion collisions.

We study three-flavor octet baryons by using the so-called extended Linear Sigma Model (eLSM). Within a quark-diquark picture, the requirement of a mirror assignment naturally leads to the consideration of four spin-1 2 baryon multiplets. A reduction of the Lagrangian to the two-flavor case leaves four doublets of nucleonic states which mix to form the experimentally observed states N (939), N (1440), N (1535) and N (1650). We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of the aforementioned states. By tracing their masses when chiral symmetry is restored, we conclude that the pairs N (939), N (1535) and N (1440), N (1650) form chiral partners.

Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction πN → N e + e − . We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the N (1520) and N (1440) resonances, which are essential at the collision energy of the recent data obtained by the HADES collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unravelling the resonance contributions to this process.