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The kaon nuclear optical potential is studied including the effect of the Θ+ pentaquark. The one-nucleon contribution is obtained using an extension of the Jülich meson-exchange potential as bare kaon–nucleon interaction. Significant differences between a fully self-consistent calculation and the usually employed low-density Tρ approach are observed. The influence of the one-nucleon absorption process, KN→Θ+, on the kaon optical potential is negligible due to the small width of the pentaquark. In contrast, the two-nucleon mechanism, KNN→Θ+N, estimated from the coupling of the pentaquark to a two-meson cloud, provides the required amount of additional kaon absorption to reconcile with data the systematically low K+-nucleus reaction cross sections found by the theoretical models.
The width of the ω meson in cold nuclear matter is computed in a hadronic many-body approach, focusing on a detailed treatment of the medium modifications of intermediate πρ states. The π and ρ propagators are dressed by their self-energies in nuclear matter taken from previously constrained many-body calculations. The pion self-energy includes Nh and Δh excitations with short-range correlations, while the ρ self-energy incorporates the same dressing of its 2π cloud with a full 3-momentum dependence and vertex corrections, as well as direct resonance-hole excitations; both contributions were quantitatively fit to total photo-absorption spectra and πN→ρN scattering. Our calculations account for in-medium decays of type ωN→πN(⁎),ππN(Δ), and 2-body absorptions ωNN→NN(⁎),πNN. This causes deviations of the in-medium ω width from a linear behavior in density, with important contributions from spacelike ρ propagators. The ω width from the ρπ cloud may reach up to 200 MeV at normal nuclear matter density, with a moderate 3-momentum dependence. This largely resolves the discrepancy of linear T–ϱ approximations with the values deduced from nuclear photoproduction measurements.
The dynamics of strange pseudoscalar and vector mesons in hot and dense nuclear matter is studied within a chiral unitary framework in coupled channels. Our results set up the starting point for implementations in microscopic transport approaches of heavy-ion collisions, particularly at the conditions of the forthcoming experiments at GSI/FAIR and NICA-Dubna. In the K̄ N sector we focus on the calculation of (off-shell) transition rates for the most relevant binary reactions involved in strangeness production close to threshold energies, with special attention to the excitation of sub-threshold hyperon resonances and isospin effects (e.g. K̄ p vs K̄ n). We also give an overview of recent theoretical developments regarding the dynamics of strange vector mesons (K*, K̄* and ϕ) in the nuclear medium, in connection with experimental activity from heavy-ion collisions and nuclear production reactions. We emphasize the role of hadronic decay modes and the excitation of hyperon resonances as the driving mechanisms modifying the properties of vector mesons.
The dynamics of strange vector meson resonances (K* and K̄*) is investigated within the Parton-Hadron-String Dynamics (PHSD) transport approach. We present the time evolution of the production of K*− resonances from the QGP phase by quark fusion as well as from hadronic sources. We also give a brief overview of the modification of the K* through Kπ decay and K*N interaction in a hot and dense nuclear medium.