Effective kaon masses in dense nuclear and neutron matter

The effective mass and decay width of kaonic modes in baryonic matter are studied within a coupled-channel approach based on the Chiral SU(3) Effective Lagrangian which describes all available low energy data of the coupled K̄N, πΣ, πΛ system. Including Pauli blocking and Fermi motion in the kaon dispersion relation, we find a strong non-linear density dependence of the K^- effective mass and decay width in symmetric nuclear matter at densities around 0.1 times normal nuclear matter density ρ₀ due to the in-medium dynamics of the Λ(1405) resonance. At higher densities the K^- effective mass decreases slowly but stays above 0.5 m_K at least up to densities below 3 ρ₀. In neutron matter the K^- effective mass decreases almost linearly with increasing density but remains relatively large (m*_K > 0.65 m_K) for ρ_n ≲ 3 ρ₀. The K⁺ effective mass turns out to increase very slowly with rising density.