Differential Directed Flow of K⁺ Meson within Covariant Kaon Dynamics

The collective flow of positive charged kaons in heavy ion reactions at SIS energy is investigated within the frame of covariant kaon dynamics. The theoretical results calculated by using quantum molecular dynamics show that the rapidity distribution of K⁺ mesons is more sensitive to the nuclear equation of state than the differential directed flow. The contribution of various K⁺ production reaction channels to the rapidity distribution of the K⁺ is also analysed in detail. The results indicate that the rapidity distribution ofK⁺ mesons is mainly from the contribution of the N-Δ and N-N channel. This means that the delta resonance state plays a predominantly important role for the K⁺ subthreshold production..