Probing dense matter with strangeness production in nuclear collisions

Experiments on strangeness production in nucleus–nucleus collisions at SIS energies address fundamental questions of modern nuclear physics: the determination of the nuclear equation-of-state at high baryon densities and the properties of hadrons in dense nuclear matter. From the yields of K⁺ mesons measured in heavy-ion collisions a value for the nuclear compressibility of is extracted for nuclear densities around twice saturation density using different microscopic transport models. Both the yield of K⁺ mesons and their anisotropic azimuthal angular distribution (elliptic flow) exhibit strong evidence for a repulsive K⁺N potential. The yields of K⁺ and K⁻ mesons measured in proton–nucleus collisions can be reproduced by transport calculations assuming at saturation density a repulsive K⁺N potential of and an attractive K⁻N potential of .