Production of K+ and of K- mesons in heavy-ion collisions from 0.6A to 2.0A GeV incident energy

This paper summarizes the yields and the emission patterns of K⁺ and of K^- mesons measured in inclusive C+C, Ni+Ni, and Au+Au collisions at incident energies from 0.6A to 2.0A GeV using the Kaon Spectrometer KaoS at GSI. For Ni+Ni collisions at 1.5A and at 1.93A GeV as well as for Au+Au at 1.5A GeV, detailed results are presented of the multiplicities, of the inverse slope parameters, and of the anisotropies in the angular emission patterns as a function of the collision centrality. When comparing transport-model calculations to the measured K⁺ production yields, an agreement is only obtained for a soft nuclear equation of state (compression modulus K_N≈200 MeV). The production of K^- mesons at energies around 1A to 2A GeV is dominated by the strangeness-exchange reaction K^-N⇌πY (Y=Λ,Σ) which leads to a coupling between the K^- and K⁺ yields. However, both particle species show distinct differences in their emission patterns suggesting different freeze-out conditions for K⁺ and K^- mesons.