Production of K+ and of K− Mesons in Heavy-Ion Collisions from 0.6 to 2.0 A 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 0.6 A GeV to 2.0 A GeV using the Kaon Spectrometer KaoS at GSI. For Ni+Ni collisions at 1.5 and at 1.93 A GeV as well as for Au+Au at 1.5 A GeV detailed results of the multiplicities, of the inverse slope parameters of the energy distributions and of the anisotropies in the angular emission patterns as a function of the collision centrality are presented. 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 KN ~ 200 MeV). The production of K− mesons at energies around 1 to 2 A GeV is dominated by the strangeness-exchange reaction K−N <->pi Y (Y = Lambda, Sigma) which leads to a coupling between the K− and the K+ yields. However, both particle species show distinct differences in their emission patterns suggesting different freeze-out conditions for K+ and for K− mesons.