Kaon and Antikaon Production in Heavy Ion Collisions at 1.5 AGeV

At the Kaon Spectrometer KaoS at SIS, GSI the production of kaons and antikaons in heavy ion reactions at a beam energy of 1.5 AGeV has been measured for the collision systems Ni+Ni and Au+Au. The K-/K+ ratio is found to be constant for both systems and as a function of impact parameter but the slopes of K+ and K- spectra differ for all impact parameters. Furthermore the respective polar angle distributions will be presented as a function of centrality.