Production of charged pions, kaons and antikaons in relativistic C + C andC + Au collisions

Production cross-sections of charged pions, kaons and antikaons have been m easured in C+C and C+Au collisions at beam energies of 1.0 and 1.8 AGeV for different polar emission angles. The kaon and antikaon energy spectra can be described by Boltzmann distributions whereas the pion spectra exhibit an additional enhancement at low energies. The pion multiplicity per particip ating nucleon M(pi (+))/[A(part)] is a factor of about 3 smaller in C+Au th an in C+C collisions at 1.0 AGeV whereas it differs only little for the C a nd the Au target at a beam energy of 1.8 AGeV. The Kf multiplicities per pa rticipating nucleon M(K+)/[A(part)] are independent of the target size at 1 AGeV and at 1.8 AGeV. The K- multiplicity per participating nucleon M(K-)/ [A(part)] is reduced by a factor of about 2 in C+Au as compared to C+C coll isions at 1.8 AGeV. This effect might be caused by the absorption of antika ons in the heavy target nucleus. Transport model calculations underestimate the K-/K+ ratio for C+C collisions at 1.8 AGeV by a factor of about 4 if i n-medium modifications of K-mesons are neglected.