ORIGIN OF SUBTHRESHOLD K-ION COLLISIONS( PRODUCTION IN HEAVY)

We investigate the origin of subthreshold K+ production in heavy ion c ollisions at intermediate energies. In particular we study the influen ce of the pion induced K+ creation processes. We find that this channe l shows a strong dependence on the size of the system, i.e., the numbe r of participating nucleons as well as on the incident energy of the r eaction. In an energy region between I and 2 GeV/nucleon the pion indu ced processes essentially contribute to the total yield and can even b ecame dominant in reactions with a large number of participating nucle ons. Thus we are able to reproduce recent measurements of the KaoS Col laboration for I GeV/nucleon Au on Au reactions adopting a realistic m omentum dependent nuclear mean field.