IN-MEDIUM KAON PRODUCTION AT THE MEAN-FIELD LEVEL

The in-medium mass and energy of kaons and antikaons are studied withi n the relativistic mean-field approach compatible with kaon-nucleon sc attering data and are compared with predictions from chiral models. Im plications for the subthreshold production of kaons and antikaons in h eavy-ion collisions are discussed. On the mean-field level we find onl y small in-medium corrections for the relevant kaon production process es. The production of kaons is even less favourable at high density du e to repulsive vector interactions, We conclude that one has to go bey ond the mean-field level and take fluctuations and secondary productio n processes via resonances into account to explain the recently observ ed enhancement of kaon production at subthreshold energies. The situat ion is different for antikaons where in-medium effects strongly enhanc e their production rates. We also see strong in-medium modifications o f the absorption processes for antikaons and Lambda's which might be v isible in flow measurements. We predict that at high density the thres hold energy for antikaon and Lambda production as well as for the anni hilation become equal leading to similar numbers of antikaons and Lamb da's in the dense zone of a relativistic heavy-ion collision. (C) 1997 Published by Elsevier Science B.V.