SUBTHRESHOLD ANTIKAON PRODUCTION IN NUCLEUS-NUCLEUS COLLISIONS

Antikaon production in nucleus-nucleus collisions at energies below th e threshold for its production from the nucleon-nucleon interaction in free space is studied in the relativistic transport model. We include the in-medium self-energies of kaon and antikaon determined from eith er the mean-field approximation to the chiral Lagrangian or the empiri cal effective scattering lengths for the kaon-nucleon and the antikaon -nucleon interaction. Also, the final-state interactions of antikaons with nucleons through both elastic scattering and absorption are expli citly treated in the study. Our results indicate that an attractive sc alar potential for kaon and antikaon is needed to explain quantitative ly the experimental data from the Ni+Ni collision at 1.85 GeV/nucleon. To see more clearly the effect of the attractive scalar potential, we suggest that experiments at lower incident energies be carried out.