In-medium kaon-nucleon vector interaction based on chiral effective Lagrangian

We investigate the implications of the four-nucleon terms in the chiral eff ective Lagrangian for the s-wave K-nucleon effective interaction. We nd tha t such terms play a nontrivial role in the description of symmetric nuclear matter. Our results for the kaon effective energy and in-medium K+- nucleo n scattering are in agreement with the previous prediction obtained by in-m edium scaling qualitatively.