K and K* Exchange Effects in Lambda Hypernuclei

We study the effects of K and K*exchange between the Λ hyperon and the nucleon in a Λ hypernucleus, where the nuclear core is described by a successful relativistic mean-field (RMF) model. In general, K and K* are responsible for strangeness exchange in the one-boson-exchange potential model, which are absent in the RMF calculation. We investigate the contribution of Fock terms derived from K and K* exchange. We use a pseudovector coupling for K exchange, which is found to provide a repulsive potential for the Λ particle in hypernuclei. Both vector and tensor couplings for K* exchange are taken into account, whose combined effect on the Λ single-particle energy is found to be small.