Hyperon-nucleon effective interactions derived from modern mesonic exchange potentials

Hyperon-nucleon (YN) effective interactions are derived from the recent J{dollar}ddot u{dollar}lich one- and two-meson-exchange potentials. Based on a nucleon-nucleon (NN) G-matrix folded-diagram formalism, the YN effective interaction can be calculated in three steps. First we derive the model-space YN G matrix. Then the irreducible vertex function, namely the YN Q-box, is calculated from the G matrix. Finally the YN effective interaction, which is energy independent, is obtained by summing up a YN Q-box folded-diagram series to all orders.; A special feature of our G-matrix calculation is an essentially exact treatment of the Pauli exclusion operator Q{dollar}sb{lcub}YN{rcub}{dollar}. The presence of this operator has been a main source of difficulty for the YN G matrix in the past. To avoid this difficulty, previously one just adopted an approximation where the finite-hypernuclei Pauli exclusion operator is replaced by a nuclear-matter one with the nuclear-matter Fermi momentum treated as an adjustable parameter. This approximation is convenient but its accuracy is difficult to asess. Our Q{dollar}sb{lcub}YN{rcub}{dollar} is defined in terms of shell-model hyperon and nucleon wave functions as one should, and by way of a matrix-inversion method we have been able to treat Q{dollar}sb{lcub}YN{rcub}{dollar} exactly, except for one so-called finite-n{dollar}sb{lcub}3Lambda{rcub}{dollar} truncation. The accuracy of this truncation has been examined numerically, using the J{dollar}ddot u{dollar}lich JA and JB potentials. We have found that this truncation is quite accurate if a sufficiently large n{dollar}sb{lcub}3Lambda{rcub}{dollar} is employed. In this way we have now obtained accurate YN G matrix, starting from modern mesonic-exchange YN potentials.; Next we construct the YN {dollar} Q{dollar}-box for which we have considered valence-linked diagrams first- and second-order in the YN G interaction. Of particular interest is the YN core-polarization diagram, whose importance for the NN effective interactions is well known. This diagram provides the long-range interaction between valence baryons, and our calculations have indicated that this type of diagrams are highly important, in comparison with the bare-G interaction. Some subtle points about the strangeness exchanges for the direct and exchange core-polarization diagrams are exemplified.; The above YN {dollar} Q{dollar}-box is energy dependent, in the sense that it depends on the so-called starting energy {dollar}omega{dollar}. The final YN effective interaction is however given by a {dollar} Q{dollar}-box folded-diagram series, and the resulting effective interaction is {dollar}omega{dollar} independent. We have summed up the folded-diagram series using the Lee-Suzuki iteration method.; As a preliminary application, we have performed a {dollar}Lambda{dollar}-particle and nucleon-hole calculation for {dollar}sbsp{lcub}Lambda{rcub}{lcub}16{rcub}{dollar}O using the bare YN G-matrix interaction, and a YN {dollar} Q{dollar}-box folded-diagram calculation for {dollar}sbsp{lcub}Lambda{rcub}{lcub}18{rcub}O{dollar}. Our {dollar}sbsp{lcub}Lambda{rcub}{lcub}16{rcub}O{dollar} results are in reasonable good agreement with experiments. But for {dollar}sbsp{lcub}Lambda{rcub}{lcub}18{rcub}O{dollar} there does not seem to be any experimental data. More hypernuclear experiments are definitely needed.; We have also applied our YN folded-diagram effective interactions to a calculation of the p{dollar}sb{lcub}3/2{rcub}{dollar}-p{dollar}sb{lcub}1/2{rcub}{dollar} {dollar}Lambda{dollar} spin-orbit splitting in {dollar}sbsp{lcub}Lambda{rcub}{lcub}12{rcub}{dollar}C and {dollar}sbsp{lcub}Lambda{rcub}{lcub}16{rcub}{dollar}O. A very small splitting was found, in consistence with the experimental observations.; There is a scarcity of YN scattering data. Furthermore such scattering information consists almost exclusively of spin-averaged quantities like total and different...