A study on quark-exchange and meson-exchange in nuclear force

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The relation between two mechanisms of nuclear force,i.e.the meson exchange and the quark exchange, has been studied and a hybrid model unifying the two mechanisms has been proposed and applied to baryon-baryon interaction. A problem of vector meson exchange mechanism in generating the short-range repukion was examined in detail and it was found that only the overall attractive contribution due to the spatial components of the vector meson should be added to the quark exchange contribution. It was also found that the contributions of scalar and pseudo-scalar meson exchanges could be simply added. Based on this observation,we have made a semi-phenomenological analysis of baryon-baryon interaction in the quark cluster model supplemented by pseudo-scalar meson exchanges. Properties of the H-dibaryon were predicted and, under the condition that it existed, the nucleon-H-dibaryon interaction was also studied in the same framework. As for a relativistic quark model describing mesons and baryons in a unified way, we have chosen the Nambu-Jona-Lasinio model and first studied the baryons in a mean field approximation. The role of the six-Fermi interaction representing the chiral anomaly in stabilizing the mean field solution was clarified. We have proceeded further to solve a relativistic Faddeev equation for the baryon as a three-quark system and have obtained a preliminary solution for a simple case of quark-quark interaction only in ^1So state. The extension to a more general interaction is underway.