Wei-Dong Sun

Scalar-isoscalar meson exchange in the calculation of the nucleon-nucleon interaction

We provide a unified description of (i) scalar-isoscalar exchange in the nucleon-nucleon interaction, (ii) the pion-nucleon sigma term, and (iii) the scalar form factor of the nucleon. Our analysis requires that we specify a parameter that appears in the description of a nucleon valence-quark {open_quotes}core.{close_quotes} Other parameters are fixed either by our analysis of the Nambu{endash}Jona-Lasinio model, or with reference to a recent lattice simulation of QCD in which the scalar form factor of the nucleon was calculated. We find that our model has some predictive power. Once the parameters are fixed, we find that we reproduce the values of the scalar form factor of the nucleon, as determined in the lattice simulation. We also predict the strength of the scalar-isoscalar {ital NN} potential for the particular one-boson-exchange model considered here, where the effects of (virtual) {Delta} excitation are treated in an explicit fashion. However, the overall strength of the force obtained in this work is sensitive to the approximations used in the calculation. {copyright} {ital 1997} {ital The American Physical Society}

SCALAR-ISOSCALAR CORRELATOR IN A PHENOMENOLOGICAL COUPLED-CHANNEL QUARK MODEL

We calculate the Fourier transform of the scalar-isoscalar correlator making use of a generalized coupled-channel Nambu-Jona-Lasinio (NJL) model. The calculation is based upon the assumption that the correlator may be calculated by inserting two-pion continuum states between the operators and . We introduce a model for confinement such that the various quark-loop integrals only have cuts due to the physical two-pion continuum thus allowing us to construct dispersion relations for the correlator. It is then shown that for spacelike P2(P2 0.