Mean field and pairing properties of nuclear matter in a quark–meson coupling model Original Research Article

We investigate the effects on mean-field quantities and nuclear pairing in symmetric nuclear matter of the density-dependent effective nucleon–scalar-meson coupling that is obtained in a σ–ω quark–meson coupling model. We find that the effective coupling strongly modifies mean-field quantities, such as the compressibility, the effective nucleon mass, and the spin–orbit interaction, as well as the scalar and vector components of the pairing field, but that it leaves the nonrelativistic pairing gap function almost unchanged. This model independence is due in part to the strong constraint imposed by requiring that the pairing field reproduce the two-nucleon virtual state in the vacuum, but is also a result of compensation between variations in the effective nucleon–scalar-meson coupling constant and the effective nucleon mass. We also analyze the correlation between the compressibility and the spin–orbit interaction and find that neither our model nor other quark–meson coupling models can describe the two simultaneously.