Exploring the Parameter Space of pvCD-Bonn Potentials Under Constraints from Nuclear Saturation Properties

We explore the parameter space of the pvCD-Bonn B potential within the relativistic Brueckner–Hartree–Fock framework under the constraints from the empirical saturation properties of symmetric nuclear matter. We first examined the effects of the scalar-meson and pion coupling constants. Changing the σ-meson couplings in the S01 and S13–D13 channels alone cannot reproduce the empirical saturation density and binding energy at the same time, whereas increasing gπ moves the saturation point toward the empirical region. However, changing gπ alone also affects the deuteron properties and tensor-sensitive observables. We therefore extended the parameter search by varying the ρ-meson tensor coupling fρ/gρ and readjusting the effective σ-meson couplings in the S01 and P03 channels. Four representative parameter sets with gπ2/4π=14.7–15.0 give deuteron properties close to the experimental values and maintain a reasonable description of the main neutron–proton phase shifts and differential cross sections at Elab=50 and 212 MeV. Their saturation densities lie in the range 0.159–0.161fm−3, with saturation energies between −15.00 and −15.38MeV. For the interactions obtained by varying gπ, the neutron-star mass–radius relations show only a weak dependence on the pion coupling, with maximum masses of about 2.24–2.28M⊙ and radii of about 12.3–12.6km at 1.4M⊙. These results show that including the ρ-meson tensor coupling and partial-wave-dependent σ-meson couplings provides a better balance between free-space two-nucleon observables and nuclear-matter saturation properties than varying the pion coupling alone.