Constraining the relativistic mean-field models from PREX-2 data: effective forces revisited

Based on the current measurement of the neutron distribution radius (R-n) of Pb-208 from the PREX-2 data, we revisited the recently developed G3 and IOPB-I force parameters by fine-tuning some specific couplings within the relativistic mean-field (RMF) model. The omega-rho-mesons coupling Lambda(omega) and the rho-meson coupling g(rho) are constrained to the experimental neutron radius of Pb-208 without compromising the bulk properties of finite nuclei and infinite nuclear matter observables. The modified parameter sets are applied to calculate the gross properties of finite nuclei such as binding energies, charge distributions, nuclear radii, pairing gaps, and single-particle energies. The root-mean-square deviations in binding energy and charge radius are estimated with respect to the available experimental data for 195 even-even nuclei, and the results compare favourably with the well-calibrated effective interactions of Skyrme, Gogny and other relativistic mean-field parametrization. The pairing gap estimations for modified G3 and IOPB-I for Sn isotopes are also compared with the Hartree-Fock-Bogoliubov calculation with the Gogny (D1S) interaction. The isotopic shift and single-particle energy spacing are also calculated and compared with the experimental data for both original and modified versions of the G3 and IOPB-I parameter sets. Subsequently, both the modified parameter sets are used to obtain the various infinite nuclear matter observables at saturation. In addition to these, the force parameters are adopted to calculate the properties of a high isospin asymmetry dense system such as neutron star matter and tested for validation using the constraint from GW170817 binary neutron star merger events. The tuned forces predict relatively good results for finite and infinite nuclear matter systems and the current limitation on the neutron radius from PREX-2. A systematic analysis using these two refitted parameter sets over the nuclear chart will be communicated shortly.

Automated summary

Based on the current experimental data and observations, the G3 and IOPB-I force parameters were re-evaluated by fine-tuning specific couplings within the relativistic mean-field model. These modified parameters were applied to calculate the properties of finite and infinite nuclear matter. The results, compared with experimental data and other parameterization methods, showed that the tuned forces have good predictive performance and meet the current limitations on neutron radius.