CREX- and PREX-II-motivated relativistic interactions and their implications for the bulk properties of nuclear matter and neutron stars

We investigate the implications of parity-violating electron scattering experiment on neutron skin thickness of ${}^{48}\mathrm{Ca}$ [calcium radius experiment (CREX)] and ${}^{208}\mathrm{Pb}$ [lead radius experiment (PREX-II)] data on the bulk properties of finite nuclei, nuclear matter, and neutron stars. The neutron skin thickness from the CREX and PREX-II data is employed to constrain the parameters of relativistic mean-field models which includes different nonlinear, self- and cross-couplings among isoscalar-scalar $\sigma$, isoscalar-vector $\omega$, isovector-scalar $\delta$, and isovector-vector $\rho$ meson fields up to the quartic order. Three parametrizations of RMF model are proposed by fitting CREX, PREX-II, and both CREX as well as PREX-II data to assess their implications. A covariance analysis is performed to assess the theoretical uncertainties of model parameters and nuclear matter observables along with correlations among them. The RMF model parametrization obtained with the CREX data acquires much smaller value of symmetry energy ($J=28.97\pm 0.99$ MeV) and its slope parameter ($L=30.61\pm 6.74$ MeV) in comparison to those obtained with PREX-II data. The neutron star properties are studied by employing the equations of state composed of nucleons and leptons in $\beta$ equilibrium.

Figure 1

Correlation coefficients among the model parameters of the Lagrangian given by Eq. (1) for BSRV-CREX parametrization.

Figure 2

Same as Fig. 1 but for BSRV-PREX parametrization.

Figure 3

Same as Fig. 1 but for for BSRV-CPREX parametrization.

Figure 4

Variation of neutron skin thickness predicted for the nuclei considered in the fit data as a function of asymmetry parameter ($\delta$). The shaded region is calculated by using Eq. (19).

Figure 5

Variation of Pressure as a function of baryon density for symmetric nuclear matter (SNM) computed with BSRV's parametrizations along with NL3, IOPB-1, FSUGarnet, and Big Apple models. The shaded region represents the experimental data taken from the reference [28].

Figure 6

Variation of Pressure as a function of baryon density for pure neutron matter (PNM) computed with BSRV's parametrizations along with NL3, IOPB-1, FSUGarnet, and Big Apple models. The shaded region represents the experimental data taken from the reference [28].

Figure 7

Variation of density dependence of symmetry energy ($L$) as a function of baryon density for various parametrizations considered in the present work.

Figure 8

EoSs, i.e., pressure as a function of energy density for $\beta$-stable equilibrated nuclear matter for various parametrizations. The shaded region represents the observational constraints reported in Ref. [57].

Figure 9

The plot of proton fractions as a function of baryon density. The dotted horizontal line represents the threshold for the direct Urca process, i.e., $({\rho }_p/\rho )$ = 0.11 [58].

Figure 10

Variation of the gravitational mass of nonrotating neutron stars as a function of radius. for BSRV's parametrizations. The results for NL3, IOPB-1, FSUGarnet, and Big Apple parameter sets are also shown.

Figure 11

Variation of dimensionless tidal deformability ($\mathrm{\Lambda }$) with respect to gravitational mass for all BSRV's parametrizations. The results for NL3, IOPB-1, FSUGarnet, and Big Apple parameter sets are also shown.

Figure 12

The thresholds for the onset of direct Urca Process in neutron stars. The threshold density is represented by the solid black circles and the corresponding neutron star mass for such central density is depicted by solid magenta squares.

Figure 13

Correlation coefficients amongst neutron star observables as well as the bulk properties of nuclear matter at the saturation density and model parameters for BSRV-CREX parametrization.

Figure 14

Same as Fig. 13, but for BSRV-PREX paramerization.

Figure 15

Same as Fig. 13 but for BSRV-CPREX paramerization.