Can the PREX-2 and CREX results be understood by relativistic mean-field models with the astrophysical constraints?

TL;DR

This study develops new relativistic mean-field models with meson mixing to interpret recent PREX-2 and CREX neutron skin measurements, but finds it challenging to reconcile both results simultaneously.

Contribution

The paper introduces effective interactions with meson mixing in RMF models to connect terrestrial experiments and astrophysical observations of neutron stars.

Findings

Large neutron skin thickness predicted for $^{208}$Pb with $L=70$ MeV.

Difficulty in simultaneously explaining PREX-2 and CREX results.

Meson mixing enhances the model's ability to fit neutron star data.

Abstract

We construct new effective interactions using the relativistic mean-field models with the isoscalar- and isovector-meson mixing, $\sigma^{2}\bm{\delta}^{2}$ and $\omega_{\mu}\omega^{\mu}\bm{\rho}_{\nu}\bm{\rho}^{\nu}$. Taking into account the particle flow data in heavy-ion collisions, the observed mass of PSR J0740$+$6620, and the tidal deformability of a neutron star from binary merger events, GW170817 and GW190814, we study the ground-state properties of finite, closed-shell nuclei, and try to explain the recent results from the PREX-2 and CREX experiments. It is found that the $\sigma$--$\delta$ mixing is very powerful to understand the terrestrial experiments and astrophysical observations of neutron stars self-consistently. We can predict the large neutron skin thickness of $^{208}$Pb, $R_{\rm skin}^{208}=0.243$~fm, using the slope parameter of nuclear symmetry energy, $L=70$~MeV, which is consistent with the PREX-2 result. However, to explain the CREX data, it is preferable to adopt the small value of $L=20$~MeV. It is very difficult to understand the PREX-2 and CREX results simultaneously within relativistic mean-field models.