Constraints on the Symmetry Energy from PREX-II in the Multimessenger Era

Abstract

The neutron skin thickness $\hat{I}”r_{\mathrm{np}}$ of heavy nuclei is essentially determined by the symmetry energy density slope $L(\ddot{I})$ at $\ddot{I}{}_c=0.11{\mathrm{fm}}^{-3}\approx 2/3\ddot{I}{}_0$ ($\ddot{I}{}_0$ is nuclear saturation density), roughly corresponding to the average density of finite nuclei. The PREX collaboration recently reported a model-independent extraction of $\hat{I}”r_{\mathrm{np}}^{208}=0.283\pm 0.071$ fm for the $\hat{I}”r_{\mathrm{np}}$ of ${}^{208}$Pb, suggesting a rather stiff symmetry energy $E_{\mathrm{sym}}(\ddot{I})$ with $L(\ddot{I}{}_c)\ge 52$ MeV. We show that the $E_{\mathrm{sym}}(\ddot{I})$ cannot be too stiff and $L(\ddot{I}{}_c)\le 73$ MeV is necessary to be compatible with (1) the ground-state properties and giant monopole resonances of finite nuclei, (2) the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities from flow data in heavy-ion collisions, (3) the largest neutron star (NS) mass reported so far for PSR J0740+6620, (4) the NS tidal deformability extracted from gravitational wave signal GW170817 and (5) the mass-radius of PSR J0030+045 measured simultaneously by NICER. This allows us to obtain $52\le L(\ddot{I}{}_c)\le 73$ MeV and $0.212\le \hat{I}”r_{\mathrm{np}}^{208}\le 0.271$ fm, and further $E_{\mathrm{sym}}(\ddot{I}{}_0)=34.3\pm 1.7$ MeV, $L(\ddot{I}{}_0)=83.1\pm 24.7$ MeV, and $E_{\mathrm{sym}}(2\ddot{I}{}_0)=62.8\pm 15.9$ MeV. A number of critical implications on nuclear physics and astrophysics are discussed.

6 pages, 4 figures. The published PREX-II result used, results updated and discussions added. Accepted version to appear in Physical Review Research as a Letter