Detailed examination of astrophysical constraints on the symmetry energy and the neutron skin of ²⁰⁸Pb with minimal modeling assumptions

Journal Article · Wed Dec 15 00:00:00 EST 2021 · Physical Review. C

DOI:https://doi.org/10.1103/physrevc.104.065804· OSTI ID:1869603

Essick, Reed  ^[1]; Landry, Philippe ^[2]; Schwenk, Achim  ^[3]; Tews, Ingo  ^[4]

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1. Perimeter Institute for Theoretical Physics, Waterloo (Canada); Univ. of Chicago, IL (United States)
2. California State Univ., Fullerton, CA (United States)
3. Technische Univ. Darmstadt (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt (Germany); Max-Planck-Institut für Kernphysik, Saupfercheckweg, Heidelberg (Germany)
4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

We report the symmetry energy and its density dependence are pivotal for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of 0.283 ± 0.071 fm for the neutron-skin thickness of ²⁰⁸Pb, $$R^{^{208}Pb}_{skin}$$, implying a symmetry-energy slope parameter L of 106 ± 37 MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy S₀, L, and $$R^{^{208}Pb}_{skin}$$ directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER favor smaller values of the neutron skin and L, as well as negative symmetry incompressibilities. Combining astrophysical data with chiral effective field theory (χEFT) and PREX-II constraints yields S₀ = 33.0$$^{+2.0}_{-1.8}$$ MeV, L = 53$$^{+14}_{-15}$$ MeV, and $$R^{^{208}Pb}_{skin}$$ = 0.17 $$^{+0.04}_{-0.04}$$ fm. We also examine the consistency of several individual χEFT calculations with astrophysical observations and terrestrial experiments. We find that there is only mild tension between χ EFT, astrophysical data, and PREX-II's $$R^{^{208}Pb}_{skin}$$ measurement (p value = 12.3%) and that there is excellent agreement between χEFT, astrophysical data, and other nuclear experiments.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); National Energy Research Scientific Computing Center (NERSC); National Science Foundation (NSF); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR); USDOE Office of Science (SC), Nuclear Physics (NP); German Research Foundation (DFG); Kavli Foundation; Canadian Institute for Advanced Research (CIFAR); Science and Economic Development Canada
• Grant/Contract Number: 89233218CNA000001; AC02-05CH11231; PHY-0823459; PHY-0757058; OISE-1927130; AC52-06NA25396; PHY-1836734
• OSTI ID: 1869603
• Report Number(s): LA-UR-21-21363; TRN: US2306416
• Journal Information: Physical Review. C, Vol. 104, Issue 6; ISSN 2469-9985
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
gravitational waves
nuclear astrophysics
nuclear matter in neutron stars
nucleon distribution
symmetry energy
x-ray astronomy
Bayesian methods