A way forward in the study of the symmetry energy: experiment, theory, and observation

Abstract

The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy ion collisions, and astronomical observations. We then present a roadmap to make progress in areas of relevance to the symmetry energy that promotes collaboration between the astrophysics and the nuclear physics communities.

Effects of the symmetry energy on the isovector properties of neutron-rich nuclei within a Thomas-Fermi approach

“…It is remarkable that the allowed pairs of L and J consistent with our approach (see the colored lines in Fig. 5) lie at the intersection of the bands originating from other approaches [10]. Fig.…”

“…5 we compare the allowed pairs of L and J constrained from heavy-ion collisions and nuclear structure observable [10] with those found in the present approach. Actually the present results lie inside the intersection area suggested by the measurements of the dipole polarizability a D as well as those found by heavy-ion collisions experiments.…”

“…In any case, additional experimental work is necessary to constrain the neutron skin [10]. In particular the upcoming Lead Radius Experiment II (PREX-II) promises to determine the neutron-skin thickness of 208 Pb with a ±0.06 fm accuracy while the Calcium Radius Experiment (CREX) will provide a high precision measurement for the neutron radius of 48 Ca with accuracy ±0.02 fm [10]. The above measurements will be a very good test for all the theoretical models including the present variational approach.…”

“…Actually there is a variety of neutron star properties which are sensitive to SE, that is the maximum mass value and the corresponding radius, the onset of the direct Urca process, the crust-core transition density and pressure e.t.c. [2,9] Recently, there is an extended theoretical [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,57,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,…”

Neutron skin thickness from the measured electric dipole polarizability inNi68,Sn120, andRoca-Maza1, Viñas2, Centelles3 et al. 2015Phys. Rev. C238322563View full textAdd to dashboardCite

“…These estimates are consistent with other predictions of the neutron skin thickness, J, and L extracted from various experiments that include heavy-ion collisions, giant resonances, antiprotonic atoms, hadronic probes, polarized electron scattering, as well as astrophysical observations; see, e.g., Refs. [53,54,57,59,61]. Finally, the correlation between the electric dipole polarizabilities in 68 Ni, 120 Sn, and 208 Pb shows that almost all the EDFs that reproduce the measured polarizability in 208 Pb also reproduce the measured polarizabilities in 68 Ni and 120 Sn.…”