Symmetry energy constraints from giant resonances: A relativistic mean-field theory overview

Abstract

Abstract. Giant resonances encapsulate the dynamic response of the nuclear ground state to external perturbations. As such, they offer a unique view of the nucleus that is often not accessible otherwise. Although interesting in their own right, giant resonances are also enormously valuable in providing stringent constraints on the equation of state of asymmetric matter. We this view in mind, we focus on two modes of excitation that are essential in reaching this goal: the isoscalar giant monopole resonance (GMR) and the isovector giant dipole resonance (GDR). GMR energies in heavy nuclei are sensitive to the symmetry energy because they probe the incompressibility of neutron-rich matter. Unfortunately, access to the symmetry energy is hindered by the relatively low neutron-proton asymmetry of stable nuclei. Thus, the measurement of GMR energies in exotic nuclei is strongly encouraged. In the case of the GDR, we find the electric dipole polarizability of paramount importance. Indeed, the electric dipole polarizability appears as one of two laboratory observables-with the neutron-skin thickness being the other-that are highly sensitive to the density dependence of the symmetry energy. Finally, we identify the softness of skin and the nature of the pygmy resonance as important unsolved problems in nuclear structure.

Building relativistic mean field models for finite nuclei and neutron stars

“…Note that the answer to the question of Why is Tin so soft?" [50,63,64] continues to elude us to this day [70][71][72][73][74][75][76][77]. By the same token NL3, with a significantly larger value of K than both [59] and charge radii (in fm) [60] for all the nuclei involved in the optimization.…”

Constraining the density slope of nuclear symmetry energy at subsaturation densities using electric dipole polarizability inPb208

“…While many studies on heavy ion collisions and neutron stars have significantly improved our knowledge on the symmetry energy, more and more constraints on the symmetry energy have been obtained in recent years from analyzing the properties of finite nuclei, such as the nuclear binding energy [15][16][17][18][19], the neutron skin thickness [20][21][22], and the resonances and excitations [23][24][25][26][27][28][29][30][31]. Furthermore, it has been realized that the properties of finite nuclei usually provide more precise constraints on E sym (ρ) and L(ρ) at subsaturation densities rather than at saturation density ρ 0 .…”

Influence of the single-particle structure on the nuclear surface and the neutron skin

“…The profile of the neutron density distribution is demanded as an input in the analysis of many scattering experiments. The arrangement of neutrons in nuclei is important for collective nuclear excitations [24,25], such as giant dipole resonance [26,27] and pygmy dipole resonance [28][29][30]. Precise knowledge of the neutron skin thickness (NST), i.e., the difference between the neutron and proton root mean square * warda@kft.umcs.lublin.pl † mariocentelles@ub.edu ‡ xavier@ecm.ub.edu § xavier.roca.maza@mi.infn.it (rms) radii,…”