The pygmy dipole strength, the neutron radius of ${}^{208}$Pb and the symmetry energy

Abstract

The accurate characterization of the nuclear symmetry energy and its density dependence is one of the outstanding open problems in nuclear physics. A promising nuclear observable in order to constrain the density dependence of the symmetry energy at saturation is the neutron skin thickness of medium and heavy nuclei. Recently, a low-energy peak in the isovector dipole response of neutron-rich nuclei has been discovered that may be correlated with the neutron skin thickness. The existence of this correlation is currently under debate due to our limited experimental knowledge on the microscopic structure of such a peak. We present a detailed analysis of Skyrme Hartree-Fock (HF) plus random phase approximation (RPA) predictions for the dipole response in several neutron-rich nuclei and try to elucidate whether models of common use in nuclear physics confirm or dismiss its possible connection with the neutron skin thickness. Finally, we briefly present theoretical results for parity violating electron scattering on ${}^{208}$Pb at the conditions of the PREx experiment and discuss the implications for the neutron skin thickness of ${}^{208}$Pb and the slope of the symmetry energy.

Contribution to the 2nd Iberian Nuclear Astrophysics Meeting on Compact Stars proceedings

References in corpus (10)

• Nuclear symmetry energy probed by neutron skin thickness of nuclei
• Exotic modes of excitation in atomic nuclei far from stability
• Neutron skin of 208Pb, nuclear symmetry energy, and the parity radius experiment
• Constraints on the symmetry energy and on neutron skins from the pygmy resonances in 68Ni and 132Sn
• The Giant Dipole Resonance as a quantitative constraint on the symmetry energy
• Neutron skin thickness in droplet model with surface width dependence: indications of softness of the nuclear symmetry energy
• Neutron density distributions from antiprotonic 208Pb and 209Bi atoms
• Impact of the symmetry energy on the outer crust of non-accreting neutron stars
• Origin of the neutron skin thickness of 208Pb in nuclear mean-field models
• Theoretical study of elastic electron scattering off stable and exotic nuclei