Complete Electric Dipole Response in ¹²⁰Sn and ²⁰⁸Pb and Implications for Neutron Skin and Symmetry Energy

Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany

^a e-mail: vnc@ikp.tu-darmstadt.de

Published online: 28 May 2015

Abstract

Polarized proton scattering at energies of a few 100 MeV and extreme forward angles including 0° has been established as a new tool to extract the complete E1 response in nuclei up to excitation energies of about 20 MeV. A case study of ²⁰⁸Pb demonstrates excellent agreement with other electromagnetic probes. From the information on the B(E1) strength one can derive the electric dipole dipole polarizability, which is strongly correlated to the neutron skin and to parameters of the symmetry energy. Recently, we have extracted the polarizability of ¹²⁰Sn with a comparable precision. The combination of both results further constrains the symmetry energy parameters and presents a challenge for mean-field models, since the relativistic and many Skyrme parameterizations cannot reproduce both experimental results simultaneously.