Abstract

Our current knowledge of the Equation of State of asymmetric nuclear matter around saturation density and of the energy of the Isobaric Analog State in a heavy nucleus such as 208Pb seem to be in contradiction. In Ref. [1], the problem has been highlighted and a solution has been proposed. In the present contribution, we overview the aforementioned work by giving some new details not previously published.

Highlights

  • One of the most outstanding problems in nuclear physics is the accurate determination of the nuclear equation of state (EoS) [2, 3]

  • The nuclear symmetry energy is one of the fundamental ingredients to describe the EoS when dealing with isospin asymmetric matter [4, 5] and its determination may entail profound consequences in our understanding of heavy-ion reactions [6], neutron stars [7], or of the Standard Model via atomic parity violation [8]

  • If β is the local neutron-proton asymmetry, β ≡/ρ, the energy per particle in matter having neutron-proton imbalance is a function. Such function can be expanded in even powers of β owing to isospin symmetry

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Summary

Introduction

One of the most outstanding problems in nuclear physics is the accurate determination of the nuclear equation of state (EoS) [2, 3]. The Isobaric Analog State (IAS) is one of the well established properties of nuclei that is measured accurately, and is only sensitive to the isospin symmetry breaking (ISB) in the nuclear medium due to Coulomb interaction and, to a lesser extent, the other effects discussed below. The experimental IAS energy [31] is shown (horizontal dashed line) in the figure, and a simple extrapolation implies ∆Rnp = 0.07(2) fm This value is incompatible with previous studies [9, 11, 32]. Recent experimental constraints from polarized proton elastic scattering [29], parity violating elastic electron scattering [19], and electric dipole polarizability [30], are indicated in the bottom part of Fig. 1 To solve this puzzle, we have reconsidered in Ref. Note that none of the new terms impacts to the proton-neutron RPA residual force

Electromagnetic spin-orbit
Coulomb exchange
Vacuum polarization correction
Finite size effects
Charge symmetry breaking and charge independence breaking potentials
Results
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