Abstract
We analyze and propose a solution to the apparent inconsistency between our current knowledge of the equation of state of asymmetric nuclear matter, the energy of the isobaric analog state (IAS) in a heavy nucleus such as ^{208}Pb, and the isospin symmetry breaking forces in the nuclear medium. This is achieved by performing state-of-the-art Hartree-Fock plus random phase approximation calculations of the IAS that include all isospin symmetry breaking contributions. To this aim, we propose a new effective interaction that is successful in reproducing the IAS excitation energy without compromising other properties of finite nuclei.
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
Summary
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
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