Symmetry Energy III: Isovector Skins

Abstract

Isoscalar density is a sum of neutron and proton densities and isovector is a normalized difference. Here, we report on the experimental evidence for the displacement of the isovector and isoscalar surfaces in nuclei, by $\sim$$0.9\text{fm}$ from each other. We analyze data on quasielastic (QE) charge exchange (p,n) reactions, concurrently with proton and neutron elastic scattering data for the same target nuclei, following the concepts of the isoscalar and isovector potentials combined into Lane optical potential. The elastic data largely probe the geometry of the isoscalar potential and the (p,n) data largely probe a relation between the geometries of the isovector and isoscalar potentials. The targets include ${}^{48}$Ca, ${}^{90}$Zr, ${}^{120}$Sn and ${}^{208}$Pb and projectile incident energy values span the range of (10-50)$\text{MeV}$. In our fit to elastic and QE charge-exchange data, we allow the values of isoscalar and isovector radii, diffusivities and overall potential normalizations to float away from those in the popular Koning and Delaroche parametrization. We find that the best-fit isovector radii are consistently larger than isoscalar and the best-fit isovector surfaces are steeper. Upon identifying the displacement of the potential surfaces with the displacement of the surfaces for the densities in the Skyrme-Hartree-Fock calculations, and by supplementing the results with those from analysing excitation energies to isobaric analog states in the past, we arrive at the slope and value of the symmetry energy at normal density of $70<L<101\text{MeV}$ and $33.5<a_a^V<36.4\text{MeV}$, respectively.

58 pages, 21 figures, 3 tables; version accepted for Nuclear Physics A

References in corpus (8)

• Neutron matter at next-to-next-to-next-to-leading order in chiral effective field theory
• Constraints on neutron star radii based on chiral effective field theory interactions
• Constraints on the symmetry energy and on neutron skins from the pygmy resonances in 68Ni and 132Sn
• Symmetry Energy I: Semi-Infinite Matter
• Giant Quadrupole Resonances in 208Pb, the nuclear symmetry energy and the neutron skin thickness
• Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model
• Folding model study of the isobaric analog excitation: isovector density dependence, Lane potential and nuclear symmetry energy
• Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions

Cited by in corpus (25)

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• Determination of the Equation of State from Nuclear Experiments and Neutron Star Observations
• Decoding the Density Dependence of the Nuclear Symmetry Energy
• Bayesian Inference of the Symmetry Energy and the Neutron Skin in ${}^{48}$Ca and ${}^{208}$Pb from CREX and PREX-2
• Constraints on the Symmetry Energy from PREX-II in the Multimessenger Era
• Optical potentials for the rare-isotope beam era
• Symmetry energy constraints from GW170817 and laboratory experiments
• Uncertainty-quantified phenomenological optical potentials for single-nucleon scattering
• Effects of nuclear symmetry energy and equation of state on neutron star properties
• Constraints on high density equation of state from maximum neutron star mass
• EoS constraints from nuclear masses and radii in a meta-modeling approach
• Correlations between charge radii differences of mirror nuclei and stellar observables
• Implications of comprehensive nuclear and astrophysics data on the equations of state of neutron star matter
• Feasibility of dark matter admixed neutron star based on recent observational constraints
• Prediction of (p,n) Charge-Exchange Reactions with Uncertainty Quantification
• Empirical neutron star mass formula based on experimental observables
• Nuclear pasta and symmetry energy in the relativistic point-coupling model
• Constraining nucleon effective masses with flow and stopping observables from the S$\pi$RIT experiment
• Effects of the momentum dependence of nuclear symmetry potential on pion observables in Sn + Sn collisions at 270 MeV/nucleon
• Unraveling the global behavior of equation of state by explicit finite nuclei constraints
• Exploring sensitivity of charge-exchange ($p,n$) reactions to the neutron density distribution
• Transport Model Comparison Studies of Intermediate-Energy Heavy-Ion Collisions
• Investigating the weak charge of ${}^{48}$Ca using a dispersive optical model
• Isospin blocking and its effects in heavy-ion collisions