Toward a global description of nuclear charge radii: Exploring the Fayans energy density functional
Reinhard PG, Nazarewicz W (2017)
Publication Type: Journal article
Publication year: 2017
Journal
Book Volume: 95
Article Number: 064328
Journal Issue: 6
DOI: 10.1103/PhysRevC.95.064328
Abstract
Background: Binding energies and charge radii are fundamental properties of atomic nuclei. When inspecting their particle-number dependence, both quantities exhibit pronounced odd-even staggering. While the odd-even effect in binding energy can be attributed to nucleonic pairing, the origin of staggering in charge radii is less straightforward to ascertain. Purpose: In this work, we study the odd-even effect in binding energies and charge radii, and systematic behavior of differential radii, to identify the underlying components of the effective nuclear interaction. Method: We apply nuclear density functional theory using a family of Fayans and Skyrme energy density functionals fitted to similar data sets but using different optimization protocols. We inspect various correlations between differential charge radii, odd-even staggering in energies and radii, and nuclear matter properties. The Fayans functional is assumed to be in the local FaNDF0 form. Detailed analysis is carried out for medium-mass and heavy semimagic nuclei with a particular focus on the Ca chain. Results: By making the surface and pairing terms dependent on density gradients, the Fayans functional offers the superb simultaneous description of odd-even staggering effects in energies and charge radii. Conversely, when the data on differential radii are added to the pool of fit observables, the coupling constants determining the strengths of the gradient terms of Fayans functional are increased by orders of magnitude. The Skyrme functional optimized in this work with the generalized Fayans pairing term offers results of similar quality. We quantify these findings by performing correlation analysis based on the statistical linear regression technique. The nuclear matter parameters characterizing Fayans and Skyrme functionals optimized to similar data sets are fairly close. Conclusion: The Fayans paring functional, with its generalized density dependence, significantly improves the description of charge radii in odd and even nuclei. Adding differential charge radii to the set of fit observables in the optimization protocol is helpful for both description of radii and for improving the pairing functional. In particular, the Fayans functional FaNDF0 constrained in this way is capable of explaining charge radii in the even-even Ca isotopes. However, in order to obtain good description of differential radii data in both medium-mass and heavy nuclei, an A-dependent scaling of the Fayans pairing functional is still needed. Various extensions of the current model are envisioned that carry out a promise for the global description.
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APA:
Reinhard, P.-G., & Nazarewicz, W. (2017). Toward a global description of nuclear charge radii: Exploring the Fayans energy density functional. Physical Review C - Nuclear Physics, 95(6). https://doi.org/10.1103/PhysRevC.95.064328
MLA:
Reinhard, Paul-Gerhard, and W. Nazarewicz. "Toward a global description of nuclear charge radii: Exploring the Fayans energy density functional." Physical Review C - Nuclear Physics 95.6 (2017).
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