Radial and orbital decomposition of charge radii of Ca nuclei:Comparative study of Skyrme and Fayans functionals

TL;DR

This study compares the charge radii of calcium isotopes using Fayans and Skyrme density functionals, decomposing contributions to understand their different predictions and emphasizing the importance of modeling both neutron-rich and neutron-deficient regions accurately.

Contribution

It provides a detailed decomposition of charge radii into radial and orbital parts within density functional theory, highlighting differences between Fayans and Skyrme functionals in calcium isotopes.

Findings

Fayans functional captures the N-dependence of charge radii in 20≤N≤28.

Fayans functional overestimates charge radii for N<20, contradicting experimental data.

Decomposition reveals the physical origin of radius variations in different neutron number regions.

Abstract

We investigate the charge and point-proton radii of the Ca nuclei in detail in the density functional theory framework. As the Fayans energy density functional provides characteristic $N$-dependence, successfully describing the parabolic behavior of the differential charge radii in $20\leq N\leq 28$, we pose our particular focus on its physics origin, by decomposing them into the radial and orbital contributions. The results are compared with those from the Skyrme plus usual pairing functional, which is taken as a representative of the functionals having normal pairing channels. We point out that, because the enhancement of the differential charge radii in $N<20$ with the Fayans functional, which is contradictory with the data, has the origin parallel to the parabolic behavior in $20\leq N\leq 28$, it is significant to describe both $N$ regions simultaneously.