The charge radii of calcium isotopes within relativistic density functional theory: nucleon's finite-size and quadrupole shape fluctuation effects

TL;DR

This study uses relativistic density functional theory to explain the long-standing anomaly in calcium isotope charge radii by including nucleon finite-size and shape fluctuation effects, achieving accurate reproduction of experimental data.

Contribution

It provides the first self-consistent nuclear theory solution to the calcium charge radii anomaly without local parameter adjustments, highlighting the importance of nucleon structure and shape fluctuations.

Findings

Reproduces the similar charge radii of $^{40}$Ca and $^{48}$Ca.

Explains the inverted parabolic behavior of charge radii between these isotopes.

Highlights the role of shape fluctuations in isotonic charge radius shifts.

Abstract

The anomaly in the charge radii of Ca isotopes has been puzzling for nuclear theory for decades. We present the first self-consistent solution to this puzzle within the density functional theory without resorting to local parameter adjustment. By taking into account both the intrinsic electromagnetic structure of nucleons and the zero-point motions of nuclear shape, which have been often neglected in previous studies, the similar charge radii of $^{40}$Ca and $^{48}$Ca as well as an inverted parabolic behavior between them are reproduced. It is found that these effects also play crucial roles in the description of the isotonic shift between the charge radii of Sn and Cd isotopes.