Imprints of $\alpha$ clustering in the density profiles of $^{12}$C and $^{16}$O

TL;DR

This paper investigates alpha clustering in the ground states of $^{12}$C and $^{16}$O using intrinsic Slater determinants, revealing how cluster and shell structures compete and manifest in density profiles and scattering data.

Contribution

It introduces a unified approach using intrinsic Slater determinants to distinguish and visualize alpha-cluster and shell-model structures in nuclei.

Findings

Enhanced elastic scattering cross sections indicate developed cluster structures.

Density profiles reveal internal clustering at higher momentum transfers.

Trial states successfully reproduce experimental charge radii.

Abstract

The $^{4}$He nucleus is a well bound and highly correlated four-nucleon system that is also found in form of $\alpha$-clusters as substructure in nuclear many-body systems. The standard single-particle shell model cannot represent these four-body correlations. It is highly desirable to find a simple way to identify and distinguish these fundamental structures without large-scale computations. In this paper, we investigate with intrinsic Slater determinants as trial states in how far these two competing pictures prevail in the ground states of $^{12}$C and $^{16}$O. The trial states can describe both the $j$-$j$ coupling shell-model and $\alpha$-cluster configurations in a unified way. One-body density distributions of the trial states are calculated and compared to elastic scattering cross section data. The parameters of the trial state are chosen to reproduce the experimental charge radii. A well developed cluster structure is characterized by an enhancement of the differential elastic scattering cross sections, as well as the elastic charge form factors around the first peak positions. The density profiles of the internal regions can also be probed at higher momentum transfer regions beyond the second minimum. With these trial states one can visualize the competition between cluster and shell structure in an intuitive and simple way.