Impact of pion tensor force on alpha clustering in $^{20}$Ne

TL;DR

This study investigates how pion tensor forces influence alpha clustering in $^{20}$Ne, revealing their significant role in nuclear structure and decay properties through advanced relativistic models.

Contribution

It demonstrates the impact of pion-exchanged tensor forces on nuclear deformation, single-particle levels, and alpha clustering in $^{20}$Ne, providing new insights into nuclear force effects.

Findings

Tensor force enlarges level branches in deformed prolate states.

Tensor interaction reduces excitation energy closer to alpha decay threshold.

Pion tensor force significantly alters nucleonic localization and clustering configurations.

Abstract

The nuclear clustering, as a quantum phase transition phenomenon governed by strong interactions, exhibits characteristics that are highly sensitive to the specific features of nuclear forces. Here, we examine how nuclear deformation and tensor forces influence $\alpha$-cluster formation in light nuclei. The axially deformed relativistic Hartree-Fock-Bogoliubov model is utilized to investigate the clustering structure of the $^{20}$Ne nucleus, at both the ground state and the excited state with a superdeformed prolate. The nuclear binding energies and the canonical single particle levels are obtained at different quadruple deformation, and the role of tensor force embedded in the Fock diagram of $\pi$-pseudovector ($\pi$-PV) coupling is revealed. It is shown that the level branches from the degenerated spherical orbits at the deformed prolate case are enlarged due to the extra contribution from pion-exchanged tensor force. Correspondingly, the excitation energy in this superdeformed prolate state is reduced due to the noncentral tensor interaction, leading to a predicted value which is much closer to the referred threshold for the $2\alpha$ decay mode of $^{20}$Ne. Possible $\alpha$-clustering configurations in $^{20}$Ne are then characterized by examining the nucleonic localization function. Although the contribution to the ground state is relatively small, the density profile and nucleonic localization are significantly changed by the pion tensor force for the superdeformed prolate excited state, as further evidenced by characterising the level mixing in the spherical basis components. The results reveal the extra role of the tensor force, correlated to the evolved single-particle levels with nuclear deformation, in the formation and stability of nuclear clustering.