Mirror symmetry breaking in He isotopes and their mirror nuclei

TL;DR

This study investigates mirror symmetry breaking in helium isotopes and their mirror nuclei using a cluster model, revealing how Coulomb interactions influence nuclear radii and configurations, especially in excited states.

Contribution

The paper introduces a detailed cluster model analysis of mirror symmetry breaking in helium isotopes, highlighting the role of Coulomb effects and valence nucleon configurations in nuclear radii.

Findings

Ground state radius of 8C is larger than 8He due to Coulomb repulsion.

In 0+2 states, 8C radius is smaller than 8He because of Coulomb barrier effects.

Large spatial extension of valence nucleons observed in excited states of 8He and 8C.

Abstract

We study the mirror symmetry breaking of $^6$He-$^6$Be and $^8$He-$^8$C using the $^4$He + $X$N ($X$=2, 4) cluster model. The many-body resonances are treated for the correct boundary condition using the complex scaling method. We find that the ground state radius of $^8$C is larger than that of $^8$He due to the Coulomb repulsion in $^8$C. On the other hand, the $0^+_2$ resonances of the two nuclei exhibit the inverse relation; the $^8$C radius is smaller than the $^8$He radius. This is due to the Coulomb barrier of the valence protons around the $^4$He cluster core in $^8$C, which breaks the mirror symmetry of the radius in the two nuclei. A similar variation in the radius is obtained in the mirror nuclei, $^6$He and $^6$Be. A very large spatial extension of valence nucleons is observed in the $0^+_2$ states of $^8$He and $^8$C. This property is related to the dominance of the $(p_{3/2})^2(p_{1/2})^2$ configuration for four valence nucleons, which is understood from the reduction in the strength of the couplings to other configurations by involving the spatially extended components of valence nucleons.