Mirror symmetry breaking in He isotopes and their mirror nuclei

We study the mirror symmetry breaking of He-6-Be-6 and He-8-C-8 using the He-4 + XN(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 C-8 is larger than that of He-8 due to the Coulomb repulsion in C-8. On the other hand, the 0(2)(+) resonances of the two nuclei exhibit the inverse relation; the C-8 radius is smaller than the He-8 radius. This is due to the Coulomb barrier of the valence protons around the He-4 cluster core in C-8, which breaks the mirror symmetry of the radius in the two nuclei. A similar variation in the radius is obtained in the mirror nuclei, He-6 and Be-6. A very large spatial extension of valence nucleons is observed in the 0(2)(+) states of He-8 and C-8. 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.