Nuclear electric dipole moment in the cluster model with a triton: ${}^7$Li and ${}^{11}$B

Abstract

We calculate the electric dipole moment (EDM) of the nuclei ${}^7$Li and ${}^{11}$B in the cluster model with $\alpha$ (${}^4$He) and triton (${}^3$H) clusters as degrees of freedom. The ${}^7$Li and ${}^{11}$B nuclei are treated in the two- and three-body problem, respectively, using the Gaussian expansion method, assuming the one-meson exchange P, CP-odd nuclear forces. We find that ${}^7$Li and ${}^{11}$B have larger sensitivity to the CP violation than the deuteron. It is also suggested that the EDMs of ${}^7$Li and ${}^{11}$B, together with those of ${}^6$Li, ${}^9$Be and the $1/2_1^{+}$ excited state of ${}^{13}$C, obey an approximate counting rule accounting for the EDM of the cluster and the $\alpha -N$ polarization. We show their sensitivity on the hadronic level CP violation in terms of the chiral effective field theory, and discuss their role in probing new physics beyond the standard model.

Comments: 12 pages, 2 figures