Enhancement of the CP-odd effect in the nuclear electric dipole moment of $^6$Li

TL;DR

This paper calculates the electric dipole moment of $^6$Li using a three-body cluster model, revealing enhanced sensitivity to CP-odd nuclear forces, and compares results with ab initio methods for light nuclei.

Contribution

First calculation of $^6$Li EDM with a cluster model showing increased sensitivity to CP-odd forces, and comparison with ab initio results for light nuclei.

Findings

$^6$Li EDM is twice as sensitive to isovector pion exchange CP-odd force as the deuteron.

Good agreement between ab initio and previous calculations for deuteron, $^3$H, and $^3$He EDMs.

The study discusses implications for physics beyond the Standard Model.

Abstract

We calculate for the first time the electric dipole moment (EDM) of the $^6$Li nucleus within the alpha + p + n three-body cluster model using the Gaussian expansion method, assuming the one meson exchange P, CP-odd nuclear forces. It is found that the EDM of the $^6$Li is 2 times more sensitive on the isovector pion exchange P, CP-odd nuclear force than the deuteron EDM, due to the CP-odd interaction between the nucleons and the alpha cluster. The $^9$Be EDM is also calculated in the same framework as an alpha + alpha + n three-body system. We also test the ab initio calculation of the EDM of the deuteron, $^3$H and $^3$He nuclei using the realistic Argonne $v18$ nuclear force. In the ab initio calculations, good agreements with previous studies are obtained. We finally discuss the prospects for the new physics beyond the standard model.