Large-basis no-core shell-model calculations and their application to 10C→10B Fermi beta decay

We use a 4ℎΩ shell-model calculation with a two-body effective interaction derived microscopically from the Reid93 potential to calculate the isospin-mixing correction for the 10C→10B superallowed Fermi transition. The effective interaction takes into account the coulomb potential as well as the charge dependence of T = 1 partial waves. Our results suggest the isospin-mixing correction δC∼0,1%, which is compatible with previous calculations obtained by other methods. The obtained δC correction is about a factor of four too small to obtain unitarity of the Cabibbo-Kobayashi-Maskawa matrix with the present experimental data. (author)