  The CKM matrix and its unitarity is analyzed by disentangling experimental
information obtained from three different particle systems of neutrons, mesons,
and nuclei. New physics beyond the Standard Model is supported under the new
analysis. In particular, the newly proposed mirror-matter model [Phys. Lett. B
797, 134921 (2019)] can provide the missing physics and naturally extend the
CKM matrix. Laboratory experiments with current technology for measuring
neutron, meson, and nuclear decays under various scenarios are proposed. Such
measurements can provide stringent tests of the new model and the extended CKM
matrix.
