Non-unitarity of CKM matrix from vector singlet quark mixing and neutron electric dipole moment

In the standard model (SM) the lowest order contribution to the quark elect ric dipole moment (EDM) occurs at the three loop level. We show that the no n-unitarity of the CKM matrix in models with an extended quark sector typic ally gives rise to a quark EDM at the two loop level which has no GIM-like suppression factors except the external quark mass. The induced neutron EDM is of order 10(-29) e cm and can be well within the reach of the next gene ration of experiments if it is further enhanced by long distance physics as happens in the SM. (C) 2001 Published by Elsevier Science B.V.