Neutron electric dipole moment in a supersymmetric model with singlet quarks

The neutron electric dipole moment is investigated in a supersymmetric electroweak model admitting SU(2)W singlet and Q = −13, say D-type, quarks. Significant CP violating phases appear in the coupling between the singlet D-type quarks and the ordinary d-type quarks. Then, through the d-D mixing effects on the squark mass terms the gluino one-loop diagrams provide naturally the contributions ∼ 10−26e cm comparable to the current experimental bound on the neutron electric dipole moment. The CP violation in the d-D coupling would also be relevant for the electroweak baryogenesis.