The Neutron Electric Dipole Moment

We have made a systematic study of the electric dipole moment (EDM) of neutron D n in various models of CP violation. We find that (i) in the standard KM model with 3 families, the neutron EDM is in the range 1.4 × 10 −33 ≤ |D n | ≤ 1.6 × 10 −31 e.cm , (ii) the two Higgs doublet model has approximately the same value of D n as the standard model, (iii) D n in the Weinberg model is predicted to satisfy |D n | > 10 −25 e.cm , (iv) in a class of left-right symmetric models D n is of the order of 10 −26±1 e.cm , (v) in supersymmetric models, D n is of order 10 −22 ϕ e.cm with ϕ being the possible phase difference of gluino mass and the gluino-quark-squark mixing matrix, (vi)the strong CP parameter θ is found to be θ < 10 −9 , using the present experimental limit that |D n | < 2.6 × 10 −25 e.cm with 90% confidence.