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 × 10⁻³¹e.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| > 10⁻²⁵e.cm,

(iv) in a class of left-right symmetric models D_n is of the order of 10^−26±1e.cm,

(v) in supersymmetric models, D_n is of order 10⁻²²ϕ 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 × 10⁻²⁵e.cm with 90% confidence.