Electric Dipole Moment of the Neutron: Expected Order of Magnitude

Abstract

Sideways dispersion relations yield a theoretically well-defensible "lower limit" on the expected order of magnitude of the neutron electric dipole moment. If $T$ violation is due to the weak interactions, then ${10}^{-24\mathrm{}}$ e cm appears as a reasonable expectation, and ${10}^{-23\mathrm{}}$ e cm the most one can hope for. If $T$ violation is due to the electromagnetic interactions of hadrons, we still cannot safely expect more than ${10}^{-23\mathrm{}}$ e cm, although optimistic guesses can easily yield 6×${10}^{-22\mathrm{}}$ e cm or more.