Determination of the Upper Limit to the Electric Dipole Moment of the Electron at High Momentum Transfer

A new limit on the electron's electric dipole moment at high momentum transfer has been determined by scattering 100-MeV electrons at 180° from ${\mathrm{C}}^{12}$ nuclei. A full discussion of the theory involved and the experimental corrections due to multiple scattering, etc. is given. Assuming that the electron possesses no spurious magnetic moment, apart from the well-established Dirac and anomalous moments, its electric dipole moment is $\lesssim 2.3\times {10}^{-16\mathrm{}}e$ cm at a momentum transfer of 1.0 ${\mathrm{fermi}}^{-1\mathrm{}}$. (A more detailed interpretation of the experiment is discussed in the conclusion.) The result is consistent with time-reversal invariance in quantum electrodynamics.