Electron electric dipole moment

The electron electric dipole moment (EDM) "d"e is an intrinsic property of an electron such that the potential energy is linearly related to the strength of the electric field: 
The electron's EDM must be collinear with the direction of the electron's magnetic moment (spin). Within the Standard Model of elementary particle physics, such a dipole is predicted to be non-zero but very small, at most , where "e" stands for the elementary charge. The discovery of a substantially larger electron electric dipole moment would imply a violation of both parity invariance and time reversal invariance.
Implications for Standard Model and extensions.
In the Standard Model, the electron EDM arises from the CP-violating components of the CKM matrix. The moment is very small because the CP violation involves quarks, not electrons directly, so it can only arise by quantum processes where virtual quarks are created, interact with the electron, and then are annihilated.
If neutrinos are Majorana particles, a larger EDM (around ) is possible in the standard model
Many extensions to the Standard Model have been proposed in the past two decades. These extensions generally predict larger values for the electron EDM. For instance, the various technicolor models predict "d"e that ranges from 10−27 to 10−29 "e"⋅cm. Some supersymmetric models predict that but some other parameter choices or other supersymmetric models lead to smaller predicted values. The present experimental limit therefore eliminates some of these technicolor/supersymmetric theories, but not all. Further improvements, or a positive result, would place further limits on which theory takes precedence.
Formal definition of the electron EDM.
As the electron has a net charge, the definition of its electric dipole moment is ambiguous in that 
depends on the point formula_3 about which the moment of the charge distribution formula_4 is taken. If we were to choose formula_3 to be the center of charge, then formula_6 would be identically zero.
A more interesting choice would be to take formula_3 as the electron's center of mass evaluated in the frame in which the electron is at rest.
Classical notions such as the center of charge and mass are, however, hard to make precise for a quantum elementary particle. In practice the definition used by experimentalists comes from the form factors formula_8 appearing in the matrix element 
of the electromagnetic current operator between two on-shell states with Lorentz invariant phase space normalization in which 
Here formula_11 and formula_12 are 4-spinor solutions of the Dirac equation normalized so that formula_13, and formula_14 is the momentum transfer from the current to the electron. 
The formula_15 form factor formula_16 is the electron's charge, formula_17 is its static magnetic dipole moment, and formula_18 provides the formal definition of the electron's electric dipole moment.
The remaining form factor formula_19 would, if nonzero, be the anapole moment.
Experimental measurements of the electron EDM.
To date, no experiment has found a non-zero electron EDM. As of 2020 the Particle Data Group publishes its value as . Here is a list of some electron EDM experiments after 2000 with published results:
Future proposed experiments.
Besides the above groups, electron EDM experiments are being pursued or proposed by the following groups: