What is Electron ?

Thus, naively, the EDM would quantify the “dumbbellness” of a macroscopic object.

The story of EDM, however, is very different in the quantum world. There the vacuum around an electron is not empty and still.

Rather it is populated by various subatomic particles zapping into virtual existence for short periods of time.

These virtual particles form a “cloud” around an electron. If we shine light onto the electron

some of the light could bounce off the virtual particles in the cloud instead of the electron itself.

This would change the numerical values of the electron’s charge and magnetic and electric dipole moments.

Performing very accurate measurements of those quantum properties would tell us how these elusive virtual particles behave when they interact with the electron and if they alter the electron’s EDM

Most intriguing, among those virtual particles there could be new, unknown species of particles that we have not yet encountered.

To see their effect on the electron’s electric dipole moment, we need to compare the result of the measurement to theoretical predictions of the size of the EDM calculated in the currently accepted theory of the Universe, the Standard Model.

Yet, it is unable to address many of the most fundamental questions, such as why matter dominates over antimatter throughout the universe.

The Standard Model makes a prediction for the electron’s EDM too: it requires it to be so small that ACME would have had no chance of measuring it.

But what would have happened if ACME actually detected a non-zero value for the electric dipole moment of the electron?

Theoretical models have been proposed that fix shortcomings of the Standard Model, predicting the existence of new heavy particles.

These models may fill in the gaps in our understanding of the universe.

To verify such models we need to prove the existence of those new heavy particles.

This could be done through large experiments, such as those at the international Large Hadron Collider (LHC) by directly producing new particles in high-energy collisions.

Alternatively, we could see how those new particles alter the charge distribution in the “cloud” and their effect on electron’s EDM.

Thus, unambiguous observation of electron’s dipole moment in ACME experiment would prove that new particles are in fact present. That was the goal of the ACME experiment.

This is the reason why a recent article in Nature about the electron caught my attention.

An electron is a negatively charged subatomic particle. It can be either free (not attached to any atom), or bound to the nucleus of an atom. Electrons in atoms exist in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron.

Theorists like myself use the results of the measurements of electron’s EDM – along with other measurements of properties of other elementary particles – to help to identify the new particles and make predictions of how they can be better studied.

In electrical conductors, current flow results from the movement of electrons from atom to atom individually, and from negative to positive electric poles in general. In semiconductor materials, current also occurs as a movement of electrons.

This is done to clarify the role of such particles in our current understanding of the universe.

What should be done to measure the electric dipole moment? We need to find a source of very strong electric field to test an electron’s reaction.

But in some cases, it is more illustrative to envision the current as a movement of electron deficiencies from atom to atom. An electron-deficient atom in a semiconductor is called a hole. Holes "move" from positive to negative electric poles in general.