The electron is like a marble

Today comes the ever more precise measurement on the shape of the electron: the electric dipole moment, the researchers ACME Collaboration have observed that the particle has a more spherical shape than that expected from supersymmetry. So, for this time he won the Standard Model.



The electron is more like a ball than an egg: the particle is in fact almost perfectly spherical. This was stated today, by particle physicists at Yale and Harvard ACME Collaboration, who reported the most precise measurement ever obtained on the “shape” of the electron. The study was published in Science Express.

The search team is looking for the same types of particles also in the experiments of the Large Hadron Collider (LHC) at CERN in Geneva, and it does so using methods surprisingly different. In particular, ACME Collaboration is looking for the presence of new particles (and therefore new physics) through the measurement of their possible effects on the shape of the electron, an elementary particle that orbits within each atom.

Some physical theories, such as Supersymmetry (SUSY), introduce the existence of new particles, which have never been observed so far and are not covered by the Standard Model, the theoretical model that describes the past 50 years all the particles and therefore the existing known universe.

In general, the Supersymmetry is a theoretical model that introduces a superpartner for each existing particle, and the two partners of the pair differ in a physical property called spin (if a particle is integer spin his partner is half-integer spin).

“We know that the Standard Model does not encompass everything,” said Yale physicist David DeMille, who along with John Doyle and Gerald Gabriele of Harvard leads the team of ACME. “As a fellow of the LHC, we are trying to observe something in the lab that is different from the predictions of the Standard Model.”



In these models, the new particles such as the electron clouds around, could change its “form”, or more correctly (since the electron is an indivisible particle without internal structure), the symmetry of its interactions with external fields, that is, with other offices. In this way, the electron would acquire an “electric dipole moment” (eEDM), a magnitude that generally quantifies the separation between two charges of opposite sign and, in this case, the asymmetry due to these interactions with other fillers. The researchers measured their electric dipole moment. How? Using electrons inside a polar molecule – with a positive charge on one side and a negative charge on the other – call monoxide thorium. The properties of this molecule amplify the deformation of the electron and reduce the chances of effects that might deceive the presence of a false deformation.

The team was able to get the most accurate measure ever achieved, improving its accuracy by a factor of more than 10: “If you imagine an electron swelled up to the size of the Earth, our experiment would have been able to see the movement from southern hemisphere to the northern hemisphere with a layer 10,000 times thinner than a human hair,”said DeMille. All in a small university lab.

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