A team of scientists, including Gerald Gabrielse and George Vasmer Leverett of Harvard, John Doyle, Professor of Physics from Yale and David De Mille have set a new benchmark for the near perfect roundness of electrons. Their work has implications for the the Standard Model which is the model of fundamental forces and particles used in physics.

“We know the Standard Model does not encompass everything,” said Yale physicist David DeMille “Like our LHC colleagues, we’re trying to see something in the lab that’s different from what the Standard Model predicts.” The team is hoping to find new particles of matter by testing their effect on the shape of electrons.

On December 19 the group published the most accurate measurement to date of the electrons shape. What they found was that, if the electron is less than perfectly spherical the departure is much smaller than many theories account for. The researchers looked for variations from a spherical shape by checking for a particular deformation in the electron known as an electric dipole moment.

According to LiveScience:

“In their system, the researchers trapped a hafnium fluoride ion in spinning electric fields. Between the hafnium and the fluoride atoms was a huge electric field, which could then trap an electron in place. The spinning electric field rotated slowly enough to stay aligned with the electric dipole moment of the electron, but not so slowly that it allowed the hafnium fluoride ion to escape.

They then pulsed the ion with radio waves and measured the frequencies at which the electron tipped over when it was pointing one way or another. The difference between those two frequencies reveals whether the electron has a dipole moment.”

“You can picture the dipole moment as what would happen if you took a perfect sphere, shaved a thin layer off one hemisphere and laid it on top of the other side,” said David DeMille, who helped establish previous landmark limits in electron deformation. “The thicker the layer, the larger the dipole moment. Now imagine an electron blown up to the size of the earth. Our experiment would have been able to see a layer 10,000 times thinner than a human hair, moved from the southern to the northern hemisphere. But we didn’t see it, and that rules out some theories.”

“It is amazing that some of these predicted supersymmetric particles would squeeze the electron into a kind of egg shape,” said Harvard’s Doyle. “Our experiment is telling us that this just doesn’t happen at our level of sensitivity.”

Gabrielse, also of Harvard, said: “It’s unusual and satisfying that the exquisite precision achieved by our small team in a university lab probes the most fundamental building block of our universe at a sensitivity that complements what is being achieved by thousands at the world’s largest accelerator.”

At a basic level, what this means is that if electrons are less than perfect spheres, as some theories have postulated, the imperfection is too small to measure using current technology. Phys.org has an excellent video, with a graphic demonstration of the experiment.

Source: EurekAlert