Smoother-than-expected electrons could mean rethinking particle physics

Researchers at the Large Hadron Collider have been exploring the limits of physics by smashing particles together, but a team from Yale and Harvard has taken a different approach. The so-called ACME collaboration is taking a closer look at the electron as a way to uncover new exotic particles, but it also has the potential to upend some popular ideas in physics. By taking more precise measurements of electrons, the team has discovered these particles are much more round than they ought to be — so perfectly round that they could change our understanding of particle physics.

The Standard Model is the theory describing the interaction of forces affecting subparticles, like electrons and quarks. Physicists have long relied on the Standard Model to make experimental predictions, while at the same time knowing that it isn’t perfect. The Standard Model is simply the best answer we have right now, and it’s accepted to be close enough to reality to be a useful tool.

Many of the truly interesting things going on at CERN and other research facilities have to do with finding out where the Standard Model breaks down. Going beyond the Standard Model, physicists have proposed various explanations for these gaps in our knowledge. Supersymmetry is one such idea that holds each particle has a superpartner with the same mass and internal quantum numbers, but opposite spin. It is these particles the ACME project was looking for by observing electrons.

The team has been measuring electrons for a type of deformation called the electric dipole moment. If an electron were to interact with many particles predicted by supersymmetry it could change shape quite dramatically, possibly making it more egg shaped than round. However, the ACME researchers found that even very slight deformations were not present — electrons are consistently spherical.

So what does that mean? Some of the theorized particles would have caused massive deformation of electrons when observed under experimental conditions. Having not seen anything of the sort, that could mean the particles simply don’t exist and our understanding of the Standard Model is still incomplete, even with the addition of supersymmetry. Then there is the possibility that the experiment itself was flawed.

On that last count, the team seems confident its observations are correct. The electrons used in the experiment were within the polar molecule thorium monoxide, which amplifies the electric dipole moment. According to one of the lead researchers, if an electron were the size of Earth, this experiment would be able to detect a deformation 10,000 times thinner than a human hair. With that in mind, the smooth curve of the electron might mean the quantum soup of subparticles is much stranger than we thought. It could be a big revelation and we didn’t even need any gigantic supercolliders to figure it out.