If you've ever looked at a model of the atom, you'd probably guess that electrons are spherical. But these elementary particles are actually slightly egg-shaped...and proving that could mean trouble for one particular model of subatomic physics.
Now, make no mistake - even if you made an electron big enough to be seen with the naked eye, it would still look almost perfectly spherical. These are very small distortions we're talking about, and because electrons themselves are so very, very small, it's an open question whether we actually have the technology needed to detect these distortions. According to the Standard Model, the egg-shaped distortion is so small that it's only noticeable for every one part in 10^28.
There's another model of subatomic physics that says the distortion should be much more noticeable, anywhere between one part in 10^14 and 10^19. This is the model that incorporates supersymmetry, which posits that all the elementary particles we know have a superpartner that is considerably more massive and differs by half a spin. For more on these sparticles, you can check out our primer on undiscovered particles here.
But it's starting to look like these sparticles will remain forever undiscovered. An earlier experiment offered some evidence against supersymmetry, and now research by Jony Hudson and colleagues at Imperial College London has made things even more uncomfortable for this model.
In an effort to detect the egg-like distortions of the electron, the researchers designed an experiment that would be able to detect any distortions up to one part in 10^18, as New Scientist explains:
They used ultracold molecules of ytterbium fluoride in which the centres of positive and negative charge differ, creating a dipole. The shape of this dipole reflects the asymmetry of the electron shape, and the team measured this by placing the molecules in an electric and a magnetic field and observing how they spin as the fields are changed. Variations in the rate of spin reveal any asymmetry.
The experiment was unable to turn up any evidence that the electrons were egg-shaped, which means that the distortion doesn't kick in until somewhere past one part in 10^18. That removes most of the possible range of distortion according to supersymmetry. Indeed, improving the experiment by just one order of magnitude could be enough to rule out supersymmetry completely, meaning that entire model would crack like...wait, I had something for this.