Lisa Grossman in Science News:
Electrons are still almost perfectly round, a new measurement shows. A more squished shape could hint at the presence of never-before-seen subatomic particles, so the result stymies the search for new physics.
The electron gets its shape from the way that positive and negative charges are distributed inside the particle. The best theory for how particles behave, called the standard model of particle physics, holds that the electron should keep its rotund figure almost perfectly.
But some theories suggest that an entourage of hypothetical subatomic particles outside the electron could create a slight separation between the positive and negative charges, giving the electron a pear shape. That charge separation is called an electric dipole moment, or EDM. Searching for an electron EDM can reveal if particles that don’t exist in the standard model are hanging around the electron undetected.
More here. [Thanks to Farrukh Azfar.]