Author: Lisa Grossman / Source: 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.
Now, the Advanced Cold Molecule Electron Electric Dipole Moment, or ACME, search, based at Harvard University, has probed the electron’s EDM with the most precision ever — and still found no sign of smooshing, the team reports online October 17 in Nature.
The finding improves the team’s last best measurement (SN Online: 12/19/13) by a factor of 10 to find an EDM of 10-29 electron charge centimeters. That’s as round as if the electron were a sphere the size of the Earth,…
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