Science reports:

A measurement of the humble electron has dimmed particle physicists’ long-held hopes of discovering exotic new particles. The finding, reported today in Science, confirms to greater precision than ever before that the distribution of electric charge in the electron is essentially round. The result implies that any new fundamental particles lurking undiscovered in the vacuum might be too massive for even the world’s biggest atom smasher, the Large Hadron Collider (LHC), to produce.

“It’s a fantastic result,” says John Doyle, a physicist at Harvard University and co-leader of a competing experiment that set the previous limit on a charge asymmetry known as the electric dipole moment. “We both found essentially the same result—theirs is a factor of 2 better—and because the techniques are so different, it firmly establishes that measurement.” The result may also make it harder for theorists to explain how the infant universe generated more matter than antimatter, Doyle says.

To explain how that imbalance evolved—and, thus, why anything at all exists—physicists posit that some of the rules governing the interactions of fundamental particles must look different if run forward or backward in time, which would imply matter and antimatter behave slightly differently. In fact, the interactions of quarks, the building blocks of protons and neutrons, do violate that symmetry, but not by enough to have generated the cosmic matter-antimatter imbalance. [Continue reading…]