Improved Limit on the Electric Dipole Moment of the Electron

October 17, 2018

In this artist's representation, an electron orbits an atom's nucleus, spinning about its axis as a cloud of other subatomic particles are constantly emitted and reabsorbed. Several hypotheses predict particles, as yet undetected, would cause the cloud to appear slightly pear-shaped. ACME researchers peered at the shape with unprecedented, extreme precision. To the limits of their experiment, they saw a perfectly round sphere, implying that certain types of new particles -- if they exist at all -- have properties different from those theorists expected. Credit: Nicolle R. Fuller, National Science Foundation

In a new study, researchers at Northwestern, Harvard and Yale universities examined the shape of an electron's charge with unprecedented precision to confirm that it is perfectly spherical. A slightly squashed charge could have indicated unknown, hard-to-detect heavy particles in the electron's presence, a discovery that could have upended the global physics community.

"If we had discovered that the shape wasn't round, that would be the biggest headline in physics for the past several decades," said Gerald Gabrielse, who led the research at Northwestern. "But our finding is still just as scientifically significant because it strengthens the Standard Model of particle physics and excludes alternative models."

[...]In addition to Gabrielse, the research was led by John Doyle, the Henry B. Silsbee Professor of Physics at Harvard, and David DeMille, professor of physics at Yale. The trio leads the National Science Foundation (NSF)-funded Advanced Cold Molecule Electron (ACME) Electric Dipole Moment Search...

Continue reading at https://phys.org/news/2018-10-standard-particle-physics-excludes-alternative.html#jCp. Also read the research article: ACME Collaboration, "Improved limit on the electric dipole moment of the electron," Nature (2018) doi: 10.1038/s41586-018-0599-8.