News Picks : Measurements of an electron's electric field challenge supersymmetry
23 December 2013
Ars Technica: The electron behaves like a point particle whose electric field exhibits perfect spherical symmetry. But theoretically at least, the electron can conceivably possess an electric dipole moment (EDM)—that is, an imperfection such that the particle's charge is unevenly spread along the electron's spin axis. The team behind the Advanced Cold Molecule Electron EDM project has found that no such imperfection exists to a sensitivity 12 times smaller than had previously been measured. The researchers sent beams of thorium oxide molecules into a device where the molecules were shot with lasers to cause a specific electron-level transition in the thorium atom. (Thorium was used because its high atomic number means that the innermost electrons orbit in an extreme electric field at relativistic speeds. That combination of properties would exaggerate any imperfections in the electrons' electric fields.) The molecules then passed through an electric field. If the electron EDM exists, then the electric field would change the orientation of the electrons' spin. However, no change was measured. The sensitivity of the measurements suggests that the Large Hadron Collider at CERN should not find many of the particles predicted by supersymmetry theories that could create an electron EDM.