Order of Magnitude Smaller Limit on the Electric Dipole Moment of the Electron

The Standard Model (SM) of particle physics is known to be incomplete. Extensions to the SM, such as weak-scale Supersymmetry, posit the existence of new particles and interactions that are asymmetric under time-reversal (T), and nearly always predict a small, yet potentially measurable (10 −27 -10 −30 e cm) electron electric dipole moment (EDM, (EDM, d e ). The EDM an asymmetric charge distribution along the spin ( S → ) that is also asymmetric under T. Using the polar molecule thorium monoxide (ThO), we measure d e = (–2.1 ± 3.7 stat ± 2.5 syst ) × 10 −29 e cm. This corresponds to an upper limit of | d e | −29 e cm with 90 percent confidence, an order of magnitude improvement in sensitivity compared to the previous best limit. Our result constrains T-violating physics at the TeV energy scale.