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, de). The EDM is an asymmetric charge distribution along the spin that is also asymmetric under T.

About five years ago, ACME, a collaboration between groups at Yale and Harvard universities (http://www.electronedm.org), embarked upon an improved search for the electron EDM. Using the polar molecule thorium monoxide (ThO), we have now measured de =(-2.1+-3.7stat +-2.5syst) X 10-29 e.cm. This corresponds to an upper limit of |de| < 8.7 X 10-29 e.cm with 90 percent confidence, an order of magnitude improvement in sensitivity compared to the previous best limits. Our result constrains T-violating physics at the TeV energy scale.