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, 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.