A New Limit on the Electron Electric Dipole Moment

Abstract:

The electron is expected to have an electric dipole moment

(d_e), though it has so far eluded experimental observation.  While

the Standard Model's prediction for d_e is still far beyond any

foreseeable experiment, new physical theories (especially

Supersymmetry) predict values for d_e that are near the experimental

upper limit.  The ACME Collaboration recently performed a search for

d_e via a precision spin precession measurement in a beam of polar ThO

molecules [arXiv:1310.7534].  Our measurement did not see any

evidence for a non-zero d_e, but we did set the limit |d_e| <

8.7*10^-29 e*cm. This represents an order of magnitude improvement

over the previous best limit, and places tighter restrictions on new

physics beyond the Standard Model.