Measurement of the Permanent Electric Dipole Moment of the ${}^{129}$Xe Atom

Abstract

We report on a new measurement of the CP-violating permanent Electric Dipole Moment (EDM) of the neutral ${}^{129}$Xe atom. Our experimental approach is based on the detection of the free precession of co-located nuclear spin-polarized ${}^3$He and ${}^{129}$Xe samples. The EDM measurement sensitivity benefits strongly from long spin coherence times of several hours achieved in diluted gases and homogeneous weak magnetic fields of about 400~nT. A finite EDM is indicated by a change in the precession frequency, as an electric field is periodically reversed with respect to the magnetic guiding field. Our result, $\left(-4.7\pm 6.4\right)\cdot 10^{-28}$ ecm, is consistent with zero and is used to place a new upper limit on the ${}^{129}$Xe EDM: $|d_{\text{Xe}}|<1.5\cdot 10^{-27}$ ecm (95% C.L.). We also discuss the implications of this result for various CP-violating observables as they relate to theories of physics beyond the standard model.