Measurement of the permanent electric dipole moment of the Xe129 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, (−4.7 ± 6.4) · 10 −28 ecm, is consistent with zero and is used to place a new upper limit on the 129 Xe EDM: |dXe| < 1.5 · 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.

Continuous comagnetometry using transversely polarized Xe isotopes

“…For detection of non-magnetic spin-dependent interactions the sensing bandwidth is 1 Hz, the white-noise level is 7 µHz / √ Hz, and the bias instability is ≈ 1 µHz.Spin-exchange (SE) pumped comagnetometers [1, 2] utilize co-located ensembles of spin-polarized alkali-metal atoms and noble gas nuclei [3] to suppress magnetic field noise. Such devices have been used to place upper bounds on spin-mass couplings [4,5], Lorentz violations [6-10], and atomic electric dipole moments [11][12][13], and for the measurement of inertial rotation [2,[14][15][16]. The fundamental uncertainty of a SE pumped comagnetometer's measure of inertial rotation scales favorably with sensor size compared to alternative technologies [17].Longitudinal SE fields are important sources of systematic uncertainty in devices which utilize the embedded alkali-metal atoms for high SNR detection.…”

“…Spin-exchange (SE) pumped comagnetometers [1,2] utilize co-located ensembles of spin-polarized alkali-metal atoms and noble gas nuclei [3] to suppress magnetic field noise. Such devices have been used to place upper bounds on spin-mass couplings [4,5], Lorentz violations [6][7][8][9][10], and atomic electric dipole moments [11][12][13], and for the measurement of inertial rotation [2,[14][15][16]. The fundamental uncertainty of a SE pumped comagnetometer's measure of inertial rotation scales favorably with sensor size compared to alternative technologies [17].…”

Electro-optic sensor for static fields

“…Such methods are difficult or even impossible to apply in several of the EDM experiments, which are presently underway. We report here on the measurement of static electric fields inside a closed glass measurement cell placed inside the field of an external electrode system as well as on the development of an electro-optic field sensor based on a LiNbO 3 crystal in the context of an EDM search on 129 Xe atoms [8,9]. The sensor provides for reliably measuring and continuously monitoring a static electric field during periods of several hours.…”

Search for electric dipole moments

“…Elaborate atomic, molecular and nuclear calculations are required to account for these contributions. Similarly, when using diamagnetic atoms like 199 Hg [16] or 129 Xe [18,23] nuclear theory is required to extract the CP-violating parameters at the hadronic level, such as the nucleon EDM and CP-violating pion-nucleon couplings, while atomic theory is needed for the extraction of the scalar and tensor couplings of the electron to the nucleons.…”