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

## TL;DR

This paper presents a highly sensitive experiment measuring the electric dipole moment of $^{129}$Xe, setting new upper limits and contributing to understanding CP violation beyond the Standard Model.

## Contribution

The study introduces a novel measurement technique using co-located $^3$He and $^{129}$Xe spins with long coherence times, achieving improved sensitivity in EDM detection.

## Key findings

- Measured $^{129}$Xe EDM: $(-4.7 imes 10^{-28}) ext{ ecm}$ with uncertainty
- Set a new upper limit on $^{129}$Xe EDM: $|d_{Xe}| < 1.5 imes 10^{-27} ext{ ecm}$ (95% C.L.)
- Results have implications for theories of CP violation beyond the Standard Model

## 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, $\left(-4.7\pm6.4\right)\cdot 10^{-28}$ 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.