Search for a permanent electric dipole moment (EDM) of the 129Xe atom

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In this proposal an upgrade of the experiment for the measurement of the time-reversal violating permanent electric dipole moment (EDM) of the isotope 129-Xe is presented, which aims to improve the present experimental limit of 1,5E-27 ecm (95% CL) by more than 2 orders of magnitude. Measurements of EDMs have already excluded a variety of theories that go beyond the Standard Model of particle physics. The best limit for such an EDM was measured on the diamagnetic atom 199Hg with a value of 7,4E-30 ecm). To become more precise in measurement accuracy, a 3-He/129-Xe clock comparison experiment is performed based on free precession of the two nuclear spins. The spin precession is detected by SQUID sensors. The decisive improvements will be achieved with a new magnetically shielded room which permits longer spin coherence times (~1 day) and a significantly improved signal-to-noise ratio. Since both gases occupy the same volume, the magnetic field dependence in the difference of their Larmor frequencies is eliminated (co-magnetometry) and thus many systematic errors, e.g., leakage currents, correlated with the switching of the electric field. Thus, one is only sensitive to non-magnetic interaction terms, here of the type: The measured frequency shift is proportional to the applied electrical filed strength and the electric dipole moment of 129-Xe.