Progress toward a search for a permanent electric dipole moment in liquid xenon-129.

摘要

Here we report progress toward the measurement of a permanent electric dipole moment (EDM) in hyperpolarized liquid 129Xe which violates invariance under both parity and time reversal. The standard model (SM) predicts atomic EDMs well beyond current experimental limits while many natural extensions to the SM predict EDMs within the expected sensitivity of current experiments. Hence the search for a non-zero EDM is viewed as an ideal test for new physics.; Liquid 129Xe is an attractive medium in which to perform such a search because it has a high number density and a high electric field breakdown strength. For experimentally realizable parameters it should be possible to achieve a sensitivity of ∼10-32 e-cm for one day of integration; several orders of magnitude beyond current experimental limits on EDMs.; In preparation for performing a search for an EDM in liquid xenon, we have conducted a thorough experimental and theoretical investigation of the spin dynamics of hyperpolarized liquid 129Xe. In a highly polarized liquid magnetic dipolar interactions can strongly influence spin precession. For small tip angles of the magnetization away from the holding field, the system is insensitive to perturbations, leading to extended free induction decays. For large tip angles the system develops a dynamical instability so that spin precession due to a small magnetic field gradient is amplified exponentially relative to the non-interacting case. In principle; this amplification can be quite large, leading to enhanced sensitivity of spin precession measurements when noise in the detection system is much greater than spin-projection noise.; Experimentally, we have achieved amplification of spin precession due to a small applied field gradient by a factor of 9.5 relative to the non-interacting case in the large tip angle regime. Considerable improvement is expected with further optimization of high order gradients. In the small tip angle regime we have realized an extension of the free induction decay by up to a factor of 100 compared to the non-interacting case. We discuss how these two different regimes can be used in a search for an EDM in liquid xenon and analyze the expected sources of systematic effects.