Measuring the electron electric dipole moment using laser-cooled cesium atoms in optical lattices.

摘要

Discrete symmetries have played a vital role in the development of the standard model of particle physics. Electric dipole moments (EDM's) of elementary particles are sensitive probes of discrete symmetry violations. The standard model predicts a permanent electron electric dipole moment (eEDM) that is 10--37 ∼10--38 e · cm. Most proposed standard model extensions, like supersymmetry, predict a larger eEDM that is comparable to or slightly smaller than the current experimental limit, |de| ≤ 1.05 x 10 -27 e · cm. Observation of a permanent eEDM in the foreseeable future would imply new CP violating effects not captured by the standard model. This dissertation is a project report of the Penn State eEDM search using laser-cooled Cesium atoms in optical lattices. In particular, I will describe experimental progress in apparatus development, quantum state preparation and state-selective fluorescence detection, and magnetometry using Larmor precession of spin-polarized atoms. I will also describe theoretical studies of low frequency spectroscopy that will be used in the eEDM measurements. In our experiment, Cesium atoms are guided into a measurement chamber, where they are laser-cooled and trapped in a pair of far-detuned, high quality linearly polarized, parallel one-dimensional optical lattices. The lattice beams thread three specially coated fused silica electric field plates. The measurement chamber is passively shielded by a four layer mu-metal magnetic shield, inside of which eight magnetic field coils actively control the bias and gradient magnetic fields, based on sensitive atomic magnetometry measurements. A series of high fidelity microwave adiabatic fast passage pulses and specially engineered low frequency magnetic pulses transfer the atoms into a superposition state that is sensitive to the eEDM signal. Combining unprecedented precision made possible by cold atoms with engineering, our experiment has a projected precision that is 400-fold improvement of the current measured limit.