Search for the Electron EDM Using Cs and Rb in Optical Lattice Traps

点击翻译按钮获取中文摘要

The existence of an elementary particle with a permanent electric dipole moment (EDM) would imply that the basic equations of physics are different when time is reversed or all spatial coordinates (parity) are inverted. Although these symmetries are an integral part of classical physics, both are known to be violated in the current "Standard Model" of particle physics. In fact, there have been many direct observations of parity violation, and several indirect measurements of time reversal symmetry breaking. EDMs, however, have yet to be observed. The major motivation for trying to observe EDMs is that most proposed extensions to the Standard Model (such as supersymmetry) predict EDMs that are in the vicinity of the current experimental upper limit, whereas the Standard Model predicts that they should be much smaller. Increasing the precision of experiments could rule out possible extensions to the Standard Model, or provide the first experimental result that cannot be incorporated into the Standard Model. As such it would be a harbinger of a theoretical revolution. To measure the electron EDM, cesium atoms will be cooled with laser beams and trapped with light, and then their internal energy states will be measured in a very large electric field in a very low magnetic field environment. Undergraduates and graduate students will be trained in the use of these tools, which have many applications beyond this measurement.The electron EDM will be searched for in this experiment using laser-cooled cesium atoms. The apparatus construction part of the experiment will be completed and data collection will commence. In the experiment, atoms are loaded into a pair of parallel one-dimensional far-off-resonant optical lattice traps in a magnetically shielded region of space, laser-cooled and optically pumped. Similar to the way permanent magnetic dipole measurements are routinely measured by looking for linear Zeeman energy shifts in magnetic fields, the EDM will be searched for by looking for linear Stark shifts in an electric field. The experiment is designed to be insensitive to magnetic fields and magnetic field gradients by simultaneously measuring two sets of atoms that experience opposite electric fields. It is projected that the experiment will be sensitive to an EDM as small as 3x10-30 e-cm, which is a 30-fold improvement over the current limit. In parallel to making the EDM experiment fully operational, the group will perform a related technological study to try to maximize the electric fields that can be sustained with the conducting oxide coated glass plates that are used. Along the way, there are two atomic polarizability measurements that the apparatus is uniquely configured to measure with improved sensitivity. Before incorporating improved field plates, the group will likely perform these measurements, which can provide tests of atomic calculations and possible improvements to the understanding of cesium clock shifts.