An experiment will be pursued to search for the electric dipole moment (EDM) of the electron using cold cesium and rubidium atoms. The apparatus will be appropriately modified based on what has been learned over the last three years, and then EDM data collection will commence. The experiment uses atoms launched and 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. EDMs will be measured by observing coherent atom evolution in electric fields that are directed oppositely in the two traps. It is projected that the experiment will be sensitive to an EDM as small as 3x10-30 e-cm, which is a 300-fold improvement over the current limit.
A particle with a permanent EDM implies that both time-reversal invariance and parity invariance are violated. Both of these symmetries are in fact violated in the standard model of physics, which predicts very small, but non-zero EDMs for fundamental particles. Proposed extensions to the standard model tend to predict much larger EDMs, close to the current experimental upper limit. Continued non-observation of EDMs would rule out many possible extensions to the standard model. Conversely, should an EDM be observed, it would be the first experimental result of any kind that cannot be incorporated into the standard model of physics. If an EDM is found in an atom or molecule, the extraction of the fundamental physics will be far more reliable in the alkali atoms used in this experiment than in other more complicated atoms or molecules. This experiment addresses a question of fundamental importance to elementary particle physics. Such questions are normally addressed with high energy experiments, but in this case the precision tools of atomic physics can be applied to a much lower energy system, with a concomitant lower cost. Undergraduates and graduate students will be trained in the experimental research methods and develop skills preparing them for the nation's scientific work force.
