Atomic Parity Violation: Overview and Perspectives

Optical experiments have demonstrated cases in which mirror symmetry in stable atoms is broken during absorption or emission of light. Such results are in conflict with standard electromagnetic (EM) theory, but can be explained within the unified electroweak theory. Their interpretation is based on exchanges of virtual weak neutral Z_0 bosons between the electrons and the atomic nucleus. These effects were predicted to increase in heavy atoms a little faster than the cube of the atomic number. Moreover, in a highly forbidden transition, like the 6S-7S transition in cesium, the EM interaction is suppressed, leaving the Z_0 exchange a chance to show up. For achieving the determination of the Cs nucleus weak charge, Q_W(Cs), the basic experimental parameter playing in Z_0, exchange the same role as the nuclear charge in the Coulomb interaction, both experimental and theoretical hurdles had to be overcome: first, the excitation and detection of an atomic line with a transition rate about 10^{14} times less than a typical atomic rate, second, the resolution of a many(55)-body problem to extract Q_W from experiment. The progress achieved since the first determination, have now raised APV measurements to the status of a precise electroweak test. They become sensitive to physics beyond the Standard Model which may have escaped high energy investigation. Consequently, strong motivation presently exists for a second independent precise measurement and still more accurate atomic physics calculations. The same experiments provide information about parity violating nuclear forces, responsible for a chiral deformation of the nuclear magnetization, described in terms of the nuclear anapole moment. I shall present today's projects and new perspectives open by atomic radiative cooling and trapping.