Atomic Parity Violation and the Nuclear Anapole Moment

In 1957, T. D. Lee and C. N. Yang received the Nobel Prize in physics for their discovery that the basic forces of nature distinguish slightly between left and right. This parity violation means that in another universe, identical to our own but mirror-reversed, the laws of physics would be slightly different. In his Perspective, Haxton describes results presented in the same issue by Wood et al . ( p. 1759 ) on high-precision measurement of this fundamental symmetry principle in cesium atoms. At the same time, the experiments have provided the first measurement of a long-sought phenomenon called the anapole moment, which results from parity violation coupling to an electromagnetic field. The precision of these observations is such that they now offer tests of the standard model of particle physics.