Polarization rotation effects due to parity violation in atoms

The authors present a study of parity (P) violating polarization rotations of atoms in external electric fields. Five different types of rotations are identified and the consequences of time reversal invariance (T) are discussed. They use the standard model of elementary particle physics, where P violation in atoms is due to exchange of the Z boson between the quarks in the nucleus and the atomic electrons. The authors consider in detail hydrogen-like systems in n=2 states, where n is the principal quantum number, especially 11H, 24He+, and 612C5+. The nominal order of magnitude of the polarization rotations is 10-11-10-12 but they discuss ways to obtain in some cases large enhancement factors of order 104. The authors show that, e.g., for 11H one could in principle observe P-violating polarization rotations as large as a few percentages, where for a statistically significant result one would need a total of 1015 polarized atoms. The authors point out that some of their P-violating polarization rotations are very sensitive to the nuclear spin-dependent part of the P-violating Hamiltonian which receives a contribution from the polarized strange quark density in polarized nuclei. Thus a measurement of P-violating polarization rotations of atoms would be of great interest in at least three respects: it would demonstrate the existence of quantum mechanical effects in atoms where P violation and T conservation interplay in a subtle way; it would allow a measurement of polarized quark densities in polarized nuclei, thus shedding light on problems associated with the open-quotes spin crisisclose quotes for the nucleons; and it would allow precision determinations of the electroweak parameters related to the Z boson exchange at very low energies. This shows again the interplay of atomic, nuclear, and particle physics in P-violating effects in atoms. 47 refs., 25 figs., 15 tabs