ABSTRACT
Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 15.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
The studies of the parity nonconservation (PNC) effects in atoms began in the 1970s as soon as the standard model (SM) of the electroweak interactions was introduced [1,2]. The first proposals for the atomic PNC experiments were provided in [3] (optical dichroism, Cs atom) and in [4] (optical rotation, Tl, Bi, and Pb atoms). The first observation of the PNC effect in atoms (optical rotation, Bi) was reported in Novosibirsk [5], and the most accurate recent experiment belongs to the Boulder group [6] (Cs atom, optical dichroism). The accuracy of the latter experiment reaches 0.5% that allows also for the observation of the small nuclear-spin-dependent PNC contribution caused by the anapole moment of the nucleus [7,8]. The atomic PNC experiments are indirect, that is, they require adequate theoretical description to extract the SM constants from the experimental data. To describe the PNC effect in the heavy many-electron atom with the required accuracy (better than 0.5%) appeared to be very hard problem. Due to the very short radius of the weak
Ion
interactions, the PNC effects are proportional to the density of the valence electrons at the nucleus surface. Then the electron correlation between all 55 electrons in the Cs atom is involved. Moreover, the relativistic Breit interaction also appeared to be significant as well as quantum electrodynamical (QED) effects: vacuum polarization and electron self-energy corrections. The modern status of the problem is presented in detail in [9] (see also the most accurate latest calculation of QED corrections to the PNC effects in Cs in [10]). Still not all the electroweak radiative corrections to the PNC effects in heavy atoms are included, and the agreement of the atomic PNC experiments with the SM based on the high-energy determination of the free parameters requires further approval. The use of heavy atoms is necessitated by the Z3
enhancement of the PNC effects with the growth in the nuclear charge Z. It is, therefore, greatly attractive to use much simpler systems such as the
highly charged ions (HCIs) with high Z values for the search of PNC effects in atomic physics. A number of proposals [11-18] were made during the last decades for the search of PNC effects in HCIs. In this chapter, we will discuss the recent status of the problem and the most prominent ways for its solution.
For the description of the PNC effects in heavy atoms and HCIs, it is necessary to use the fully relativistic theory for the electrons. However, the nucleons within the nuclei can be considered as nonrelativistic. This follows from the order of magnitude of the energies involved: these energies can be as large as the rest energy of the electrons mec2, where me is the electron mass and c the speed of the light, but essentially lower than that of the nucleons. Within this approximation, the effective relativistic Hamiltonian of the interaction between the atomic electron and the nucleus is [9]
