Nuclear structure and the search for collective enhancement of {\cal P\hbox{,}T} -violating Schiff moments

Abstract

The search for the manifestations of new physics beyond the standard model in atomic and nuclear phenomena is pursued by several experimental groups. The discovery of the atomic electric dipole moment (EDM) would reveal the simultaneous violation of parity (P) and time-reversal (T ) invariance. The EDM can be induced by T -odd forces between the nucleus and atomic electrons. As the nuclear dipole moment is screened according to the Schiff theorem, the appropriate nuclear operator is the Schiff moment that may exist in nuclei under PT -violation. We briefly review the current experimental situation and discuss more in detail the ideas concerning possible collective mechanisms for the enhancement of the nuclear Schiff moment. The most promising directions are related to the coexistence of octupole and quadrupole collective modes, either in the form of static deformation or as soft vibrational excitations. The search for enhancement is important for widening the pool of nuclei as candidates for the atomic EDM as well as for development of nuclear many-body theory beyond standard mean-field and random phase approximations.

Quantum chaos and thermalization in isolated systems of interacting particles

“…This independence confirms that the enhancement is generated in the compound nucleus, prior to the choice of a certain decay channel by a fissioning nucleus. For more details concerning the violation of fundamental symmetries and chaotic enhancement we refer the reader to review articles [101,102,104]. There are also numerous examples of chaotic enhancement in tunneling or mixing of very different configurations in many-body systems that occur at close energies, for example different shapes [105] or long-lived isomers [106].…”

Pseudo‐Hermitian random matrix theory

“…In line with the theme of the Special Issue is atomic electric dipole moment, the discovery of which Copyright line will be provided by the publisher will be an instance of breakdown of parity and time-reversal symmetries. In certain nuclei with shapes that would support such a symmetry-scenario, it is expected that certain collective modes would enhance the Schiff moment [42]. The quadrupole and octupole collective modes could co-exist.…”

Dipole resonances and the nuclear Schiff moment

“…Since the mean value of the nuclear dipole moment D is screened in the atom, the atomic electric dipole moment is generated by the nuclear Schiff moment [see the recent reexamination of the Schiff theorem in [18,19]],…”

“…The same techniques can be used for the choice of the Schiff moment (6) as the dipole operator (16) acting with the weak interaction. The normalization (19) can be found now as (Ŝ|Ŝ) = 8 315 4πe 2 R 9 p x 2 .…”