Searching for electric dipole moments

Abstract

Searches for a permanent Electric Dipole Moment (EDM) of a fundamental particle provide a wide window for the discovery of potential New Physics. Within todays Standard Model in particle physics the well established violation of CP symmetry gives rise to EDMs which are several orders of magnitude below the present experimentally established upper bounds. On the other hand, EDMs appear quite naturally within many modern speculative theories, which have been suggested to improve the known shortcomings of the present Standard Model, e.g., the lack of giving reasons for certain established facts such as the mass hierarchy of the fundamental fermions or the number of three particle generations. They could be almost as large as the present experimental bounds. The speculative models provide for EDMs of different fundamental particles in specific ways. As there is no convincing indication, yet, which of the various extensions to the present standard theory may be more successful, a larger number of EDM searches is very well motivated. Still, even with the discovery of an EDM in one system several experiments will be required to pin down the precise nature and the underlying processes. Therefore searches are going on presently in a variety of systems, ranging from free leptons to complex condensed matter samples. These experiments utilize typically state of the art precision measurements which are often based on forefront technological developments. The experimental efforts are complemented and guided by the further development and refinement of particle theory. Here a few aspects of recent developments in this exciting field are summarized.

Experimental search for the electron electric dipole moment with laser cooled francium atoms

“…The EDM search is being performed and planned in various types of particles, such as neutron, diamagnetic atom, paramagnetic atom, molecule and charged particle [2]. In this report, we present an experiment to search for the electron EDM by using the laser cooled francium (Fr) atoms at Cyclotron and Radioisotope Center (CYRIC), Tohoku University.…”

Precision Tests of Discrete Symmetries at Low Energies

“…Along with the ever increasing precision in experiments numerous suggested speculative models beyond the standard theory of the time could be ruled out. At present, pressure is increasing on minimal supersymmetric models from improved limits on the EDM of various particles [6]. In fact, there is little room left in parameter space for such models.…”

“…In this context precision experiments with antiprotons [2], muons [3] or neutrons [4] are very advanced examples of accelerator or reactor based experiments at low energies, which aim to provide data and new observations towards resolving the open puzzles. Precise experiments on atomic parity violation [5] or searches for electric dipole moments on fundamental particles [6] are typically carried out in small scale laboratory experiments. Such approaches are complemented by searches for CPT or Lorentz invariance violations [7] which cover the full range of experimentally accessible energies.…”

Francium: Tool for Fundamental Symmetry Investigations

“…For a large Z this factor can provide a few orders of magnitude enhancement of the electric field inside the atom. Experimental searches for permanent electric dipole moments are in progress using various systems such as neutron, electron and nucleons through atoms and molecules [9]. Our interest is in francium (Fr), a paramagnetic atom for the electron EDM experiment.…”