Relativistic Coupled Cluster (RCC) Computation of the Electric Dipole Moment Enhancement Factor of Francium Due to the Violation of Time Reversal Symmetry

Large Long-Distance Contributions to the Electric Dipole Moments of Charged Leptons in the Standard Model

We reevaluate the electric dipole moment (EDM) of charged leptons in the standard model using hadron effective models. We find unexpectedly large EDM generated by the hadron level long-distance effect, d_{e}=5.8×10^{-40}, d_{μ}=1.4×10^{-38}, and d_{τ}=-7.3×10^{-38}  e cm, with an error bar of 70%, exceeding the conventionally known four-loop level elementary contribution by several orders of magnitude.

Laser frequency locking with 46 GHz offset using an electro-optic modulator for magneto-optical trapping of francium atoms

We demonstrate frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I₂. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr.

Transportation of a radioactive ion beam for precise laser-trapping experiments

Francium is the heaviest species among the alkali elements. Due to its properties, francium is said to be of advantage in measurements of tiny observations, such as atomic parity violation and electric dipole moment. Before executing experiments with francium, it must be produced artificially because it is one of the most unstable elements. We produced francium with the nuclear fusion reaction of an oxygen beam and gold target, ionized the produced francium through a thermal ionization process, and extracted the ion with electrostatic fields. However, the thermal ionization process is known to ionize not only an objective atom but also other atomic species. Therefore, a Wien filter was installed to analyze the composition of the ion beam and purify the beam. This allowed us to improve the beam purity from ∼10(-6) to ∼10(-3).

Radioactive ion beam transportation for the fundamental symmetry study with laser-trapped atoms

The search for the violation of the fundamental symmetry in a radioactive atom is the promising candidate for precision tests of the standard model and its possible extensions. The subtle signal arising from the symmetry violation is enhanced in heavy atoms, such as a francium (Fr). To realize high precision measurements, a large amount of radioactive isotopes is required. The Fr is produced via a nuclear fusion reaction using a melted gold target with a (18)O primary beam at Cyclotron and Radioisotope Center, Tohoku University. The maximum extraction efficiency of the Fr ion was achieved at approximately 35%. The beam line consists of an electrostatic deflector, three electrostatic quadrupole triplets to the measurement area at 10 m away from the reaction point, and several beam diagnosis systems. We optimized parameters of the beam line.

Reappraisal of the electric dipole moment enhancement factor for thallium

The electric dipole moment (EDM) enhancement factor of atomic Tl is of considerable interest as it has been used in determining the most accurate limit on the electron EDM to date. However, its value varies from -179 to -1041 in different approximations. In view of the large uncertainties associated with many of these calculations, we perform an accurate calculation employing the relativistic coupled-cluster theory and obtain -466, which in combination with the most accurate measurement of Tl EDM [Phys. Rev. Lett. 88, 071805 (2002)] yields a new limit for the electron EDM: |d(e)| < 2.0 × 10⁻²⁷e cm.