Fundamental physics with cold radioactive atoms

The fundamental symmetries, charge conjugation (C), parity (P) and time reversal (T), play a significant role in the Standard Model (SM) of elementary particle physics. Of these, T symmetry and the combined CP symmetry are the least well understood, and they hold valuable clues for unraveling the secrets of nature. All subatomic particles are postulated to possess an intrinsic property known as a permanent electric dipole moment (EDM). The EDM of an atom is a combination of those of each constituent particle and also CP-violating interactions between the particles. Being many-particle systems, atoms and molecules are ideal candidates for probing a rich variety of both T- and CP-violating interactions. Paramagnetic atoms, which have a single valence electron in their outer shell, are sensitive to subtle signals associated with CP violations in the leptonic sector, i.e., the EDM of the electron. At present, we are developing a high-intensity laser-cooled Fr factory at RIKEN accelerator facility in an attempt to evaluate the EDM of Fr to an accuracy of 10-30 ecm. Laser cooling is important for achieving highly accurate EDM measurements, since it allows long interaction times using an optical lattice. The current status of the laser-cooled Fr EDM experiments is presented in this paper.