Electron EDM constraints via a Magneto Optical Trap with Francium atoms

by Dr Taisuke Ishikawa (Tohoku University, Sendai (Japan))

Wednesday 19 Dec 2012, 10:00 → 11:30 Europe/Rome

Direction (INFN-LNL)

Violation of CP symmetry (combined symmetry of charge  conjugation, C, and parity, P) was discovered in 1964 in the decays of the neutral K mesons. It is incorporated into the standard electroweak model as a single complex phase in the quark mixing matrix (Cabibbo-Kobayashi-“Maskawa mechanism). For a long time K mesons remained the only system in which CP-violation had been observed, until in 2001, when the collaborations BaBar and Belle detected it in the neutral B mesons. The CP-violation seen there is consistent with the standard model predictions. However, a striking problem arises from cosmology and bariogenesis. Sakharov proposed that CP-violation, present at the time of the Big Bang, is a necessary ingredient in the asymmetry of matter and antimatter. It is well-known that standard model CP-violation is insufficient to generate the level of matter-antimatter asymmetry in the Universe. Understanding the origin of CP-violation and searching for possible new sources for this symmetry breaking is therefore a fundamental problemin Physics. If CPT is a good symmetry, as it is in gauge theories, then  CP-violation is  accompanied by T (time-reversal) violation. So far there has been no direct observation of T violation(CPLEAR experiment is still disputed) and its detection is of interest in its own right. Also, detection of T-violation may shed light on the origin of CP-violation. The measurement of a permanent Electric Dipole Moment (EDM) of neutron, atom, or molecule would be direct evidence of T-violation. At the Tohoku University in Sendai (Japan) an experiment is under development to further reduce the limit on the electron EDM in a Magneto Optical Trap with  Francium atoms. A detailed discussion of the motivations and of the technical choices of the experiment will be presented.