location: TRIUMF
Participating Canadian institutions: TRIUMF, Manitoba
International partners: USA
The goal of the FrEDM effort is to competitively constrain a permanent electric dipole moment (EDM) of the electron, using a laser-cooled francium atom fountain supplied by an intense beam of \(^{211}\)Fr from TRIUMF. Such EDM’s break time-reversal symmetry, a key component of models to explain the excess of matter over antimatter. This experiment would be complementary to a variety of EDM experiments in the neutron and in atoms with or without spin, along with a number of particle physics experiments. High-\(Z\) francium atoms feature a high sensitivity to an EDM, low sensitivity to EDM mimicking systematic effects, and extraction of the subatomic time-reversal violating (TRV) physics to high accuracy. The experiment will be developed at LBL using stable Cs as a lower-EDM sensitivity and higher-systematic sensitivity surrogate. Following the Cs prototype, a fully developed Fr experiment can make efficient use of TRIUMF time, space and resources. The aim is a sensitivity to an electron EDM at \(\approx 1 \times 10^{-29}\) e-cm, similar to the sensitivity published by ACME’s ThO measurement, which appears attainable 1. Complementarity with particle physics results make the case for improvements particularly compelling. Among experiments that search for an electron EDM, experiments using alkali atoms and thallium are the gold standard, because their sensitivity to the electron EDM has been calculated using field theory (as has the sensitivity of the neutron to quark EDMs). That puts these quantities on the same theoretical footing as the calculations that underlie the Standard Model.
A francium version of the experiment could run and achieve design sensitivity by 2026. On the 2027-2036 horizon, with motivation depending on other advancements in the field, considerable effort would be needed to improve certain limiting systematics (e.g. Johnson noise in the mu-metal shield) for the francium atom EDM.