An ultracold beam of YbF molecules for measuring the electron’s electric dipole moment

Abstract

The observed matter-antimatter asymmetry of the universe remains unexplained and undiscovered sources of CP violation could yet prove to be its source. The electric dipole moment of leptons, strongly suppressed in the Standard Model, would be a source of CP violation and a sign of new physics. Recent measurements of the electron EDM have already pushed constraints on the energy range for new particles to be discovered beyond the reach of the LHC.

This work focuses on the progress towards an experiment to measure the electron EDM using YbF. A buffer gas-cooled molecular source generates a pulsed beam of YbF molecules travelling at 180 m/s. Employing two-dimensional laser cooling, the transverse temperature of the beam drops below 200μK, significantly increasing its brightness by over two orders of magnitude compared to the uncooled beam. On average, each cooled beam pulse contains approximately 2x10^5 ultracold molecules. A hexapole magnetic lens will guide the molecular beam towards the cooling lasers. Simulations predict that the lens will enhance beam brightness by at least five-fold. Combined with transverse laser cooling, this magnetic lens has the potential to yield a beam three orders of magnitude brighter. This enhancement will enable a measurement of the electron EDM, with a statistical uncertainty of 2.2x10^(-31) e cm. This will represent an improvement of over an order of magnitude compared to the recent record established by JILA. Lastly, a new optical pumping scheme has been developed to transfer molecules from their laser cooling state to the absolute ground state of YbF, preparing for electron EDM measurement. This work lays the foundation for a high-precision measurement of the electron EDM using YbF.