Development of a cold atomic muonium beam for next generation atomic physics and gravity experiments

A high-intensity, low-emittance atomic muonium (M =μ^+ + e^- = μ + + e − ) beam is being developed, which would enable improving the precision of M spectroscopy measurements, and may allow a direct observation of the M gravitational interaction. Measuring the free fall of M atoms would be the first test of the weak equivalence principle using elementary antimatter ( μ^+ μ + ) and a purely leptonic system. Such an experiment relies on the high intensity, continuous muon beams available at the Paul Scherrer Institute (PSI, Switzerland), and a proposed novel M source. In this paper, the theoretical motivation and principles of this experiment are described.