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

A high-intensity, low-emittance atomic muonium (M

=\mu^+ + 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 (\mu^+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.