Production of the Smallest QED Atom: True Muonium (mu^+ mu^-)

Understand

The "true muonium" (mu^+ mu-) and "true tauonium" (tau^+ tau^-) bound states are not only the heaviest, but also the most compact pure QED systems.

• The rapid weak decay of the tau makes the observation of true tauonium difficult.
• However, as we show, the production and study of true muonium is possible at modern electron-positron colliders.