MACE is a next-generation experiment…

MACE is a next-generation experiment designed to catch muonium transforming into its antimatter twin, a process that would rewrite the rules of particle physics. The last search for this effect ended more than two decades ago, and MACE plans to leap far beyond it using cutting-edge beams, targets, and detectors. A discovery would point to entirely new forces or particles operating at extreme energy scales.

Observing such a process would break a fundamental rule of particle physics called lepton flavor conservation, which is a key part of the Standard Model, and would provide direct evidence for physics beyond existing theories.