MACE Experiment Targets New Physics with Muonium-Antimuonium Conversion

The Muonium-to-Antimuonium Conversion Experiment (MACE), spearheaded by researchers from Sun Yat-sen University, the Institute of Modern Physics of the Chinese Academy of Sciences, and other collaborating institutions, aims to detect the spontaneous conversion of muonium into antimuonium.

This conversion would violate lepton flavor conservation, a principle of the Standard Model of particle physics, and would indicate the existence of new physics.

Such a discovery would offer a unique window into uncharted territories of the universe's fundamental laws.

Experiment Goals

The research team asserts that muonium-to-antimuonium conversion provides a distinct methodology to explore new physics within the leptonic sector. This method is particularly sensitive to ∆L ℓ = 2 models, which are not accessible by other experimental approaches. The last established experimental limit for this conversion dates back to 1999.

MACE intends to improve upon this limit by over two orders of magnitude, targeting a conversion probability of O(10-13).

Technological Innovations

Achieving this unprecedented sensitivity necessitates significant advancements across the entire experimental setup. Key innovations include:

• A high-intensity surface muon beam.
• A novel silica aerogel target.
• A high-precision detector system.

The team emphasizes that the design expertly integrates advanced beam technology, specialized muonium production target mechanisms, and sophisticated detector systems. This comprehensive approach is crucial for isolating the signal from substantial backgrounds, positioning MACE as a highly sensitive low-energy experiment for lepton flavor violation.

Broader Implications and Future Scope

Should the experiment prove successful, MACE holds the potential to investigate new physics at energy scales reaching 10–100 TeV. These energy levels are comparable to, or even surpass, the capabilities of proposed future colliders. A planned Phase-I stage of the experiment is also set to search for other rare muonium decays and lepton flavor violating processes, such as M→γγ and μ→eγγ, with enhanced sensitivity.

Beyond fundamental physics, the technologies developed for MACE, including the muonium production target, low-energy positron transport system, and high-resolution detectors, could find practical applications in fields like materials science and medicine. MACE is a cornerstone of a broader scientific initiative at Huizhou's scientific facilities, which also encompasses the High-intensity heavy-ion Accelerator Facility (HIAF) and the China initiative Accelerator Driven System (CiADS). This larger endeavor seeks to significantly advance China's standing in high-precision nuclear and particle physics.