Hunting for a Fundamental Shift in Physics: China’s MACE Experiment
An ambitious new experiment, known as MACE (Muonium-to-Antimuonium Conversion Experiment), has launched in China, aiming to probe the very foundations of particle physics. Led by an international team of scientists from Sun Yat-sen University and the Institute of Modern Physics of the Chinese Academy of Sciences, MACE seeks to observe a highly improbable event: the spontaneous transformation of muonium into its antimatter counterpart, antimuonium. The experiment, detailed in a release, represents a significant leap forward in the search for physics beyond the Standard Model.
Muonium is a short-lived exotic atom consisting of a positive muon and an electron. Antimuonium is its antimatter equivalent. The Standard Model of particle physics dictates a principle called lepton flavor conservation, which, if unbroken, prevents this type of spontaneous conversion. Observing muonium transforming into antimuonium would therefore be a groundbreaking discovery, signaling the existence of new forces or particles operating at energy scales currently beyond our reach.
A Unique Probe of New Physics
The research team emphasizes that this potential conversion offers a “clean and unique probe of new physics in the leptonic sector.” Unlike other experiments searching for violations of lepton flavor, MACE is designed to be sensitive to a specific type of interaction – ∆Lℓ = 2 models – that could reveal phenomena inaccessible to other experimental approaches. This sensitivity is key to exploring potential extensions to the Standard Model.
Building on Past Efforts, Aiming for Unprecedented Sensitivity
The search for this conversion isn’t new. The last dedicated experiment to look for this effect was conducted in 1999 at the Paul Scherrer Institute in Switzerland. MACE, however, is designed to dramatically improve upon those previous results. The team aims to increase the experimental sensitivity by more than a hundredfold, targeting a conversion probability as low as O(10-13). This represents a substantial technological challenge, requiring advancements across the entire experimental setup.
Achieving this level of sensitivity necessitates a suite of cutting-edge technologies. These include a high-intensity surface muon beam, a novel silica aerogel target, and a high-precision detector system. The design focuses on isolating the extremely faint signal of antimuonium formation from background noise, making MACE one of the most sensitive low-energy experiments currently searching for lepton flavor violation.
What Could a Positive Result Mean?
If MACE were to detect the muonium-to-antimuonium conversion, the implications would be profound. It would open a window into physics at energy scales ranging from 10 to 100 TeV. This is comparable to, or even exceeds, the energy levels expected to be probed by future particle colliders, potentially offering a complementary path to understanding the universe at its most fundamental level.
Beyond the primary search for muonium-to-antimuonium conversion, MACE is also planned to operate in a Phase I stage dedicated to investigating other rare muonium decay processes and lepton flavor violating events, such as M→γγ and μ→eγγ, with record-breaking sensitivity. This multi-faceted approach maximizes the experiment’s potential for discovery.
Beyond Fundamental Physics: Technological Spin-offs
The impact of MACE extends beyond the realm of fundamental physics. The development of advanced technologies for the experiment – including innovative muonium production targets, low-energy positron transport systems, and high-resolution detectors – could have applications in other fields. Potential benefits are seen in materials science and medical research, demonstrating the broader societal impact of basic scientific inquiry.
Part of a Larger Scientific Initiative
MACE is not an isolated project but is part of a larger scientific push centered around major research facilities in Huizhou, China. These facilities include the High-intensity heavy-ion Accelerator Facility (HIAF) and the China initiative Accelerator Driven System (CiADS). The combined effort aims to establish China as a global leader in high-precision nuclear and particle physics. By leveraging these advanced facilities, MACE exemplifies how fundamental research can drive both technological progress and international collaboration.
As the research team succinctly puts it, “We are not just building an experiment; we are opening a new window into the laws of nature.” Every aspect of MACE, from the beamline to the software, has been meticulously optimized to explore physics that could fundamentally reshape our understanding of matter, symmetry, and the universe itself. The experiment represents a bold step in the ongoing quest to unravel the mysteries of the cosmos.
