Studying muonium to reveal new physics beyond the Standard Model
Researchers are hoping that bad muons will spill the beans on the Standard Model of particle physics by studying an exotic atom called muonium. they use the most intense beam of low-energy muons in the world.
The muon is a heavy cousin to the electron. It may be a more appropriate description. Since its discovery triggered the words "who ordered that" the muon has been bamboozling scientists.
The muon caused trouble when it was used to measure the radius of the proton, as it gave rise to a wildly different value. The muon's surprising behavior makes it a candidate to reveal new physics beyond the standard model.
Similar to hydrogen but simpler, muonium is a positive muon formed by an electron. The positive muon of muonium has no substructure compared to hydrogen's protons.
Having an intense beam of muonium particles is one of the challenges of making these measurements very precise. It's not easy to make lots of muonium, which only lasts for two microseconds.
The Swiss Muon Source is the only place in the world where there are enough positive muons at low energy. They are going at a quarter of the light's speed when they are first produced.
Slow muons pass through a thin foil target where they pick up electrons to form muonium, at the Low Energy Muons beamline. As they emerge, Crivelli's team is waiting to investigate their properties with microwaves.
The teams were able to measure a transition between specific energy sublevels for the first time in the recent publication. The transition can be modeled very cleanly, because it is isolated from other hyperfine levels.
To obtain an improved value of an important quantity known as the Lamb shift, the ability to now measure it will facilitate other precision measurements.
The shift was explained by the introduction of the quantum theory of how light and matter interact. In hydrogen, the term "proton" is used to refer to the substructure of things.
The theory of Quantum Electrodynamics could be put to the test if an ultra-precise Lamb shift was measured in muonium. The muon is about nine times lighter than the protons.
An ultra-high precision value of the muon mass will support ongoing efforts to reduce uncertainty even further. The measurement could lead to a new value of the Rydberg constant.