Let’s look at a seemingly simple measurement: the charge radius of the proton, which is a measure of its physical size. Measurements made with hydrogen atoms, which have a single electron orbiting a proton, gave us one answer. Measurements in which the electron was replaced by a heavier particle, called a muon, gave us a different answer—and the two results were incompatible. A lot of effort has gone into eliminating this discrepancy, and it has gotten smaller, but it hasn’t gone away. Only recently have scientists been able to develop a positively charged ion, comprised of a helium nucleus and a single orbiting muon. No easy task. It was important to find a way to generate a large scale amount of these atomic particles to have enough to use in the correct state and within a time frame that would ensure results before the muon degenerated.
Key Takeaways:
- Problems arose as muons are unstable and typically decay in under two microseconds.
- Researchers had access to a beam of muons created by a particle collider, and they decided to direct the beam into some helium gas.
“Muons are essentially heavy versions of electrons, so substituting one for another in an atom is relatively simple.”
