Physicists at the Japan Proton Accelerator Research Complex (J-PARC) have irradiated positive muons to water or a plastic scintillator block and imaged them using a charge-coupled device camera. An optical image of plastic scintillator during irradiation of 73.9-MeV/c positive muons. Image credit: Yamamoto et al., doi: 10.1038/s41598-020-76652-8. A muon is a particle similar to an electron, with an electric charge of e− for a negative muon and e+...