The Muon and the Pion
The discoveries of the muon and charged pions in cosmic-ray experiments and the discovery of the neutral pion using accelerators, 1936–51.
The detection of elementary particles is based on their interactions with matter. Swiftly moving charged particles produce ionization and it is this ionization that is the basis for most techniques of particle detection. During the 1930s cosmic rays were studied primarily with cloud chambers, in which droplets form along the trails of ions left by the cosmic rays. If the cloud chamber is in a region of magnetic field, the tracks show curvature. According to the Lorentz force law, the component of the momentum in the plane perpendicular to the magnetic field is given by p(MeV/c) = 0.300 × 10 ...