Tracks of Pion and Muon in the end of their range

 

Picture of negative muon at the end of their range (below, left) : Muon are identified by the presence of the tracks of associated fast electron starting from the end of their range (see below, tracks b and d). The pronounced scattering of the particles, as compared with protons, allows the tracks to be distinguished easily. The rate of loss of energy varies from about 7 keV/μm where a track enters the field of view, to 25 keV/μm, 10 μm from the end of the range, without producing any clearly marked change in the density of grains in the tracks. Large deviations due to scattering are, however, clearly more frequent towards the end of the range.

Picture of negative pion at the end of their range (upper, right) : Short lengths of the tracks of π and μ cannot be distinguished by inspection, but the effects at the end of the range are commonly decisive. Negative pion produce characteristic nuclear disintegrations at the end of their range. Very rarely μ produce ‘two-prong’ star following nuclear capture. Positive pion, which can’t approach a nucleus due to the electrostatic repulsion and make nuclear disintegration, decay into a muon with a range of 600 μm in emulsion (4,12 MeV kinetic energy). Positive muon decays into an electron when it reaches the end of its range. Sometimes, however, no secondary tracks appear from the ends of the range of π and μdue to lack of well-developed electron sensitive emulsion.