Figure 1:  Semi-logarithmic plot of the phase space within the pion decay region for the original 150 MeV/c pions and muons generated through the subsequent normal and hypothetical pion to muon decay modes including the radiative decay mode.  Relative to the pions (indicated in green) and the muons from the hypothetical decay mode (indicated in red), the normal and radiative pion decay modes are scaled by factors of 10² and 10⁶, respectively.