Observation of Migdal’s Effect in the Decays of Positively Charged Pions and Muons

The energy spectra of fast (101−102 keV) electrons accompanying π+ → μ+ decays of positively charged pions (π+) stopped in a nuclear emulsion are obtained. These spectra are compared with the analogous spectra obtained earlier for electrons accompanying the decay μ+ → е+. The comparison in question confirms qualitatively the hypothesis that, in either process, fast electrons appear via the mechanism based on Migdal’s shakeup effect.