Energetic Charged-Particle Spectrum Followingμ−capture by Nuclei

The energy spectra of charged particles (mainly protons) emitted following muon capture have been measured for targets of Al, Cu, and Pb. The intensity of the energetic (40-70 MeV) emitted particles falls exponentially with increasing energy, $I={I}_{0}\mathrm{exp}(\ensuremath{-}\frac{E}{{E}_{0}})$, with exponential constant ${E}_{0}$ 7.5\ifmmode\pm\else\textpm\fi{}0.4 MeV (Al), 8.3\ifmmode\pm\else\textpm\fi{}0.5 MeV (Cu), 9.9\ifmmode\pm\else\textpm\fi{}1.1 MeV (Pb). The integrated yield for particles above 40 MeV was found to be (1.38\ifmmode\pm\else\textpm\fi{}0.09)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ per capture for Al, (1.96\ifmmode\pm\else\textpm\fi{}0.12) \ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ per capture for Cu, and (0.171\ifmmode\pm\else\textpm\fi{}0.028)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ per capture for Pb.NUCLEAR REACTIONS Al, Cu, Pb (${\ensuremath{\mu}}^{\ensuremath{-}}$,$x$), $E=0$, measured charged particle spectrum, $\ensuremath{\sigma}(E)$.