Inclusive Pion Double Charge Exchange in $^{4}$He

摘要: The pion spectra observed in the inclusive double-charge-exchange reactions $^{4}\mathrm{He}$(${\ensuremath{\pi}}^{+}$,${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$)4p and $^{4}\mathrm{He}$(${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$,${\ensuremath{\pi}}^{+}$)4n are strikingly different from those heavier nuclei, exhibiting a prominent peak at high outgoing energies. shapes of these spectra, while qualitatively consistent with two sequential single-charge-exchange processes, not yet quantitatively understood.