Kinematically complete measurement of the (π±,π±p) reaction onC12at 220 MeV

Abstract

The $^{12}\mathrm{C}({\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}},{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}\mathrm{p})$ reactions were studied at ${T}_{\ensuremath{\pi}}=220$ MeV. The final particles were detected both separately and in coincidence and their momenta were measured. Calculation of the excitation energy of the residual nucleus allowed clear separation of events where an outer proton was removed. The data provide detailed evidence confirming the quasielastic picture of pion knockout reactions. Evidence for this derives from the agreement between the peak energies found in the coincidence spectra and those found in inclusive spectra, from analysis of angular distributions, and from the location of peaks found in missing mass spectra. The coincidence cross section is found to account for about half of the (${\ensuremath{\pi}}^{+}$,${\ensuremath{\pi}}^{+\ensuremath{'}}$) reaction, and about half of this in turn corresponds to quasifree knockout of the outer shell protons. Secondary processes in the (${\ensuremath{\pi}}^{\ensuremath{-}}$,${\ensuremath{\pi}}^{\ensuremath{-}}\mathrm{p}$) reaction are found to play a much more important role than in the (${\ensuremath{\pi}}^{+}$,${\ensuremath{\pi}}^{+}\mathrm{p}$) reaction.