The transition amplitude for ($p,2p$) reactions initiated by protons with energies in excess of 100 MeV is cast into a form which facilitates identification of components associated with the standard (direct) knockout mechanism, and with semidirect processes in which excited states of the target, notably the giant resonances, mediate the transitions. Calculations of both direct and semidirect amplitudes are presented, for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(p,2p)\mathrm{}$ reaction, in an asymmetric energy-sharing geometry for which a half distorted-wave approximation is appropriate. Estimates of the semidirect effects, using coupling strengths deemed appropriate from analyses of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(p,p^{\prime })$ data, indicate that under favorable kinematic conditions such effects should be discernable in correlations.

NUCLEAR REACTIONS Scattering theory including resonance effects, applied to ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(p,2p)\mathrm{}$ asymmetric energy-sharing geometry, $E=98.7\mathrm{}$ MeV; calculated $\sigma \left(\theta \right)$; optimal resonance effects estimated.

• Received 9 May 1980

DOI:https://doi.org/10.1103/PhysRevC.23.1