Quasi-free neutron and proton knockout reactions from light nuclei in a wide neutron-to-proton asymmetry range

Abstract The quasi-free scattering reactions 11 C ( p , 2 p ) and 10,11,12 C ( p , p n ) have been studied in inverse kinematics at beam energies of 300–400 MeV/u at the R 3 B-LAND setup. The outgoing proton-proton and proton-neutron pairs were detected in coincidence with the reaction fragments in kinematically complete measurements. The efficiency to detect these pairs has been obtained from GEANT4 simulations which were tested using the 12 C( p , 2 p ) and 12 C( p , p n ) reactions. Experimental cross sections and momentum distributions have been obtained and compared to DWIA calculations based on eikonal theory. The new results reported here are combined with previously published cross sections for quasi-free scattering from oxygen and nitrogen isotopes and together they enable a systematic study of the reduction of single-particle strength compared to predictions of the shell model over a wide neutron-to-proton asymmetry range. The combined reduction factors show a weak or no dependence on isospin asymmetry, in contrast to the strong dependency reported in nucleon-removal reactions induced by nuclear targets at lower energies. However, the reduction factors for ( p , 2 p ) are found to be 'significantly smaller than for ( p , p n ) reactions for all investigated nuclei.