Elsevier

Nuclear Physics A

Volume 480, Issues 3–4, 11–18 April 1988, Pages 547-572
Nuclear Physics A

Knockout of 1p protons from 12C induced by the (e, e'p) reaction

https://doi.org/10.1016/0375-9474(88)90463-0Get rights and content

Abstract

The reaction 12C(e, e'p)11B has been studied in parallel kinematics at an outgoing-proton energy of 70 MeV. The momentum distributions for 1p knockout measured in the range of missing momentum −170 ⩽ pm ⩽ 210 MeV/c are compared to DWIA calculations employing various prescriptions for the final-state interaction. It is found impossible to obtain simultaneously a good description of the data at positive pm, and negative pm, using a standard DWIA calculation. This discrepancy can be resolved by assuming a (15 ± 5)% enhancement of the ratio of transverse to longitudinal response functions. The effects of channel couplings in the final state of the (e, e'p) reaction have been investigated by performing CCIA calculations with a coupling scheme derived from elastic proton scattering off 12C. In elastic proton scattering an adjustment of the optical potential causes the standard optical-model calculation to be almost equivalent to the coupled-channels calculation. Similar calculations for the (e, e'p) reaction yield momentum distributions that differ from the DWIA calculations, especially in parallel kinematics. The influence of the channel couplings on the derived spectroscopic factors is relatively small for the ground state (≈1%), but can be as large as 30% for the excited states. We find a spectroscopic strength for 1p knockout from 12C of (57 ± 6)% of the IPSM sum-rule assuming that the longitudinal part of the virtual-photon proton coupling is not modified. The rms radii of the proton 1p orbitals as deduced from the measured momentum distributions are consistent with those derived from elastic magnetic electron scattering.

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    Present address: Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

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