Existing cross-section data for 1p-shell knockout in the reaction 12C(e,e'p)
- as obtained under different kinematic conditions - are shown to be mutually
consistent, apart from a recent measurement performed in Mainz. New data have
been collected at the Amsterdam Pulse Stretcher that confirm the normalization
of the older measurements. An analysis of the world's 12C(e,e'p) data has
yielded precise values of the spectroscopic factor for 1p-shell and 1s-shell
knockout from 12C. These values have been used to evaluate the transparency of
the 12C nucleus for 1p-shell and 1s-shell protons separately on the basis of
recent high-energy 12C(e,e'p) data taken at a four-momentum transfer squared of
1.1 GeV/c^2. As the resulting average value of the nuclear transparency,
0.81(0.04), is considerably higher than the value obtained from previous
analyses and theoretical estimates, the high Q^2 data were used instead for an
independent determination of the spectroscopic strength for 1p + 1s knockout.
Combining these results with the low Q^2 data the spectroscopic factors appear
to be momentum-transfer dependent. Possible explanations of these surprising
results in terms of reaction-mechanism effects or a possible breakdown of the
quasi-particle concept at high Q^2 are discussed as well.Comment: 11 pages 8 figure
