Transparency of [Formula Presented] for protons

Existing cross-section data for [Formula Presented]-shell knockout in the reaction [Formula Presented] —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 [Formula Presented] data has yielded precise values of the spectroscopic factor for [Formula Presented]-shell and [Formula Presented]-shell knockout from [Formula Presented] These values have been used to evaluate the transparency of the [Formula Presented] nucleus for [Formula Presented]-shell and [Formula Presented]-shell protons separately on the basis of recent high-energy [Formula Presented] data taken at a four-momentum transfer squared [Formula Presented] of 1.1 [Formula Presented] As the resulting average value of the nuclear transparency, [Formula Presented] is considerably higher than the value obtained from previous analyses and theoretical estimates, the high [Formula Presented] data were used instead for an independent determination of the spectroscopic strength for [Formula Presented] knockout. Combining these results with the low [Formula Presented] 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 quasiparticle concept at high [Formula Presented] are discussed as well.