Abstract
We study knockout reactions with proton probes within a theoretical framework where ab initio Quantum Monte Carlo (QMC) wave functions are combined with the Faddeev/Alt-Grassberger-Sandhas few-body reaction formalism. QMC wave functions are used to describe 12C, yielding, for the first time, results consistent with the experimental root mean square (rms) point proton radii, (p,2p) total cross section data, as well as momentum distributions compatible with electron scattering data analysis. In our results for A≤12 and (N−Z)≤3 nuclei the ratios between the (i) theoretical cross sections evaluated using QMC and simple Shell Model structure inputs, and (ii) the corresponding ratios between the spectroscopic factors, summed over states below particle emission, are smaller than unity, pointing to the shortcomings of the simple Shell Model. This quenching is more significant for the knockout of the more correlated nucleon of the deficient species. These ratios can be represented reasonably well by a linear combination of the separation energy and the difference between the removed nucleon rms radius in the parent and residual nuclei, showing a mild dependence on these physical quantities.
Highlights
The mean field approach (MFA) to particle systems has played an important role in atomic physics for describing the periodic table of elements and in nuclear physics for explaining many properties of nuclei, such as the origin of the magic numbers leading to additional stability
We show the inadequacy of the MFA to describe (p,pN) reactions due to contributions in the parent nucleus wave function of many-body partitions beyond the (A−1) + N, the only present in the MFA
Nuclear correlations are a key ingredient and, structure many-body effects must be taken into account
Summary
A formidable theoretical effort has been performed in developing many body and cluster approaches to describe nuclei and their application in the study of reactions [1, 2, 3, 4, 5, 6, 7]. Strong deviations between these models and the MFA indicate the presence. For more than 30 years an extensive experimental program, in particular nucleon knockout reactions with electron and nuclear probes, has been devoted to the study of the failure of the MFA [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22] Many body ab initio calculations of nuclear structure have demonstrated the need to go beyond the simplified MFA and to consider models with explicit nucleon-nucleon (NN) and threenucleon (NNN) interactions and NN and NNN correlations [1, 2], in particular neutron-proton correlations entirely absent in the MFA [8, 9].
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