Nucleon-nucleon correlations and the single-particle strength in atomic nuclei

Abstract

We propose a phenomenological approach to examine the role of short-and long-range nucleonnucleon correlations in the quenching of single-particle strength in atomic nuclei and their evolution in asymmetric nuclei and neutron matter. These correlations are thought to be the reason for the quenching of spectroscopic factors observed in (e, e p), (p, 2p) and transfer reactions. We show that the recently observed increase of the high-momentum component of the protons in neutronrich nuclei is consistent with the reduced proton spectroscopic factors. Our approach connects for the first time results on short-range correlations from high-energy electron scattering experiments with the quenching of spectroscopic factors and addresses quantitatively this intriguing question in nuclear physics. We also speculate about the nature of a quasi-proton (nuclear polaron) in neutron matter and its kinetic energy, an important quantity for the properties of neutron stars.

Green's Function Techniques for Infinite Nuclear Systems

“…For the characteristic isospin asymmetry in the interior of nuclei (η = 0.2), the change in occupation below the Fermi surface is of the order of only a few percent. Overall, this shallow asymmetry dependence is at odds with some of the past and recent experimental analysis in both electron-and hadron-induced knock-out reactions [85,87,91]. Importantly, however, these calculations at fixed density do not account for the density and isospin-asymmetry dependence within nuclei, which is likely to be relevant for the description of nuclear momentum distributions.…”

“…One can draw several conclusions from this analysis. The isospin dependence of short-range correlations can be predicted with SCGF techniques and appears to be less pronounced in bulk systems than it is in finite nuclei [66,67,85,87]. The cutoff dependence of the results in isospin asymmetric systems affects more the single-particle properties of protons than those of neutrons.…”

“…It is likely that the tensor component preferentially acts in relatively highmomentum pairs and provides the physical mechanism behind these strong isophobic correlations [66,84]. Extending the np dominance picture to isospin imbalanced systems would naively indicate that protons should be more correlated than neutrons in neutron-rich systems, although quantitative statements depends sensitively on the definition of a correlation measure [85][86][87]. In the astrophysical context, the strong modification of the proton spectral function in isospin asymmetric nuclear matter predicted by SCGF simulations has been explicitly explored at the level of the symmetry energy in [88][89][90].…”

Quasi-free scattering in inverse kinematics as a tool to unveil the structure of nuclei

“…This effect has been studied recently by employing a phenomenological model in Ref. [77] in comparison to experimental (e, e p) and ( p, 2 p) results; see Fig. 12.…”

“…Data points show the quenching factors obtained from (e, e p) and ( p, 2 p) QFS experiments. The figure is reprinted from Ref [77].…”