Microscopic description of translationally-invariant core+N+N overlap functions

Abstract

We derive expressions for core + N + N overlap integrals starting from microscopic wave functions obtained in the ab initio no-core shell model. These overlap integrals correspond to three-body channel form factors and can be used to investigate the clustering of many-body systems into a core plus two nucleons. We consider the case when the composite system and the core are described in Slater determinant, harmonic oscillator bases, and we show how to remove spurious center of mass components exactly in order to derive translationally-invariant overlap integrals. We study in particular the Borromean 6He nucleus using realistic chiral nuclear interactions, and we demonstrate that the observed clusterization in this system is a Pauli focusing effect. The inclusion of three-body forces has a small effect on this structure. In addition, we discuss the issue of absolute normalization for spectroscopic factors, which we show is larger than one. As part of this study we also perform extrapolations of ground-state observables and investigate the dependence of these results on the resolution scale of the interaction.

Revised manuscript version; accepted for publication as a Rapid Communication in Physical Review C. Changed title, added some results, corrected errors in figure 4 and table II, updated introduction and references. 12 pages, 4 figures

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• Nucleon-$\alpha$ Scattering and Resonances in ${}^5$He and ${}^5$Li with JISP16 and Daejeon16 $NN$ interactions
• Energy Spectrum of Neutron-Rich Helium Isotopes: Complex Made Simple
• Natural orbitals for the ab initio no-core configuration interaction approach
• Properties of infrared extrapolations in a harmonic oscillator basis
• Systematic study of infrared energy corrections in truncated oscillator spaces
• Two-dimensional extrapolation procedure for ab initio study of nuclear size parameters and the properties of halo nucleus 6He