Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

TL;DR

This study uses self-consistent Green's function theory to analyze how chiral three-nucleon forces influence spectral properties, radii, and shell evolution in oxygen isotopes, revealing their subtle but crucial role in nuclear structure.

Contribution

It introduces a comprehensive SCGF approach with Dyson-ADC(3) and Gorkov-SCGF formalisms to assess 3NFs effects on oxygen isotopes, highlighting their impact on energy levels and shell evolution.

Findings

Spectroscopic factors are minimally affected by 3NFs.

Calculated matter radii are smaller than experimental values.

3NFs primarily fine-tune quasiparticle energies and shell structure.

Abstract

The impact of three-nucleon forces (3NFs) along the oxygen chain is investigated for the spectral distribution for attachment and removal of a nucleon, spectroscopic factors and matter radii. We employ self-consistent Green's function (SCGF) theory which allows a comprehensive calculation of the single particle spectral function. For the closed subshell isotopes, $^{14}$O, $^{16}$O, $^{22}$O, $^{24}$O and $^{28}$O, we perform calculations with the Dyson-ADC(3) method. The remaining open shell isotopes are studied using the newly developed Gorkov-SCGF formalism up to second order. We produce plots for the full-fledged spectral distributions. The spectroscopic factors for the dominant quasiparticle peaks are found to depend very little on the leading order (NNLO) chiral 3NFs. The latters have small impact on the calculated matter radii, which, however are consistently obtained smaller than experiment. Similarly, single particle spectra tend to be diluted with respect to experiment. This effect might hinder, to some extent, the onset of correlations and screen the quenching of calculated spectroscopic factors. The most important effects of 3NFs is thus the fine tuning of the energies for the dominant quasiparticle states, which govern the shell evolution and the position of driplines. Although present chiral NNLO 3NFs interactions do reproduce the binding energies correctly in this mass region, the details of the nuclear wave function remain at odd with the experiment showing too small radii and a too dilute single particle spectrum, similar to what already pointed out for larger masses. This suggests a lack of repulsion in the present model of NN+3N interactions which is mildly apparent already for masses in the A=14--28 range.