Spectroscopic factor calculations in the \textit{ab initio} no-core shell model

TL;DR

This study investigates the convergence behavior of spectroscopic factors in the extit{ab initio} no-core shell model for light isotopes, revealing challenges in their convergence and implications for reaction cross-section calculations.

Contribution

It provides the first detailed analysis of spectroscopic factor convergence in the no-core shell model using chiral forces, highlighting their independence from nuclear interactions.

Findings

Spectroscopic factors do not show clear convergence trends.

Low-lying energy spectra converge well with increasing model space.

Using no-core shell model spectroscopic factors for reaction cross-sections may be unreliable.

Abstract

The convergence properties of spectroscopic factors in the \textit{ab initio} no-core shell model are hereby investigated. For this, we consider nuclear energies and spectroscopic factors in $A = 6$ and 7 isotopes, using the chiral forces NNLO$_{\rm opt}$ and N$^3$LO. While low-lying spectrum energy demonstrates remarkable convergence with the increase of model space within the no-core shell model, the spectroscopic factor exhibits no definitive convergence trend and seems independent of the employed nuclear interaction. The use of spectroscopic factors issued from the no-core shell model to calculate cross-sections of knockout reaction might then be questionable. The results are compared with that of the standard shell model and \textit{ab initio} Monte Carlo calculations.