Low-energy spectra of selected nuclei

In this section, we present a short overview of results obtained using the NCCI approach. Since the model is based on simultaneous isospin and angular-momentum projections, it is particularly well suited to study $N\approx Z$ nuclei. These nuclei are of paramount importance for stringent many-body tests of the weak sector of the Standard Model [29,36]. Besides, they show specific structural features, like the Wigner energy or Nolen-Schiffer anomaly, which are difficult to reproduce within state-of-the-art nuclear models, in particular those rooted in a standard DFT.

A major goal of this work is to pin down strong and weak points of the NCCI approach proposed here. Hence, instead of performing a detailed study of a single nucleus, with many configurations being mixed, we decided to use a modest number of configurations and apply the model to a rather broad set of nuclei, starting from very light systems like $^{6,8}$Li up to $^{62}$Zn. By adding additional configurations, the present results can certainly be refined. We believe, however, that such refinements will not affect the physical conclusions drown in this work.

To efficiently track the MF configurations and to improve convergence properties of self-consistent calculations, all reference states used in the NCCI calculations below were determined assuming the conservation of parity and signature symmetries. For the $A\leq 42$($A=62$) nuclei, we employed the s.p. basis consisting of $N=10(12)$ spherical harmonic oscillator shells, respectively.