Finite nuclei in an extended Nambu-Jona-Lasinio model

TL;DR

This paper introduces an extended Nambu-Jona-Lasinio (eNJL) model to study finite nuclei, incorporating quark degrees of freedom and chiral symmetry breaking, and compares its predictions with experimental nuclear data.

Contribution

The work develops a unified eNJL framework for finite nuclei, baryonic, and quark matter, including pairing correlations and systematic property analysis.

Findings

Reproduces binding energies with RMS deviation of 5.38 MeV for 2495 nuclei.

Charge radii are systematically smaller than experimental values by 0.127 fm.

Identifies shell gap issues at certain magic numbers affecting accuracy.

Abstract

We propose a new theoretical framework to investigate the properties of finite nuclei based on an extended Nambu-Jona-Lasinio (eNJL) model, where the Dirac sea, the spontaneous chiral symmetry breaking, and the quark degrees of freedom are considered by extending the SU(3) NJL model and treating baryons as clusters of quarks. The eNJL model can then be readily adopted to examine the matter states ranging from baryonic matter to quark matter in a unified manner. In this work, by assuming spherically symmetric finite nuclei and neglecting the center-of-mass or rotational corrections, we systematically investigate the properties of finite nuclei based on the eNJL model with additional pairing correlations. It is found that our model generally reproduces the binding energies of the 2495 nuclei ($A>2$) from the 2016 Atomic Mass Evaluation (AME2016) with the root-mean-square deviations $5.38$ MeV. The deviations are mainly attributed to the too large shell gaps at magic numbers $N(Z) =28$, 50, and 82 as well as the spurious shell closures at $N(Z)=34$, 58, and 92. Meanwhile, the obtained charge radii of 906 nuclei are systematically smaller than the experimental values with root-mean-square deviations $0.127$ fm. In our future study, we expect to reduce the uncertainties of our predictions by carefully calibrating the density dependence of coupling constants and considering deformations with microscopic collective corrections from the nucleons in the Fermi sea and quarks in the Dirac sea.