Chiral NNLO$_{\text{sat}}$ descriptions of nuclear multipole resonances within the random phase approximation

TL;DR

This paper investigates nuclear multipole resonances using chiral potentials within the random phase approximation, highlighting the potential and limitations of NNLO_sat and V_low-k in describing experimental data.

Contribution

It demonstrates the application of NNLO_sat to nuclear resonances and analyzes the cutoff dependence of V_low-k, revealing the importance of three-body forces.

Findings

NNLO_sat reasonably reproduces observed resonances.

V_low-k's cutoff dependence affects resonance descriptions.

Predicted low-energy quadrupole resonances in neutron-rich oxygen isotopes.

Abstract

We study nuclear multipole resonances in the framework of the random phase approximation using the chiral potential NNLO$_{\text{sat}}$. This potential includes two- and three-body terms that has been simultaneously optimized to low-energy nucleon-nucleon scattering data and selected nuclear structure data. Our main foci have been the isoscalar monopole, isovector dipole, and isoscalar quadrupole resonances of the closed-shell nuclei, $^4$He, $^{16,22,24}$O, and $^{40,48}$Ca. These resonance modes have been widely observed in experiment. In addition, we use a renormalized chiral potential $V_{\text{low-}k}$, based on the N$^3$LO two-body potential by Entem and Machleidt [Phys. Rev. \textbf{C68}, 041001 (2011)]. This introduces a dependency on the cutoff parameter used in the normalization procedure as reported in previous works by other groups. While NNLO$_{\text{sat}}$ can reasonably reproduce observed multipole resonances, it is not possible to find a single cutoff parameter for the $V_{\text{low-}k}$ potential that simultaneously describe the different types of resonance modes. The sensitivity to the cutoff parameter can be explained by missing induced three-body forces in the calculations. Our results for neutron-rich $^{22,24}$O show a mixing nature of isoscalar and isovector resonances in the dipole channel at low energies. We predict that $^{22}$O and $^{24}$O have low-energy isoscalar quadrupole resonances at energies lower than 5 MeV.